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10 Biological Psychology Examples

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Biological psychology involves studying biological influences on behavior, thoughts, and emotions (Kalat, 2015).

Biological psychology primarily focuses on the nervous system, hormones, and genetics. These biological influences are intertwined with each other and environmental influences, making the path from biology to behavior highly complex.

This specialty within psychology may use both human and animal-model research methods . 

This is a rapidly growing and changing field. As scientific techniques advance and become cheaper, more researchers can use innovative methods to understand biological processes involved in various behavioral outcomes, including mental health, cognition and learning, and much more (Lyons et al., 2014).

Note: Biological psychology is sometimes called biopsychology, physiological psychology, and psychobiology (APA, 2024) .

Definition of Biological Psychology

Biological psychology is a broad field that seeks to identify biological explanations of behavior (Kalat, 2015).

Biological psychology suggests that humans think and act the way we do because of brain mechanisms and activity.

A critical concept in biological psychology is that perception occurs in your brain (Kalat, 2015).

For example, if you accidentally touch a hot stove, the nerves in your hand send a signal to your brain. So, you feel that burn in your brain, not your hand. This applies to more than just pain but also other modes of perception, like vision.

Biological psychology is concerned with both proximate and ultimate questions:

• Proximate questions concern immediate and mechanistic influences on behavior,
• Ultimate questions concern larger historical and evolutionary influences (Lyons et al., 2014).

Biological psychology encompasses research methods, including studying behavior concerning brain activity, hormones, and genetics.

• The study of brain activity . A scientist is interested in understanding how the brain operates while someone is reading. This scientist may design an fMRI study and have people complete a specific reading task while in the scanner. Then the scientist can see what regions of the brain activate while someone is reading.
• Lesion studies . Lesion studies were prevalent in early biological psychology and neuroscience. These studies looked for associations between damage or abnormalities in brain tissue and behavior. A classic example is Phineas Gage. Gage experienced major damage to his frontal lobe in a construction accident. He survived, but his personality changed, and he lost his ability to self-regulate and inhibit his impulses . Scientists studied Gage and began understanding that the frontal lobe was important to personality and self-regulation.
• The study of hormones . Biological psychology can concern with how hormones influence behavior. Hormones are chemical messengers that are released by specific glands and travel in the bloodstream. Hormone levels can be increased or decreased by specific situations. For example, cortisol, a stress hormone, may increase in a frightening situation and influence behavior by impacting your attention.   
• Twin Studies . Twin and family studies provide an aggregate estimate of genetic influences on variability in behavioral or psychological outcomes by examining differences between people who share different amounts of DNA. For example, early twin and family research was important to understanding that a significant genetic component played a role in why some people develop schizophrenia (Knopik et al., 2016). In addition, twin studies consistently found that genetic and environmental influences are important to almost all human behavior.    
• GWAS . GWAS are a recent and popular development in biological psychology. GWAS findings have backed up much of the twin and family literature. GWAS have also made large advances in our understanding of genetics and behavior. For example, GWAS have demonstrated that many (sometimes thousands) genes have tiny effects, on behavior, rather than a few genes having large effects.    
• Epigenetics . Epigenetics is another method used in biological psychology. Epigenetics is concerned with gene regulation and expression, specifically methylation. Environmental factors , like poverty, can impact methylation and gene expression. For example, researchers have found that people who have experienced poverty have faster biological aging, indicated by DNA methylation (Raffington & Belsky, 2022).    
• Asking Proximate Questions . Proximate questions deal with immediate and mechanistic influences on behavior. For example, a hormone researcher may be interested in the link between puberty and mental health. They think specific hormones that increase in puberty, like testosterone in males, may partially explain the increase in mental health issues or risk-taking behavior observed in teenage boys. If the researcher found a connection between testosterone and aggression, that would be a proximate explanation. 
• Animal-models . Researchers can use animal-models, like rat or mouse models, to examine questions related to biology and behavior. For example, researchers can alter the genetic makeup of a model-animal, expose the animals to specific environmental influences and examine DNA methylation, or perform lesion studies. 
• Studying candidate genes and false positives . Not all research methods in biological psychology have stood the test of time. Candidate gene studies were popular when psychologists first started using measured genetics in their research. Unlike the GWAS, candidate gene studies would typically look at if one specific gene related to behavior. We now know that single genes have very tiny effects on behavior. Candidate gene studies were particularly popular in gene by environment studies (GxE), where researchers examine if the effect of a gene or genetic influences depends on environmental contexts. Though twin studies have demonstrated GxE, researchers have shown that many candidate GxE findings were likely false positives (Duncan & Keller, 2011).   
• Working in correlation studies . Biological psychology requires careful interpretation because a great deal of the studies explore correlations (not causations). For example, a researcher may find that specific brain structure differences are related to differences in depression symptoms. However, this doesn’t tell us that that brain region causes depression.

Common Biological Psychology Research Methods & Tools

1. brain imaging.

There are several brain imaging techniques used in biological psychology. These techniques can provide information about the brain’s structure or function (activity) (Lyons et al., 2014).

Techniques that provide information about the brain’s structure include CT scans and magnetic resonance imaging (MRI). Functional techniques that infer brain activity include PET scans and functional MRI (fMRI).

2. Electrophysiological Tools

Biological psychology also relies on electrophysiological tools to directly measure the activity of either single nerve cells or large groups of nerve cells. One of the most popular electrophysiological techniques is electroencephalography (EEG).  

3. Behavioral Genetics

Biological psychology also relies on measuring genetic makeup or hormone levels and seeing if those influences correlate with specific behavioral and psychological outcomes. The study of genetic and environmental influences on behavior is known as behavioral genetics and is also sometimes called sociogenomics (Harden, 2021).

Behavioral genetics typically uses either twin/family studies or genome-wide association studies (GWAS) to understand how genetic and environmental influences contribute to variability in human behavior and psychological outcomes (Harden, 2021).

Twin studies compare how similar identical and fraternal twins are on a specific outcome and then use specific statistical models to estimate genetic and environmental influences on that outcome. GWAS involves testing correlations between an outcome and many measured genetic differences across the genome.

Other Types of Psychology

• Evolutionary Psychology – Evolutionary psychology aims to understand how thoughts, actions, and behavior are shaped by evolutionary forces (Mealey, 2023; Workman, 2004).
• Clinical Psychology – Clinical Psychology is a specialty in psychology that involves the practical application of psychological theories for treating psychological problems and disorders (Pomerantz, 2016).

Biological psychology is concerned with biological explanations and influences of human behavior. Though biological psychology uses impressive and advanced tools, it is important to remember that most of the work is still correlational, and it is very hard to identify true causation.

APA Dictionary of Psychology . (n.d.). Retrieved January 23, 2023, from https://dictionary.apa.org/

Duncan, L. E., & Keller, M. C. (2011). A Critical Review of the First 10 Years of Candidate Gene-by-Environment Interaction Research in Psychiatry. American Journal of Psychiatry , 168 (10), 1041–1049. https://doi.org/10.1176/appi.ajp.2011.11020191

Harden, K. P. (2021). “Reports of My Death Were Greatly Exaggerated”: Behavior genetics in the postgenomic era. Annual Review of Psychology , 72 (1), null. https://doi.org/10.1146/annurev-psych-052220-103822

Kalat, J. W. (2015). Biological Psychology . Cengage Learning.

Knopik, V. S., Neiderhiser, J. M., DeFries, J. C., & Plomin, R. (2016). Behavioral Genetics (Seventh edition). Worth Publishers.

Lyons, M., Harrison, N., Brewer, G., Robinson, S., & Sanders, R. (2014). Biological Psychology . Learning Matters.

Raffington, L., & Belsky, D. W. (2022). Integrating DNA Methylation Measures of Biological Aging into Social Determinants of Health Research. Current Environmental Health Reports , 9 (2), 196–210. https://doi.org/10.1007/s40572-022-00338-8

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Biopsychology

Biopsychology is a branch of psychology that analyzes how the brain, neurotransmitters, and other aspects of our biology influence our behaviors, thoughts, and feelings.

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Jean Piaget's theory of cognitive development suggests that children move through four different stages of intellectual development which reflect the increasing sophistication of children's thoughts. Child development is determined by biological maturation and interaction with the environment.

Learn More: Piaget's Stages of Cognitive Development

Behaviorism is a theory of learning that states all behaviors are learned through interaction with the environment through a process called conditioning. Thus, behavior is simply a response to environmental stimuli.

Learn More: Behaviorist Approach in Psychology

Sigmund Freud (1856 to 1939) was the founding father of psychoanalysis, a method for treating mental illness and a theory that explains human behavior. His theories are clinically derived, based on what his patients told him during therapy.

Learn More: Sigmund Freud's Influence on Psychology

An approach is a perspective that involves certain assumptions about human behavior: the way people function, which aspects of them are worthy of study, and what research methods are appropriate for undertaking this study. The five major psychological perspectives are biological, psychodynamic, behaviorist, cognitive, and humanistic.

Learn More: Major Perspectives in Modern Psychology

Neuroscience is the branch of science concerned with studying the nervous system. It is a multidisciplinary field integrating numerous perspectives from biology, psychology, and medicine. It consists of several sub-fields ranging from the study of neurochemicals to the study of behavior and thought.

Learn More: What is Neuroscience?

Frequent Asked Questions

Is psychodynamic same as psychoanalytic?

The words psychodynamic and psychoanalytic are often confused. Remember that Freud’s theories were psychoanalytic, whereas the term ‘psychodynamic’ refers to both his theories and those of his followers, such as Carl Jung, Anna Freud, and Erik Erikson.

Learn More: Psychodynamic Approach

What is developmental psychology?

Developmental psychology is a scientific approach which aims to explain how thinking, feeling, and behavior change throughout a person’s life. A significant proportion of theories within this discipline focus upon development during childhood, as this is the period during an individual’s lifespan when the most change occurs.

Learn More: Developmental Psychology

What is Freud’s psychosexual theory?

Sigmund Freud proposed that personality development in childhood takes place during five psychosexual stages, which are the oral, anal, phallic, latency, and genital stages.

During each stage, sexual energy (libido) is expressed in different ways and through different body parts.

Learn More: Freud’s Psychosexual Stages of Development

What Is object permanence in Piaget’s theory?

Object permanence means knowing that an object still exists, even if it is hidden. It requires the ability to form a mental representation (i.e. a schema) of the object.

The attainment of object permanence generally signals the transition from the sensorimotor stage to the  preoperational stage of development .

Learn More: What Is Object Permanence According To Piaget?

What is the difference between a psychology and sociology?

Psychology studies the mind of an individual to understand human behavior and social and emotional reactions, whereas sociology looks beyond individuals and examines societal institutions and groups of people.

Learn More: Similarities and Differences Between Sociology and Psychology

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Biological Psychology

Michael J. Hove, Fitchburg State University

Steven A. Martinez, Temple University

Copyright Year: 2024

Publisher: ROTEL

Language: English

Formats Available

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Learn more about reviews.

Reviewed by Jay Schwartz, Assistant Professor, Western Oregon University on 6/25/24

It is impossible to adequately cover all areas of biopsychology in a single text, and some key areas such as comparative psychology are missing. However, the text recognizes this, and the authors justifiably limit the scope of the text mostly to... read more

Comprehensiveness rating: 4 see less

It is impossible to adequately cover all areas of biopsychology in a single text, and some key areas such as comparative psychology are missing. However, the text recognizes this, and the authors justifiably limit the scope of the text mostly to physiological psychology. Notably lacking are cognitive neuroscience as well as sensation and perception.

Content Accuracy rating: 5

The text is accurate including recognizing where nuance and uncertainty exist.

Relevance/Longevity rating: 4

The text mostly focuses on classic findings which are supported by converging sources of evidence and are very unlikely to be overturned. The chapter on research methods is likely to eventually become outdated, but should remain relevant for the foreseeable future barring major revolutions in technology. Inevitably the text includes statements that certain processes or phenomena are currently not well understood (especially in the later chapters), which may require in some cases extensive revisions as the field progresses.

Clarity rating: 3

Each chapter covers its topic with a lot of detail, but little (note: not zero) explanation or scaffolding. As a result, throughout the text, a student reader might be left overwhelmed or confused about the material, and/or wondering why a given bit of information matters or how it relates to a broader concept. Some chapters (like the chapter on genes) seemed better suited to intro-level students while others (like the chapter on hormones and behavior) included more jargon with less context.

Consistency rating: 5

The text consistently adopts a biological framework in which psychological phenomena are understood as underpinned by physiological activity. It does a good job of conveying this lens to students.

Modularity rating: 4

Subsections are generally brief and easy to assign specific ones based on the instructor’s needs. Chapter sections vary widely in length, with some spanning only 1-2 pages and stating that a particular field of research exists rather than reviewing it.

Organization/Structure/Flow rating: 5

The early chapters cover foundational knowledge such as brain anatomy and basic neurophysiology, while the middle and later chapters cover higher-level and applied topics.

Interface rating: 5

I did notice any interface issues.

Grammatical Errors rating: 5

I did not notice any grammatical errors.

Cultural Relevance rating: 4

The first chapter contains a section explaining the value of diversity in the discipline.

As mentioned above, due to the density of detail in some areas and the lack of scaffolding, students might be left overwhelmed or confused about the material. On the other hand, its brevity makes it easy to get through, and a first exposure to these concepts can help students even if it doesn’t make complete sense to them on a first pass. But if I were using this as the primary text in a course, I would think of lecture as the main avenue for student learning. I could also see this text being very useful as a reference to someone who has already learned this material.

Table of Contents

• Front Matter
• Chapter 1: Introduction to Biological Psychology
• Chapter 2: The Brain and Nervous System
• Chapter 3: Neurons
• Chapter 4: Research Methods in Biological Psychology
• Chapter 5: Psychopharmacology
• Chapter 6: Hormones and Behavior
• Chapter 7: Development of the Brain and Nervous System
• Chapter 8: Genetics and Epigenetics in Psychology
• Chapter 9: Emotion and Affective Neuroscience
• Chapter 10: Brain Damage, Neurodegeneration, and Neurological Diseases
• Chapter 11: Biopsychology of Psychological Disorders
• Grant Information

Ancillary Material

About the book.

Biological psychology is the study of the biological bases of behavior and mental processes. It explores how biological factors like genes, hormones, neurotransmitters, and brain structures influence psychological components like thoughts, emotions, memories, and actions. This free and open textbook provides a wide ranging and up-to-date introduction to the main topics and methods of biological psychology.

About the Contributors

Michael J. Hove is an associate professor of psychology at Fitchburg State University in Massachusetts. He received a PhD in psychology at Cornell and held research positions at the Max Planck Institute and Harvard Medical School. In addition to Biological Psychology, he teaches Sensation and Perception, Cognitive Neuroscience, Stats and Research Methods, and psychology seminars on the Science of Meditation, Music and the Brain, and the Climate Crisis. His research interests include rhythm, music and movement, and altered states of consciousness. In his spare time, he enjoys hiking, playing music and ice hockey, and hanging with his family. When his 4- and 6-year-old boys had a hard time sleeping, reading a few paragraphs from this book would put them right to sleep. Hopefully it’s not so sleep inducing for you.

Steven Martinez is a graduate student in Psychology and Neuroscience at Temple University in Philadelphia, Pennsylvania. He completed his BS at Fitchburg State University and held research positions at Yale University, the University of California San Francisco, and the San Francisco VA Medical Center. As a graduate student, Steven is studying how digital media habits influence decision-making and how rewarding and threatening properties of motivation impact memory. In his free time, he is most likely playing soccer or exploring Philly.

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Pillar II: Biological

Learning objectives.

• Describe the basic interests and applications of biopsychology and evolutionary psychology

Biopsychology—also known as biological psychology or psychobiology—is the application of the principles of biology to the study of mental processes and behavior. As the name suggests, biopsychology explores how our biology influences our behavior. While biological psychology is a broad field, many biological psychologists want to understand how the structure and function of the nervous system is related to behavior. The fields of behavioral neuroscience, cognitive neuroscience, and neuropsychology are all subfields of biological psychology.

The research interests of biological psychologists span a number of domains, including but not limited to, sensory and motor systems, sleep, drug use and abuse, ingestive behavior, reproductive behavior, neurodevelopment, plasticity of the nervous system, and biological correlates of psychological disorders. Given the broad areas of interest falling under the purview of biological psychology, it will probably come as no surprise that individuals from all sorts of backgrounds are involved in this research, including biologists, medical professionals, physiologists, and chemists. This interdisciplinary approach is often referred to as neuroscience, of which biological psychology is a component (Carlson, 2013).

Evolutionary Psychology

While biopsychology typically focuses on the immediate causes of behavior based in the physiology of a human or other animal, evolutionary psychology seeks to study the ultimate biological causes of behavior. Just as genetic traits have evolved and adapted over time, psychological traits can also evolve and be determined through natural selection . Evolutionary psychologists study the extent that a behavior is impacted by genetics. The study of behavior in the context of evolution has its origins with Charles Darwin, the co-discoverer of the theory of evolution by natural selection. Darwin was well aware that behaviors should be adaptive and wrote books titled, The Descent of Man (1871) and The Expression of the Emotions in Man and Animals (1872), to explore this field.

Evolutionary psychology is based on the hypothesis that, just like hearts, lungs, livers, kidneys, and immune systems, cognition has functional structure that has a genetic basis, and therefore has evolved by natural selection. They seek to understand psychological mechanisms by understanding the survival and reproductive functions they might have served over the course of evolutionary history. These might include abilities to infer others’ emotions, discern kin from non-kin, identify and prefer healthier mates, cooperate with others and follow leaders. Consistent with the theory of natural selection, evolutionary psychology sees humans as often in conflict with others, including mates and relatives. For instance, a mother may wish to wean her offspring from breastfeeding earlier than does her infant, which frees up the mother to invest in additional offspring.

Evolutionary psychology, and specifically, the evolutionary psychology of humans, has enjoyed a resurgence in recent decades. To be subject to evolution by natural selection, a behavior must have a significant genetic cause. In general, we expect all human cultures to express a behavior if it is caused genetically, since the genetic differences among human groups are small. The approach taken by most evolutionary psychologists is to predict the outcome of a behavior in a particular situation based on evolutionary theory and then to make observations, or conduct experiments, to determine whether the results match the theory.

There are many areas of human behavior for which evolution can make predictions. Examples include memory, mate choice, relationships between kin, friendship and cooperation, parenting, social organization, and status (Confer et al., 2010).

Evolutionary psychologists have had success in finding experimental correspondence between observations and expectations. In one example, in a study of mate preference differences between men and women that spanned 37 cultures, Buss (1989) found that women valued earning potential factors greater than men, and men valued potential reproductive factors (youth and attractiveness) greater than women in their prospective mates. In general, the predictions were in line with the predictions of evolution, although there were deviations in some cultures.

Sensation and Perception

Scientists interested in both physiological aspects of sensory systems as well as in the psychological experience of sensory information work within the area of sensation and perception . As such, sensation and perception research is also quite interdisciplinary. Imagine walking between buildings as you move from one class to another. You are inundated with sights, sounds, touch sensations, and smells. You also experience the temperature of the air around you and maintain your balance as you make your way. These are all factors of interest to someone working in the domain of sensation and perception.

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model of psychological disorders resulting from the inability of an internal mechanism to perform its natural function

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Biological Psychology

Biological psychology, also known as biopsychology or psychobiology, is a branch of psychology that explores the relationship between the human mind and behavior, and the biological processes and structures of the body.

Biological psychology seeks to understand how psychological phenomena can be explained through physiological processes, such as genetics, neural activity, and biochemical interactions. It investigates how these bodily mechanisms influence human cognition, emotions, motivations, and behavior.

Key Areas of Study

Researchers in biological psychology study various aspects of the human brain and body, including:

• Neurotransmission: Investigating the role of neurotransmitters in information processing and communication within the brain.
• Neuroanatomy: Examining the structure and organization of the nervous system, including the brain, spinal cord, and peripheral nerves.
• Neuroendocrinology: Studying the interaction between the nervous system and hormones, and how they influence behavior and mental processes.
• Genetics: Exploring the role of genes and heredity in determining psychological traits and susceptibility to certain disorders.
• Neuroplasticity: Investigating the brain’s ability to adapt and reorganize itself in response to experiences and environmental changes.

Biological psychologists employ a variety of research methods to examine the biological basis of behavior and mental processes. These methods may include:

• Neuroimaging techniques: Using technologies such as fMRI, PET scans, and EEG to observe brain activity and measure structural and functional changes.
• Animal studies: Conducting experiments on animals to gain insights into processes that are difficult to observe directly in humans.
• Genetic analysis: Examining the role of genes in behavior by studying twins, conducting linkage studies, and analyzing genetic markers.
• Psychophysiological measurements: Assessing physiological responses, such as heart rate, pupil dilation, and skin conductance, to understand emotional and cognitive processes.
• Pharmacological interventions: Administering drugs to manipulate neurotransmitter levels and study their effects on behavior.

Applications

The findings of biological psychology have significant implications in various areas, including:

• Psychopathology: Understanding the biological basis of mental disorders and developing effective treatments.
• Neuropsychology: Investigating the relationship between brain dysfunction and cognitive impairments.
• Biological basis of behavior: Exploring the biological foundations of human behavior, such as aggression, motivation, and addiction.
• Health and well-being: Examining the role of biological factors in promoting physical and mental well-being.
• Developmental psychology: Investigating how biological processes contribute to the growth, maturation, and aging of the brain and behavior.

Overall, biological psychology is an interdisciplinary field that bridges the gap between biology and psychology, aiming to unravel the intricate connections between the mind and body.

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biological psychology

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• Verywell Mind - Studying the Brain and Behavior in Biopsychology

biological psychology , the study of the physiological bases of behaviour. Biological psychology is concerned primarily with the relationship between psychological processes and the underlying physiological events—or, in other words, the mind-body phenomenon. Its focus is the function of the brain and the rest of the nervous system in activities (e.g., thinking , learning, feeling, sensing, and perceiving) recognized as characteristic of humans and other animals. Biological psychology has continually been involved in studying the physical basis for the reception of internal and external stimuli by the nervous system, particularly the visual and auditory systems. Other areas of study have included the physiological bases for motivated behaviour, emotion , learning , memory , cognition , and mental disorders . Also considered are physical factors that directly affect the nervous system , including heredity , metabolism , hormones , disease , drug ingestion, and diet.

Theories of the relationship between body and mind date back at least to Aristotle , who conjectured that the two exist as aspects of the same entity, the mind being merely one of the body’s functions. In the dualism of French philosopher René Descartes , both the mind and the soul are spiritual entities existing separately from the mechanical operations of the human body . Related to this is the psychological parallelism theory of German philosopher Gottfried Wilhelm Leibniz . Leibniz believed that mind and body are separate but that their activities directly parallel each other. In recent times behaviourists such as American psychologist John B. Watson moved away from consideration of the spiritual or mental and focused on observable human and animal behaviours and their relationship to the nervous system. See behavioral science .

Biological Psychology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience, Third Edition

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Biological Psychology

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• Rudi D’Hooge DSc, Ph.D. 3 &
• Detlef Balschun Ph.D. 3  

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Related Terms

Behavioral neuroscience ; Biopsychology ; Cognitive neuroscience ; Physiological psychology ; Psychobiology

Description

Biological psychology can be concisely defined as the scientific study of the biological processes underlying or influencing mind and behavior. In this regard, it is basically a materialistic approach to the human condition since it provides methods and strategies to investigate the natural causes and aims of (human) behavior. It is one of the few scientific disciplines at the crossroad between humanities and natural sciences. Dewsbury (Dewsbury 1991 ) argued that the synonym psychobiology was probably coined at the beginning of the twentieth century, but some authors have dated its first use many years earlier. Some students of biological psychology may have used this term or its synonyms to distance themselves from mainstream psychology, which some find insufficiently based on biology or natural science as a whole. American psychologist Knight Dunlap...

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D’Hooge, R., Balschun, D. (2013). Biological Psychology. In: Runehov, A.L.C., Oviedo, L. (eds) Encyclopedia of Sciences and Religions. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-8265-8_240

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1 Introduction to biological psychology

Professor Pete Clifton

Research at the interface of biology and psychology is amongst the most active in the whole of science. It seeks to answer some of the ‘big’ questions that have fascinated our species for thousands of years. What is the relationship between brain and mind? What does it mean to be conscious? Developments in our understanding of conditions such as depression or anxiety that can severely impact on our quality of life give hope for the development of more effective treatments.

One reason for rapid advances in biological psychology has been the technological progress that has provided tools to study brain processes in ways that were unimaginable just a few decades ago. It easy to forget that it was only 130 years ago, in the late nineteenth century, that Santiago Ramón y Cajal, Camillo Golgi and others were describing the detailed structures of nerve cells in the brain.

In addition to his skill in describing the detailed structure of the nervous system, Cajal made crucial theoretical advances and, for that reason, is often referred to as ‘the father of neuroscience’. He was the first to argue clearly that transmission of the nerve impulse is in one direction only and that individual neurons communicate at specialised structures called synapses. The detailed mechanisms that underlie communication – the nervous system, the action potential, and synaptic transmission – were not elucidated until the 1950s. At about the same time, records of the firing of single cells in the nervous system, especially within those parts of the brain that receive sensory stimuli, began to suggest the way in which information was coded and processed.

At that time the experimental methods for investigating the contribution of particular brain structures to aspects of behaviour were crude. They essentially involved permanently destroying (‘lesioning’) a few square millimetres of brain tissue containing several hundred thousand nerve cells, and then examining the effects on behaviour. Since then, there have been remarkable advances in our ability to study brain mechanisms and their relationship to behaviour. It is now possible to record the activity of many cells simultaneously. There are techniques that permit modulation of the activity of groups of nerve cells with identified functions for a short period of time before allowing them to return to normal functioning. As you will read in later chapters of this book, this has made possible a much greater understanding of the workings of the brain under normal circumstances, and the ways in which its functioning may be disturbed in different disease states.

As you read through this book it may seem as though the brain is a terribly ‘tidy’ organ. That, at least, is the impression that you might easily get as you look at the drawings and pictures that illustrate the text. But it is worth reflecting on how it feels to encounter a soft, jelly-like, living brain in practice. Here are a couple of sentences from the neurosurgeon Henry Marsh, describing the way in which he uses a small suction device to gradually approach, and then remove, a tumour located towards the centre of his patient’s brain. This particular tumour was located in the pineal gland, a structure with a long and fascinating history in neuroscience. He writes:

I look down my operating microscope, feeling my way downwards through the soft white substance of the brain, searching for the tumour. The idea that my sucker is moving through thought itself, through emotion and reason, that memories, dreams and reflections should consist of jelly, is simply too strange to understand. (Do No Harm: Stories of Life, Death and Brain Surgery. Weidenfeld & Nicolson, 2014).

Mind and brain: a historical context

Heart or brain as the basis for thought and emotion.

During much of recorded human history, there was uncertainty about whether the heart or the brain was responsible for organising our behaviour. The early debates on this topic are best recorded in the works of the Greek philosophers, because, to some extent at least, complete texts are available in a way that is not true for most other ancient human civilisations. In the 700 years from about the 5 th century BCE to the 2 nd century CE, the Greeks put forward two contrasting views.

One group of philosophers, of which Aristotle (~350 BCE) is the best known, held that it was the chest, most likely the heart, that was crucial in organising behaviour and thought.

The heart was the seat of the mind, and the brain had no important role other than, perhaps, to cool the blood. In threatening or exciting situations it is changes in heart function that we become consciously aware of, while we have no conscious access to the changes in brain activation that are occurring at the same time. So it is hardly surprising that the heart was ascribed ‘emotional’ and ‘cognitive’ functions, and that it still features in our communication and language in a way that the brain does not. Apologies can be ‘heartfelt’; the universal emoji for affection and love is a heart; Shakespeare has Macbeth conclude that ‘False face must hide what the false heart doth know’ ( Macbeth 1.7.82) as he resolves to murder King Duncan and take the Scottish throne for himself.

In fact, there was a grain of truth in these ideas. Experiments conducted by Sarah Garfinkel and others in the last few years have demonstrated that pressure receptors in the arteries that lead from the heart become active on each heart contraction and can influence the processing of threat-related stimuli (Garfinkel and Critchley, 2016). It isn’t just the heart that can affect the way in which emotionally salient stimuli are processed by humans – abnormal stomach rhythms enhance the avoidance of visual stimuli, such as faeces, rotting meat, or sour milk, that elicit disgust (Nord et al., 2021). It is interesting that William James, whose Principles of Psychology (1890) is regarded as one of the foundational texts of modern psychology, put forward a similar idea in a short paper published in the 1880s (James 1884).

Another group of early Greek writers gave the brain a much more important role, of which Hippocrates and Plato (4 th century BCE) and Galen (2 nd century BCE) are best known. They developed the idea that, since the brain was physically connected by nerves to the sense organs and muscles, it was also most likely the location of the physical connection with the mind. Galen was a physician whose training was in Alexandria. He moved to Rome and frequently treated the injuries of gladiators. He accepted Hippocrates’ argument about the importance of the brain in processing sensory information and generating behavioural responses. The immediate loss of consciousness that could be produced by a head injury confirmed his view. He also performed experiments that demonstrated the function of individual nerves; he showed that cutting the laryngeal nerve, which runs from the brain to the muscles of the larynx, would stop an animal from vocalising. He rejected another earlier belief that the lungs might be the seat of thought, suggesting that they simply acted as a bellows to drive air through the larynx and produce sounds.

In subsequent centuries Galen’s insights were forgotten in much of western Europe, but remained very influential in the Islamic world. Ibn Sina (still sometimes known as Avicenna, the Latinised version of his name) was born in 980 CE, and is generally acknowledged as the greatest of the physicians of the Persian Golden Age. He refined and corrected many of Galen’s ideas. He provided a detailed description of the effects of a stroke on behaviour, and correctly surmised that strokes might either result from  blockages or bursts in the circulation of blood to the brain. He studied patients suffering from a disorder similar to severe depression that, at the time, was called the ‘love disorder’. When treating someone with this ‘disorder’ he used changes in the heart’s pulse rate as a way of identifying the names of individuals that were especially significant to them. He also, as might be expected of a physician, had a detailed knowledge of the effects of plant-derived drugs such as opium, the dried latex from poppy seed heads of which the active component is morphine (Heydari et al., 2013). He knew that it was especially valuable in treating pain, but had serious side effects including suppression of breathing and, with long term use, addiction (see Chapters 6 and 15).

Mind and body

In the intellectual ferment of post-Reformation Europe, the relationship between the mind and body, especially in the context of what we can know with certainty to be true, became a subject of great controversy.

René Descartes was a French philosopher whose most influential work in this area, the Discourse on Method , was published in 1637. He reached the conclusion that we can never be certain that our reasoning about the external world is correct, nor can we be sure that most of our own experiences are not simply dreams. However, he argued, the one thing we can be certain of is that, to use Bryan Magee’s free translation, I am consciously aware, therefore I know that I must exist: ‘Si je pense, donc je suis’   in the original French, or famously ‘ Cogito, ergo sum’  in the later Latin translation (Magee, 1987) .

This became the basis for Descartes’ argument for dualism . However, he also recognised that mind and body had to interact in some way. In his book De homine [About humans] written in 1633 but not published until just after his death, he suggested that this might happen through the pineal gland, as the only non-paired structure within the brain. He also thought that muscle action might be produced through some kind of pneumatic mechanism involving the movement of ‘animal spirits’ from the fluid-filled ventricles within the brain to the muscles. In this scheme, the pineal gland acted as a kind of valve between the mind and the brain. We now know that the pineal gland is in fact an endocrine gland that is important in regulating sleep patterns.

Descartes also described simple reflexes, such as the withdrawal of limb from heat or fire, as occurring via the spinal cord, and not involving the pineal gland (Descartes [1662], 1998). Although many of Descartes’ ideas about the way in which the body functioned were incorrect, he was a materialist, in the sense that he viewed the body as a mechanism.

Descartes’ legend to this drawing (Figure 1.6) reads:

For example, if the fire A is close to the foot B, the small particles of fire, which as you know move very swiftly, are able to move as well the part of the skin which they touch on the foot. In this way, by pulling at the little thread cc, which you see attached there, they at the same instant open e, which is the entry for the pore d, which is where this small thread terminates; just as, by pulling one end of a cord, you ring a bell which hangs at the other end…. Now when the entry of the pore, or the little tube, de, has thus been opened, the animal spirits flow into it from the cavity F, and through it they are carried partly into the muscles which serve to pull the foot back from the fire, partly into those which serve to turn the eyes and the head to look at it, and partly into those which serve to move the hands forward and to turn the whole body for its defense. (de Homine, 1662)

The common feature of both the heart- and early brain-centred ideas about the relationship between the body and behaviour was of a fluid-based mechanism that translated intentions into behaviour. In the brain-centred view, the fluid in the ventricles (Descartes’ ‘animal spirits’) connected to the muscles by nerves had this function, whereas in the heart-centred account, that role was taken by the blood.

Electrical phenomena were documented as long ago as 2600 BCE in Egypt, but it was not until the eighteenth century that they became a subject of serious scientific enquiry. In 1733 Stephen Hales suggested that the mechanism envisaged by Descartes might be electrical, rather than fluid, in nature, although this idea remained very controversial.

By 1791 Luigi Galvani had confirmed electrical stimulation of a frog sciatic nerve could produce contractions in the muscles of a dissected frog leg to which it was connected. He announced that he had demonstrated ‘the electric nature of animal spirits’.

In the 1850s Hermann von Helmholtz used the same frog nerve/muscle preparation to estimate that the speed of conduction in the frog sciatic nerve was about 30 metres per second. This disproved earlier suggestions that the nerve impulse might have a velocity that was as fast as, or even faster, than the speed of light! During the course of the twentieth century, gradual progress was made in understanding exactly how information is transmitted both within and between individual nerve cells. You can read more about this in Chapters 4 and 5.

At about the same time that Galvani and Helmholtz were uncovering the mechanisms of electrical conduction in nerves, there was also great interest in the extent to which different cognitive functions might be localised within the brain. Franz Gall and Johann Spurzheim, working during the first half of the nineteenth century, suggested that small brain areas, mainly located in the cortex, were responsible for different cognitive functions. They also believed that the extent to which individuals excelled in particular areas could be discovered by carefully examining the shape of the skull. Spurzheim coined the term phrenology to describe this technique. The idea became very popular in the early 1800s, but subsequently fell out of favour.

Gall and Spurzheim disagreed spectacularly after they began to work and publish independently. After one book by Spurzheim appeared, Gall wrote: ‘Mr. Spurzheim’s work is 361 pages long, of which he has copied 246 pages from me. …. Others have already accused him of plagiarism; it is at the least very ingenious to have made a book by cutting with scissors’ (Whitaker & Jarema, 2017) .

In the 1860s, studies by physicians such as Paul Broca, working in Paris, began to correlate the loss of particular functions, such as language, with damage to specific areas of the brain. They could only determine this by dissections performed after death, whereas today techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) scans reveal structural changes in the living brain. Studies of this kind could indicate that a particular area was necessary for that ability but did not indicate that they were the only areas of importance. The activation of different brain areas while humans perform both simple and complex cognitive tasks including speech can be measured using functional magnetic resonance imaging (fMRI) while the participant lies in the brain scanner.

Broca also noted that loss of spoken language was almost always associated with a lesion in the left cortex and often associated with weakness in the right limbs – the first clear example of cerebral lateralisation. Although he is usually credited with that discovery, Marc Dax, another neurologist working in the 1830s, appears to have made the same observation as Broca, although his data were not published until after his death in 1865 – just a few months before Broca’s own more comprehensive publication. Although it was assumed until fairly recently that brain lateralisation was uniquely human and associated with language there is now convincing evidence that it is widespread amongst vertebrates and has an ancient evolutionary origin (Vallortigara & Rogers, 2020).

Broca, like so many of the physicians and scientists discussed earlier, was a man of very wide interests. He published comparative studies of brain structure in different vertebrates and used them to support Charles Darwin’s ideas on evolution. He has been criticised for potentially racist views (Gould, 2006). He believed that different human races might represent different species and that they could be distinguished through anatomical differences in brain size and the ratios of limb measurements. Modern genetic studies demonstrate that living humans are a single species, although there is also evidence that early in our evolutionary history our species interbred with other early, and now extinct, humans including Neanderthals and Denisovans (Bergström et al., 2020).

Positivism and the study of behaviour

In the latter part of the nineteenth century, psychologists often relied on introspection for their primary data. But the French philosopher Auguste Compte who led the positivist movement, argued that the social sciences should adopt the same approach as physical scientists and rely solely on empirical observation. In the study of behaviour this meant relying on recording behaviour either in the laboratory or field. North American psychologists studying conditioning and animal learning including John Watson (of ‘Little Albert’ fame – see below) and Burrhus Skinner took this approach. Nikolaas Tinbergen and Konradt Lorenz used a similar framework as they developed the discipline of ethology in Europe.

Behaviorism in North America

Watson, in an article published in Psychological Review in 1913, suggested that ‘Psychology, as the behaviorist views it, is a purely objective, experimental branch of natural science which needs introspection as little as do the sciences of chemistry and physics’  ( Watson, 1913 ).  Watson had a varied scientific career, starting with studies on the neural basis of learning. He was particularly interested in the idea that neurons had to be myelinated in order to support learning. He then spent a year carrying out field studies on sooty and noddy terns using an experimental approach to investigate nest site and egg recognition. This was followed by experimental studies on conditioning using rats, which emphasised the role of simple stimulus-response relationships in behaviour. He resisted any consideration of more complex cognitive processes because, to him, they risked returning to a dualist separation of mind and body.

Towards the end of his short scientific career, he performed the infamous ‘Little Albert’ experiment in which he conditioned a nine-month-old baby, Albert B., to fear a white rat (Watson & Rayner, 1920). Initially, the baby showed no fear of the rat, but the experimenters then made a loud and unexpected sound (a hammer hitting a steel bar) each time the baby reached out towards the rat. After several pairings, Albert would cry if the rat were presented, but continued to play with wooden blocks that he was provided with in the same context. He became upset when presented with a rabbit, though to a lesser extent than with the rat. This is an experiment that would almost certainly not be approved under the ethical codes used in psychology today (see ‘Ethical Issues in Biological Psychology’ later in this chapter).

This type of procedure is now often referred to as Pavlovian conditioning, named after the Nobel prize-winning Russian physiologist Ivan Pavlov. His experiments used dogs and measured salivation in response to the presentation of raw meat. The dogs were conditioned by pairing the sound of a a ticking metronome (not, as often stated, a bell) with the availability of the meat. Subsequently the sound of the metronome alone was enough to elicit salivation. Although Pavlov’s name is the one associated with the phenomenon, it was already well known by his time. The French physiologist Magendie described a similar observation in humans as early as 1836.

Skinner set out an even more radical approach in his book The Behaviour of Organisms (1938), arguing that cognitive or physiological levels of explanation are unnecessary to understand behaviour. In the Preface added to the 1966 edition, he wrote the following:

The simplest contingencies involve at least three terms – stimulus, response, and reinforcer – and at least one other variable (the deprivation associated with the reinforcer) is implied. This is very much more than input and output, and when all relevant variables are thus taken into account, there is no need to appeal to an inner apparatus, whether mental, physiological, or conceptual. The contingencies are quite enough to account for attending, remembering, learning, forgetting, generalizing, abstracting, and many other so-called cognitive processes.

Yet this approach had already been criticised. Donald Hebb, in The Organisation of Behavior, published in 1949, argued for a close relationship between the study of psychology and physiology. In the opening paragraphs of his book he contrasted his own approach with that of Skinner, saying:

A vigorous movement has appeared both in psychology and psychiatry to be rid of ‘physiologising’ that is, to stop using physiological hypotheses. This point of view has been clearly and effectively put by Skinner (1938), …… The present book is written in profound disagreement with such a program for psychology. (Hebb, 1949, page xiv of the Introduction).

Today Hebb is best remembered for the suggestion that learning involves information about two separate events, converging on a single nerve cell, and the connections being strengthened in such a way as to support either Pavlovian or operant conditioning. His hypothesis, which he acknowledged as having its origin in the writings of Tanzi and others some fifty years before, is often remembered by Carla Schatz’ mnemonic ‘Cells that fire together, wire together’. Today, that phrase is most often associated with the phenomenon of long term potentiation (LTP)  which acts as an important model for the neural mechanisms involved in learning and memory.

There were other areas of psychology, especially the study of sensation and perception, where the radical approach of the behaviourists never took a full hold. Helmholtz, whose early work on neural conduction was so important, also made ground breaking contributions to the study of auditory and especially visual perception. He emphasised the importance of unconscious inferences in the way in which visual information is interpreted. All perceptual processing involves a mix of ‘bottom-up’ factors that derive from the sensory input and ‘top-down’ factors which involve our memories and experience of similar sensory input in the past. Alternative, more descriptive, terms for ‘bottom-up’ and ‘top-down’ are data driven and concept driven. You will learn much more about these processes in modules that explore cognitive psychology.

The development of ethology in Europe

Although the study of animal learning during the mid twentieth century was a dominant paradigm in biological psychology in North America, this was much less true in Europe. Here, an alternative approach evolved.

Konrad Lorenz and Nikolaas Tinbergen emphasised the detailed study of animal behaviour, often in a field rather than a laboratory setting. Both were fascinated by natural history when young. Lorenz was especially taken by the phenomenon of imprinting. It was first described in birds, such as chickens and geese, that leave the nest shortly after hatching and follow their parents.   In a classic experiment he divided a clutch of newly-hatched greylag geese into two. One group was exposed to their mother, the other to him. After several days the young goslings were mixed together. When he and the mother goose walked in different directions the group of youngsters divided into two, depending on whom they were originally imprinted. The term imprinting is now often used much more generally for learning that occurs early in life but continues to influence behaviour into adulthood. Lorenz remains a controversial figure because of his association with Nazism during World War II.

Tinbergen began his scientific career in Holland, performing experiments that revealed how insects use landmarks to locate a burrow. They were reminiscent of Watson’s earlier studies with terns, though much better designed. During World War II he was held as hostage but survived and subsequently moved to Oxford University in the late 1940s. He is best remembered for an article written in 1963 on the aims of ethology, which will be the basis of the next section of this chapter.

Lorenz and Tinbergen, like Watson and Skinner, were interested in explaining behaviour in its own terms rather than exploring underlying brain or physiological mechanisms, and in this sense they were both adherents of the positivist approach championed by Auguste Compte for all of the social sciences. Tinbergen made this point very clearly in his book The Study of Instinct (1951). He acknowledges that the behaviour of many other animals can resemble that of a human experiencing an intense emotion (as Darwin had pointed out in The Expression of Emotions in Man and Animals in 1872) but went on to say that ‘because subjective phenomena cannot be observed objectively in animals, it is idle to claim or deny their existence’ (Tinbergen, 1951, p.4).

A cognitive perspective in animal learning and ethology

By the second half of the twentieth century, psychologists interested in human behaviour were becoming increasingly dissatisfied with the limitations of the behaviorist approach. Psychologists working on animal learning also realised that some of the phenomena that could be observed in their experiments could only be explained by postulating intervening cognitive mechanisms. Tony Dickinson, in his short text Contemporary Animal Learning Theory , published in 1980, used the example of sensory preconditioning. Dickinson was one of the initiators of the so-called ‘cognitive revolution’ in animal learning.

In a standard Pavlovian procedure, rats are initially trained to press a bar for small pellets of sweetened food. Then they are exposed to an initially neutral stimulus – a light in the wall of their cage – immediately prior to receiving a mild foot shock. After several such pairings the rats are exposed to the light alone – there is no shock. Nevertheless, the rats ‘freeze’ (remain immobile) and pause bar-pressing for the food reward for a few seconds before returning to their normal behaviour.

The critical modification in sensory preconditioning is to expose the rats to pairings of a light with a second neutral stimulus, in this case a sound, prior to the main conditioning task. Since nothing happened after these initial pairings the rats rapidly come to ignore them. Their ongoing behaviour, in this case bar-pressing for the food pellets, was not changed. Now the rats were conditioned to associate the light and shock in the standard way. Following conditioning they were exposed either to the light, or to the tone. Rats exposed to the tone paused in a similar way to rats that were exposed to the light despite never having experienced that sound preceding a shock. So, despite little or no change in their behaviour during those initial light-tone pairings, they clearly had learned something. Learning does not have to involve any overt behavioural change.

Dickinson set out the implications in the following way:

As we shall see, sensory preconditioning is but one of many examples of behaviourally silent learning, all of which provide difficulties for any view that equates learning with a change in behaviour. Something must change during learning and I shall argue that this change is best characterised as a modification of some internal structure. Whether or not we shall be able at some time to identify the neurophysiological substrate of these cognitive structures is an open question. It is clear, however, that we cannot do so at present. (Dickinson, 1980, p.5)

That was 1980!

As I write this, in the 2020s, it is possible to give an optimistic answer to Dickinson’s final query. Modern techniques from neuroscience can identify the brain structures and changes in small groups of neurons that support learning and memory. In one recent example, Eisuke Koya and his colleagues, who work in the School of Psychology at the University of Sussex, describe a simple learning task in which mice are exposed to a short series of clicks (the ‘to-be-conditioned’ stimulus) followed by an opportunity to drink a small quantity of a sucrose solution. After being exposed to such pairings over a period of a few days, they learn to approach the sucrose delivery port as soon as the clicks begin. The mice used in these experiments were genetically modified in such a way that nerve cells in the frontal cortex that were activated during the conditioning trials could be made to glow with a green fluorescence. The research established that small, stable groups of nerve cells (‘neuronal ensembles’) were activated from one day to the next. The researchers were also able to manipulate these cells in such as way as to produce an abnormal change in their activity during subsequent tests in which the animals were exposed to the conditioned stimulus. Approach to the sucrose delivery port was disrupted when this was done, suggesting that the activation of these cells contributed in an important way to the learnt behaviour of the mouse (Brebner et al., 2020). Experiments of this kind are approaching the goal of identifying the neural structures and mechanisms that support learning and memory, and demonstrate how psychologists and neuroscientists can collaborate to tackle the fundamental problems of biological psychology.

Field studies of non-human primates

Researchers in the field of animal learning were not the only ones who found it difficult to explain their experimental results without invoking cognitive processes that could not be directly observed. Ethologists faced a similar challenge.

Jane Goodall began her fieldwork on chimpanzees in the early 1960s and, as she got to know and was accepted by the troop that she was studying at Gombe Stream in Tanzania, gathered evidence about their rich social and emotional lives and the use of tools that revolutionised studies of primate behaviour. To the consternation of her colleagues at Cambridge, she also gave names to the chimpanzees rather than the numbers which would supposedly lead to more objective study.

At about the same time, Alison Jolly was beginning her studies of lemur behaviour in Madagascar. She argued that the major driving force in evolution of primate cognition came from the complex demands that come from living in complex and long lasting social groups (Jolly, 1966).

Field studies carried out since then have demonstrated long-lasting social relationships in primate species such as baboons and vervet monkeys. Calls that the animals make in the context of aggressive encounters are interpreted in terms of an animal’s prior knowledge of social hierarchies within their group and their prior behaviour. For example, female chacma baboons, studied by Dorothy Cheney and Robert Seyfarth, have a call, the ‘reconciliatory grunt’, that is given just after an aggressive encounter to indicate a peaceful conclusion between the two individuals. When the call was played to a female who had just been involved in a mutual grooming session with another female, she behaved in a way that implied that the call must be directed at someone else and not her. However, if she had been involved in an aggressive encounter with that same female a little earlier, she behaved in a way that implied that the grunt had been directed at her (Engh et al., 2006).

Field studies of other long lived mammals, including elephants and dolphins, suggest that they also have complex social networks and sophisticated cognitive abilities.

Two features stand out at the end of this very short historical survey of ideas about the relationship between the brain and behaviour. The first is that, among contemporary psychologists and neuroscientists, there is an almost universal acceptance of some form of materialism. In other words all of the complexity in our behaviour, including such relatively less well understood areas such as consciousness, are a consequence of physical mechanisms operating in our bodies, and primarily in the nervous system. The second is that, despite a hiatus that lasted for at least the first half of the twentieth century, the study of phenomena such as emotion and consciousness are no longer seen as ‘off limits’ for scientific study. One challenge for modern neuroscience is to understand how the nervous system builds, uses and attaches emotional weight to internal representations of aspects of the external world.

What kinds of questions does Biological Psychology ask?

Since biological psychology is concerned with both behaviour and relevant physiological and brain mechanisms, it will often start with some interesting behavioural observations or experimental data. Once the behaviour of interest has been adequately documented, it is time to ask some questions. The ethologist Niko Tinbergen suggested that were four broad kinds of questions that might be of interest (Tinbergen 1963). The first two have a timescale within the life cycle of an individual animal and are concerned with:

(i) the underlying causes of changes in behaviour, such as brain mechanisms or hormonal changes, and

(ii) the development of behaviour, for example as an individual matures to adulthood.

These are sometimes referred to as the proximate causes of the behaviour. The remaining two questions are set in a much broader time frame and can be thought of as the ultimate causes (Bateson & Laland, 2013). They are concerned with:

(iii) the evolutionary relationships between patterns of behaviour in different species, and

(iv) the advantages of particular patterns of behaviour in the context of natural selection.

A couple of examples should illustrate how these questions differ from one another and yet still address the question of why a particular behaviour occurs in the form that it does.

Example 1: Bird song

The chaffinch ( Fringilla coelebs ) is a common European songbird. In the early Spring, adult males have a striking breeding plumage and their bills darken. At the same time the birds begin to perch in conspicuous places within a small territory that they defend from other males and sing. The females do not sing, although they use a variety of other calls. So, why do male chaffinches sing?

Causes and mechanisms. The changes in bill colour and onset of singing are associated with the increase in day length in the Spring. Experimental studies in other songbird species, such as those by Fenando Nottebohm in canaries, have shown that there is an increase in the secretion of testosterone at this time, and that experimental administration of this steroid hormone produces the same changes in appearance and behaviour (Nottebohm, 2002). Further studies have demonstrated that there are changes in the bird’s brain at this time.

The most surprising result was a clear demonstration that new neurons are formed through cell division in the areas of the brain involved in song. In the mid 1980s, when these studies were performed, the consensus was that neurons were never added to a mature vertebrate brain. Nottebohm’s work forced a re-examination of this idea. The methods that his lab used were repeated in other species, and demonstrated that the same thing could also happen in mammals, including humans. In the years since these ground-breaking studies, a good deal more has been learned about circuits within the songbird brain that support song production.

Development. You do not need to be an experienced birdwatcher to recognise the song of a chaffinch. It consists of several short trills followed a characteristic terminal flourish. This chaffinch sonagram shows the loudness (upper panel) and frequency changes in the song of a chaffinch. Alternatively, play the song as a short video .

However, although it is difficult to mistake the song of a chaffinch for that of a different species, the song has unexpected complexity. An individual may sing several subtly different song types and there are also clear differences in the song over the different parts of their widespread distribution through Europe. This raises several questions about the way in which a young chaffinch develops its song repertoire. If a nestling is reared in an acoustically isolated environment, it develops a highly abnormal song lacking the detailed structure typical of a chaffinch. However, if a bird reared in the same way is exposed to tape-recorded song, then it accurately copies the song types and incorporates them into its repertoire. Of course there will be be a considerable gap between hearing the song as a summer fledgling, and then singing the song in the following spring, so this is another example of behaviourally silent learning. In the wild, things turn out to be be much more complex. A chaffinch may acquire some song types in the first summer, but additional ones may also be learnt from neighbours in the following spring as they set up territories. It is clear that one early, popular idea about the development of song types is incorrect: they are not exclusively learnt from a bird’s father (Riebel et al., 2015).

Evolutionary relationships. Birds, like mammals, reptiles and amphibians, are vertebrates. Although there is tremendous variety in their appearance and behaviour, there are common features, such as the presence of a backbone. There are also strong similarities in broad aspects of brain structure and functioning. Songbirds are one of several groups of living birds and there are some 5000 different species. They all have a well-developed syrinx (the rough equivalent of the human larynx) which has a complex musculature that allows the bird to sing. There is tremendous variation from one species to another, from the complex, extended song of thrushes such as the blackbird and nightingale, to the much simpler song of the chaffinch. Songbirds evolved about 45 million years ago, and birds diverged from the vertebrate line that also gave rise to mammals some 320 million years ago. Our common ancestor probably resembled a small lizard. Present day lizards can show some degree of behavioural flexibility and social learning, so there are interesting questions about the extent to which some of the more advanced cognitive abilities of birds and mammals evolved independently or build on components already present in that common ancestor.

Function or current utility. Song is energetically expensive at a time of the year when food is not at its most abundant. It can also be dangerous. There is a risk that a sparrowhawk will appear over the top of the hedge on which the chaffinch is singing and provide the hawk with its next meal! It follows that song must also potentially enhance the biological fitness of the bird in some way. There are at least two factors at play here. A male has to attract a female to nest in his territory and mate with her. His song also advertises to other males that he holds, or is attempting to hold, that space, and may be a prelude for fighting over ownership of the best areas. There is also experimental evidence that characteristics of the song, particularly the complexity of the final trill, may be attractive to females and lead them to prefer one male over another. Although the evidence is not completely convincing for chaffinches, this idea would fit in with findings from a variety of other species. The croak of a frog, the roar of a red deer stag or the colours of a peacock’s tail may act as signals about the quality of the individual making the call, and may have the advantage of being hard to falsify – so called ‘honest signals’. However the precise way in which such signals evolve remains unclear (Penn & Számadó, 2020; Smith, 1991).

Example 2: Anxiety and fear

Tinbergen’s general approach can be productive in thinking about any aspect of behaviour. In humans anxiety or fear is an unpleasant emotional experience that may come in many forms including panic and phobias of various kinds. The emotion of fear is often evoked by quite specific threat-related stimuli – perhaps a snake (snake phobia) or wide open spaces (agoraphobia). In the same way as for bird song, we can ask the question ‘why?’ and break it down into queries about either proximate or ultimate causes.

Causes and mechanisms. The underlying physiological and brain mechanisms are well studied. They include increases in heart rate, release of hormones such as adrenalin, and activation of a specific brain network that includes the amygdala. One part of the amygdala, the central nucleus, is responsible for activating these different physiological changes in a coordinated manner (LeDoux, 2012). An understanding of these types of mechanisms has clinical relevance. Drugs that act selectively on these threat-processing circuits may have value as treatments for anxiety. Indeed benzodiazepines such as valium  are still widely used in this way and are known to have especially potent effects in the amygdala. An important, but still unanswered, question is how these physiological responses relate to the conscious feeling of fear.

Development. We also know a good deal about the way in which fear may develop during an individual’s lifespan. Simple conditioning may often play a role and there is also good evidence that species as varied as rodents and primates are more likely to become fearful and avoid some types of object rather than others. In social species observational learning may also be important. Studies of young rhesus monkeys illustrate these points. A rhesus infant will initially show little avoidance or fear of model snakes or flowers. However if they are allowed to watch an edited video in which an adult rhesus appears to respond fearfully to either the flowers or a snake, they themselves develop fear responses to the snake but not to the flower (Cook & Mineka, 1990). This suggests an innate tendency to become fearful of some kinds of object, such as a snake, that can potentiate the effects of observational learning. In a similar way many rodent species will avoid odours associated with potential predators such as a fox or cat without having any previous experience of those animals. However, especially when young, those responses may be amplified if they observe an adult responding strongly to the same stimulus.

Evolutionary relationships. Comparative studies of the specific behaviour patterns associated with fear and the underlying physiological and brain mechanisms suggest that they have been conserved through vertebrate evolution. Charles Darwin, in the Expression of the Emotions in Man and Animals, provided some of the first really detailed behavioural descriptions of facial expressions associated with fear and especially emphasised their role in communication. Detailed comparisons of the neural circuitry in mammals, birds, amphibians and reptiles suggest that the amygdala, and especially its connections to the autonomic nervous system which activate the hormonal and other physiological responses to fear-evoking stimuli, are conserved through the entire vertebrate evolutionary line and must therefore have originated at least 400 million years ago. So it is not surprising that one of the responses of a Fijian ground frog to the presence of a potential predator (a cane toad) is an increase in the stress hormone corticosterone as well as a behavioural response, in this case immobility, that reduces the likelihood of being eaten (Narayan et al, 2013). Exposure to a stressful situation in humans produces the same hormonal response, although it is cortisol, which is almost structurally identical to corticosterone, that is released.

Function or current utility. Questions of function, or current utility, can be thought about at multiple levels. It is clear that fear, or the perception of threat-related stimuli can be a powerful driver of learning. As we saw earlier in this chapter, previously neutral stimuli that predict threat or danger come to evoke the same responses as the threat itself (Pavlovian conditioning). In the natural environment such responses are likely to enhance biological fitness. However in addition to thinking about the likely function of fear systems in a rather global manner, it is also possible to analyse the individual behavioural elements that make up a a fear response. One such element, described by Darwin (Darwin, Charles, 1872) and also recognised in the later studies of Paul Ekman, is that the eyebrows are raised which results in the sclera (white) of the eye becoming much more obvious (Jack et al., 2014 includes a video example). The original function of this response may simply have been to widen the field of view but, especially in primates, it can now also serve as a way of communicating fear within a social group. It is likely that behavioural responses frequently gain additional functions during evolution, perhaps even making the original function irrelevant. This is the reason that the term ‘current utility’ is often preferred to function (Bateson & Laland, 2013). If a functional hypothesis is be tested experimentally it will always be current utility that will be assessed. When a particular characteristic or feature acquires additional functions in this way they are sometimes described as exaptations rather than adaptations.

Scientific strategies in Biological Psychology

The first phase of any scientific investigation is likely to be descriptive. In biological psychology, this is a point at which the influence of an ethological approach is most obvious. It is easiest to describe how this phase proceeds by using some specific examples. Once the behaviour of interest has been clearly characterised it is often time to collect some empirical data. This will often involve either collecting behavioural and physiological data and correlating them, or taking a more experimental approach in which environmental or physiological factors are deliberately manipulated. A combination of these approaches will begin to elucidate the way in which neural processes influence behaviour and, in turn, are influenced by the consequences of that behaviour.

Describing behaviour: facial expressions and individual variation during conditioning

Many mammals, including rodents and primates, (including humans in the latter category), make distinctive facial expressions as they try out potential food sources. Humans will lick their lips as they eat something sweet and gooey. A food or drink that is unexpectedly sour (like pure lemon juice) or bitter (perhaps mature leaves of kale or some other member of the cabbage family) might elicit a gaping response in which the mouth opens wide and, in more extreme cases, saliva may drip out of the mouth.

These kinds of response can be observed in quite young babies. Indeed, as any parent is likely to know, they are very common as an infant transitions from breast feeding to solid foods. It may seem surprising but very similar responses can be observed in rats or mice as they drink sweet, sour or bitter solutions. It demonstrates that these are responses that are likely to have been conserved over relatively long periods of evolutionary time. They may serve a dual function. A response like gaping will help to remove something that may be toxic from the mouth – bitterness is often a signal that a plant contains harmful toxins. However it is also likely that, at least in some species, the ‘current utility’ of these expressions also includes a communicative function in species that feed in social groups. This would be another example of an exaptation (i.e. an additional function that becomes adaptive later).

Detailed measurement of these facial responses forms the basis of the so-called ‘taste reactivity task’ in which controlled amounts of solutions with different taste properties are infused into the mouth of a rat or mouse and the facial expressions quantified (Berridge, 2019). The task was initially devised to investigate the role of different brain structures in taste processing. A little later some detailed studies with a variety of different solutions revealed that the extent to which they evoked ingestive (‘nice’) and aversive (‘nasty’) responses could, at least to some extent, vary independently. It then became clear that there were drug and brain manipulations that had no effect on the facial expressions evoked by a liked, or rewarding, sweet solution. However those same manipulations did reduce the extent to which an animal would be prepared to work (e.g. press a lever, perhaps several times) in order to gain access to that solution. The important implication was that the extent to which something is ‘liked’, measured by facial expressions, may depend on different factors to those that affect whether it is ‘wanted’, measured by effort to obtain that reward. Although this distinction first arose in the investigation of what might seem an obscure corner of biological psychology, it has, as you will read in Chapter 15, Addiction , become an important theoretical idea that helps explain some otherwise puzzling features of addiction to drugs, food and other rewarding stimuli.

One feature of animal behaviour, humans included, that seem irritating at first is that there is often substantial variation between individuals exposed to the same experimental manipulation. It can be tempting to ignore it, or to choose measures that at least minimise it. But this can be a mistake, as this example from Pavlovian conditioning demonstrates.

As a group of rats learns the association between the illumination of light and the delivery of a food pellet they retrieve the pellet more rapidly and the averaged behaviour of the group generates a smooth ‘learning’ curve. However, careful observation of individuals reveals several things. First, the changes in individual animals are much more discontinuous – almost as though at some point, individual rats ‘get’ the task, but at different times during the training process! The behaviour of individuals also varies in other, potentially interesting, ways. Some rats approach the light when it illuminates, rearing up to investigate it, and continue to do so even when they subsequently approach the place where the pellet is delivered. Other rats move immediately to the location where the food pellet will be delivered, apparently taking no further interest in the light. The behaviour of the former group is referred to as ‘sign tracking’ and the latter as ‘goal tracking’. It turns out that sign trackers and goal trackers differ in other interesting ways. For example, sign-tracking rats show greater impulsivity in other tasks and acquire alcohol self administration more readily. The same kinds of distinction may also show up in human behaviour and predict vulnerability to drug addiction and relapse.

Although the descriptive phase is likely to begin any serious scientific investigation, once interesting observations have been made they are likely to raise the kinds of questions that were discussed in the last section. What are the brain and physiological mechanisms that underlie the behaviour? How do the behaviour patterns develop through lifespan? and so forth. In working out how to tackle such questions there are a number of potential ways forward. They typically use a combination of two general strategies.

Investigational strategies: correlational approaches, and experimental manipulations

One strategy is to observe changes in behaviour, typically in a carefully controlled test situation or using a clearly defined set of behaviour patterns when doing fieldwork, while measuring changes in physiological and brain function that are likely to be relevant. Then, using appropriate statistical techniques, the changes in behaviour and physiology can be correlated together. The second strategy is to deliberately manipulate a test situation in order to determine the extent to which an imposed change in in physiology or brain function leads to a change in behaviour, or a change in behaviours leads to a physiological change.

The issue with the first correlational strategy is that, although the results may suggest that there is some type of causal relationship between behaviour and physiology, they don’t clarify the nature of the relationship. Behaviour A may cause changes in physiological or brain variable B. But equally, the physiology may influence the behaviour. Finally, it may be that there is no direct mechanistic linkage between behaviour and physiology. Instead, some third variable is independently affecting both. A further complication is that there may be important feedback loops that influence the outcome. So, although correlational studies can be very useful, they do have limitations when it comes to their interpretation. The second strategy, involving deliberate experimental manipulation, has a better chance of determining the direction of causation. But it may raise other problems. Deliberately interfering with the functioning of a complex biological system may lead it to respond in unpredictable ways and may also be ethically problematic.

Let’s see how this works in practice by considering the behaviour of red deer during the autumn rutting season. At this time, a successful male deer may establish a ‘harem’ of female deer and defend them against other males. His behaviour makes it more likely that only he will have the opportunity to mate with them, and hence that the resulting offspring would enhance the representation of his genes in the next generation. Females also gain from being in the harem by gaining some protection from harassment by other males, which provides the opportunity to feed in a more uninterrupted way. They may choose the harem of a particular male on the basis of his perceived fitness.

It would first be possible to correlate the gradual increase in aggressive behaviour during the red deer rut with the increasing blood testosterone that occurs during the autumn. It might be tempting to conclude that the increased testosterone level causes the increased level of aggressive behaviour directed at other males. However there are at least two, and perhaps more, possibilities that would need to be excluded first.

First, it is possible that the changes in behaviour and increased testosterone level are triggered independently by some third factor. One alternative would be that decreasing day length acts as that trigger. The day length signal might be detected within the pineal gland (Descartes’ supposed valve from the soul to the body!) and independently trigger both the hormonal and behavioural changes.

A second possibility is that the behavioural changes actually trigger the hormonal change. This isn’t a completely implausible suggestion. Such effects have been documented in a number of mammals, including human (male) tennis players, where testosterone levels increase after a match that they have just won. In the same way, testosterone secretion might be sensitive to whether aggressive encounters between the male deer are won or lost.

An experimental approach can be used to overcome the difficulty in deciding what causes what. In the case of the role of testosterone in aggression, one possible strategy is to remove the source of testosterone and determine whether aggressive behaviour continues. In fact this has been common practice for millennia in managing farmed animals. An intact bull may be very aggressive but castrated male cattle (bullocks) are typically much less so. In experimental animals the specific role of testosterone could be demonstrated by administering the hormone to a castrated animal and showing that aggressive behaviour returns to the expected level. Experiments of exactly this kind have been performed on red deer, and indicate that testosterone does indeed restore rutting behaviour when administered to a castrated male in the autumn. However the effect of the hormone on rutting behaviour is absent when the same treatment is given in the spring, although there is some increase in aggressive behaviour (Lincoln et al., 1972). So, factors like day length and hormone level interact in a more complex way than might be expected.

A similar experimental approach can be taken in relation to the contribution that particular brain structures or identified groups of neurons may make to a specific behaviour pattern. Suppose that we have already discovered, perhaps by making recordings of neural activity, that neurons in a particular structure (let’s call it area ‘X’) become more active while an animal is feeding. How can we demonstrate that those neurons are important in actually generating the behaviour rather than, for example, just responding to consequences of eating food? In other words, how can we determine that activation of area X causes feeding as opposed to feeding causing activation of area X? If stimulation of the nerve cells within area X leads to the animal, when not hungry, beginning to feed on a highly palatable food, then you might assume that demonstrates their critical role – authors reporting such an experiment will often state that the cells in this area are ‘sufficient’ to generate feeding. However this doesn’t show that those same cells are always active in the many other experimental situations in which that animal might begin to feed. In the same way, suppose an animal fails to eat when the cells in that same area X are inactivated. That finding doesn’t demonstrate that these cells are always ‘necessary’ for feeding to occur. For example, suppose the original test situation were eating a palatable food when already sated, the animal might still eat when those same cells were inactivated after they had been deprived of food for a few hours (Yoshihara & Yoshihara 2018). It is also possible that inactivation of those cells might interfere with other types of behaviour, suggesting that they had no unique importance in relation to feeding. This highlights the moral that demonstrating causation, and especially the direction of causation, is rarely easy!

In studies where only correlations have been measured it is tempting for those presenting the research to slip from initially saying that an association has been observed to then discussing the results in terms of a causal mechanism that hasn’t been fully demonstrated. This is something to watch for when critically assessing research publications. It often happens in the discussion of results based on fieldwork when an experimental approach may be much more challenging. A combination of correlational and experimental approaches can also be taken in studying questions about the development of behaviour.

This combination of approaches can be taken in the study of human behaviour and its relationship to particular brain or other physiological changes. However, the experimental approach can be limited by the more significant ethical concerns that may arise. Clinical data has been used since the time of Galen, Ibn Sina, Broca and others to correlate the brain damage that occurs after strokes, or other forms of brain damage, with changes in behaviour. Classic studies include the patient Tan, studied by Broca, where loss of the ability to speak was linked to damage in the left temporal cortex; and Phineas Gage, whose damage to the prefrontal cortex was associated with more widespread changes in behaviour. This last example also provides a cautionary tale. There is an unresolved dispute as to how substantial and permanent Gage’s changes in behaviour actually were, despite the typical clarity of textbook presentations (Macmillan, 2000).

Ethical issues in Biological Psychology

One consequence of our growing appreciation of the potentially rich cognitive and emotional lives of animal species other than humans has been a concern about the ethical position of their use in experimental or observational studies. Psychology as a discipline has also become much more concerned to treat human participants in an ethical manner, ruling out work such as the Little Albert study that we discussed earlier.

What does it mean, to behave a morally or ethically good way? Philosophers have debated this subject since the dawn of recorded human history. One rational approach which synthesises some of the different possible approaches discussed by the psychologist Stephen Pinker is to ‘only do to others what you would be happy to have done to you’ (Pinker, 2021, p. 66 et seq. ). It is rational in the sense that it combines personal self-interest in a social environment but also survives the change in perspective that comes with being the giver or receiver of a particular action. It is also the basis of the moral codes promoted by many of the world’s religions. This type of philosophical approach is consistent with the Code of Human Research Ethics put forward by the British Psychology Society ( BPS Code of Human Research Ethics – The British Psychological Society , 2021 ), which is based on four fundamental principles:

• Respect for the autonomy and dignity of persons
• Scientific value
• Social responsibility
• Maximising benefit and minimising harm

The code goes on to explain how these principles underpin the ways in which experiments are designed, participants treated, and results disseminated. The last three principles also apply in a relatively straightforward way to research that involves non-human animal species. Applying the first principle is more complex and partly dependent on the moral status that humans give to non-humans.

Philosophers take a variety of positions on morality that are often contradictory. However, two important approaches are utilitarianism , which developed from the writings of the English philosopher Jeremy Bentham in the nineteenth century, and a rights-based approach. Bentham, using concepts developed by the French philosopher Helvétius a century earlier, suggested that good actions are ones which maximise happiness and minimise distress: the ‘greatest felicity’ principle. While he recognised that non-human animals might experience pain and distress, he also regarded that as of lesser importance than the wellbeing of humans.

In the twentieth century writers such as Peter Singer and Richard Ryder rejected this ‘human-centred’ approach, terming it ‘speciesism’, by analogy with racism. But nevertheless they accepted, with this modification, the utilitarian approach of Bentham. Within this framework some use of non-human animals may be ethically justified, though every effort must be made to enhance benefits and especially to reduce any negative impact on the lives of the animals used during the course of the studies.

In contrast, Tom Regan has rejected the view that benefits and dis-benefits could be added together using some form of utilitarian arithmetic to decide whether an action was acceptable or not. Instead, he asserted that at least some non-human animals have the same rights as a human to life and freedom from distress. They are, to use his phrase, ‘subjects of a life’. Regan discusses a number of attributes that might help in deciding whether a particular group of animals meet this criterion. Regan’s approach would rule out the use of many species of animal in science, agriculture and many other contexts

The first UK law designed to protect non-human animals used in scientific research was the Cruelty to Animals Act 1876. It was replaced by the Animals (Scientific Procedures) Act 1986 in line with the EU Directive 86/609/EEC ( now replaced by Directive 2010/63/EU ). The legislation takes a broadly utilitarian approach to judging whether a proposed set of experiment is, or is not, ethical. In other words, there is an attempt to weigh up the potential benefits of the work in terms of advancing scientific knowledge, or the clinical treatment of human and animal disease, which is set against the dis-benefits in terms of impact on the welfare of the animals that will be used in that research. However, it incorporates elements of a more rights-based approach, in that experiments involving the use of old world apes (chimpanzees, gorillas etc) are prohibited. At present, with the exception of cephalopods, the current legislation ignores invertebrates. However there is increasing evidence sentience may be more widely distributed than previously appreciated, especially amongst decapods (crabs and lobsters), so it would not be surprising if the legal definition of a protected species was widened in the future.

At a practical level William Russell and Rex Birch suggested (Russell & Burch 1959) that there are three important considerations when designing an experiment that might, potentially, use non-humans:

• Replacement – could the use of non-human animals be replaced either by the ethical use of human participants or by the use of a non-animal technique – perhaps based on cultured cells?
• Reduction – could the use of animals be minimised in such a way that the results would remain statistically valid?
• Refinement – could the experimental programme be modified in a way that eliminated, or at least minimised, any pain or distress, perhaps by using positive rewards (e.g. palatable food) rather than punishment (e.g. electric shock) to motivate performance in a particular test situation?

In the UK, these practical ideas have to be addressed before experimental work is approved in the context of a broader cost-benefit analysis. The proposal has then to be considered by an ethics committee which includes lay members before it receives approval from the relevant government department.

Key Takeaways

• There was an increasing realisation from the period 200 BCE to 1700 CE that the brain was critical for overt behaviour, cognition and emotion. The contributions of Galen, Ibn Sina and Descartes are of particular note.
• During the 17th – 19th centuries it became clear that there was a considerable degree of localisation of function within the nervous system. Older fluid-based notions of information flow within the nervous system were gradually replaced within an understanding that it depended on electrical and chemical phenomena.
• During the first 70 years of the 20th century the mechanisms underlying nerve impulse conduction and synaptic transmission were clarified. However, the strong influence of the positivist movement within psychology and ethology devalued the investigation of cognition and emotion.
• In the latter part of the 20th and early part of the 21st century,  there has been increasing integration of neuroscientific techniques into behavioural studies. During this period it was also accepted that aspects of cognition and emotion that cannot be directly observed are proper subjects for study in biological psychology.
• The investigation of any aspect of behaviour may involve the study of (i) causation and mechanisms, (ii) development, (iii) evolution and (iv) function or current utility. These are Tinbergen’s ‘four questions’.
• In the study of causation and development a mix of correlational and experimental strategies can be used. They each have their own advantages and pitfalls.
• Ethical considerations are important considerations in any study of biological psychology. They are based on the strong principle-based ethical code shared by all psychologists, and the specific principles of refinement, reduction and replacement.

Postscript: three basic concepts from biology

The first descriptions of cells were made in the middle of the seventeenth century by Antonie van Leewenhoek and Robert Hooke. Only in the middle of the nineteenth century was it accepted that all living organisms are made up from one or more cells as their basic organisational unit. In 1855 Rudolf Virchow proposed that all cells arise from pre-existing cells by cell division. Each cell contains the different types of organelles that allows that cell to function. Critical amongst these, at least in all multicellular organisms, is the nucleus , which contains the chromosomes made up of DNA which, in its detailed chemical structure, encodes all the information that the cell needs to reproduce. The cell also has mitochondria that provide the cell with energy and a membrane that bounds it, as well as many other types of organelle.

Cells are grouped into tissues, composed of one or more different cell types, and different tissues are combined together to form organs, such as heart, lungs and brain, formed of many different types of tissue.

Inheritance

When a cell divides, the daughter cell needs the necessary information to duplicate the functions of its parent. The plant breeding experiments of Gregor Mendel in the late 1800s, when combined with the detailed studies of Thomas Hunt Morgan on the ways in which chromosomes replicate during cell division in the early twentieth century, suggested that DNA, which made up much of their substance, must be the molecule that had that function. In the 1950s James Watson, Francis Crick, Rosalind Franklin and others showed that the detailed ordering of one of four nucleotide bases in the double helical chain that makes up DNA provided the code which could be translated into the ordering of amino acids in proteins. Proteins are fundamental to cell function – they function as enzymes, allowing simple chemical transformations to build a cell’s structure, generate energy and provide mechanisms that allow communication from one cell to another within complex organisms made of potentially billions of cells. Changes in a specific base within the DNA sequence are one form of mutation (so-called single nucleotide polymorphisms – SNPs) that can lead to a change in the structure and functioning of a protein. Larger scale mutations may involve the loss or duplication of parts of a chromosome and are often associated with more substantial changes in body structure, functioning or behaviour.

Evolution by natural selection

The idea that one type (or species) of animal can give rise to another as result of gradual change from one generation to another recurs in the writings of Islamic, Chinese and Greek philosophers, although some Greek writers – such as Plato and his pupil Aristotle – held the opposite view,  and held that the form of individual species was fixed and unchanging. But it was Charles Darwin who gave the first clear account of the role of natural selection in evolutionary change. His theory proposed three essential postulates:

• that individuals differ from one to another;
• that this variation may be inherited;
• and that some individuals, as results of this variation, leave greater numbers of offspring.

The consequence is that the characteristics of more successful individuals will become more common in the population. In this way a population, perhaps subject to different environmental pressures over the areas in which it is found, may gradually split into two, and evolve mechanisms that make cross-breeding less likely so as to preserve those inherited differences which adapt them to their differing environments.

Darwin’s ideas were very controversial and opposed by many public figures and religious leaders as well as by other scientists. Ironically, Virchow – who had been on the right side of the argument in relation to the way in which new cells arise by division  – was one of Darwin’s most vociferous opponents in Germany. He regarded Darwin’s ideas as an attack on the moral basis of society. Outstanding scientists can be right in one area, but hopelessly wrong in others!

Plan for the remainder of this textbook

The following chapters of this text cover the broad topic of biological psychology. They begin with an account of the structure of the brain and nervous system, and the functioning of the cellular units that make it up. The discussion then moves to the way in which the nervous system processes and interprets diverse types of sensory information, and the motor mechanisms that generate an observable behavioural output. In addition to a focus on the understanding of ‘normal’ behaviour, you will read about the extent to which clinical conditions, such as anxiety and depression, may be accompanied by specific changes in brain function and the way in which clinically useful drugs may affect both the function of individual neurones and larger scale brain circuits. Future editions of this book will also include chapters that discuss topics such as motivation, emotion and the neural mechanisms that underpin learning and memory.

References and further reading

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Bergström, A., McCarthy, S. A., Hui, R., Almarri, M. A., Ayub, Q., Danecek, P., Chen, Y., Felkel, S., Hallast, P., Kamm, J., Blanché, H., Deleuze, J.-F., Cann, H., Mallick, S., Reich, D., Sandhu, M. S., Skoglund, P., Scally, A., Xue, Y., … Tyler-Smith, C. (2020). Insights into human genetic variation and population history from 929 diverse genomes. Science , 367 (6484), eaay5012. https://doi.org/10.1126/science.aay5012

Berridge, K. C. (2019). Affective valence in the brain: Modules or modes? Nature Reviews Neuroscience , 20 (4), 225–234. https://doi.org/10.1038/s41583-019-0122-8

Brebner, L. S., Ziminski, J. J., Margetts-Smith, G., Sieburg, M. C., Reeve, H. M., Nowotny, T., Hirrlinger, J., Heintz, T. G., Lagnado, L., Kato, S., Kobayashi, K., Ramsey, L. A., Hall, C. N., Crombag, H. S., & Koya, E. (2020). The emergence of a stable neuronal ensemble from a wider pool of activated neurons in the dorsal medial prefrontal cortex during appetitive learning in mice. Journal of Neuroscience , 40 (2), 395–410. https://doi.org/10.1523/JNEUROSCI.1496-19.2019

Cook, M., & Mineka, S. (1990). Selective associations in the observational conditioning of fear in rhesus monkeys. Journal of Experimental Psychology. Animal Behavior Processes , 16 (4), 372–389.

Darwin, Charles. (1872). The expression of the emotions in animals and Man .

Descartes, R. (1998). Descartes: The world and other writings (S. Gaukroger, Ed.). Cambridge University Press. https://doi.org/10.1017/CBO9780511605727

Dickinson, A. (1980). Contemporary animal learning theory . Cambridge University Press.

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Garfinkel, S. N., & Critchley, H. D. (2016). Threat and the body: How the heart supports fear processing. Trends in Cognitive Sciences , 20 (1), 34–46. https://doi.org/10.1016/j.tics.2015.10.005

Goodall, J. (2017, January 20). Remembering my mentor: Robert Hinde. Jane Goodall’s Good for All News . https://news.janegoodall.org/2017/01/20/remembering-my-mentor-robert-hinde/

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The idea that mind and body are separate

hormone-producing

About the author

name: Professor Pete Clifton

institution: University of Sussex

Pete Clifton is Professor of Psychology at the University of Sussex. He was the founding Head of the School of Psychology, holding that position from June 2009 to July 2014. His research has focused on the different roles of the brain transmitter serotonin in motivation, especially feeding, and cognition. He is a Chartered Psychologist and Fellow of the British Psychological Society.

Introduction to Biological Psychology Copyright © 2023 by Professor Pete Clifton is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

Digital Object Identifier (DOI)

https://doi.org/10.20919/ZDGF9829/1

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Biopsychology Overview

Have you ever wondered why you react the way you do to certain situations? Or why some smells transport you to memories from long ago? The answers to these questions lie at the intersection of biology and psychology.

Biopsychology is the study of how our brain's biology influences our thoughts, emotions, and behaviors. It seeks to understand the relationship between the neural circuits, chemicals in our brain, and the experiences we face every day.

In this journey, we will delve deep into the wonders of the brain, from how emotions are formed to the role of hormones in our behavior. You'll have an appreciation for the organ inside your skull and a deeper understanding of yourself.

What is Biopsychology?

Imagine being handed a bunch of puzzle pieces but no guiding image. Each piece represents a snippet of your feelings, behaviors, and reactions. You try to fit them together, hoping to see the full picture, but it's challenging.

Biopsychology, in many ways, provides that guiding image. It offers a clearer image of how your brain's biology works with your psychological experiences.

Every emotion you've ever felt, every choice you've made, every song that’s stuck in your head are all born from the collaboration between parts of your brain.

Psychology seeks to understand behavior and mind. Biology focuses on the physical and chemical processes in our bodies. Biopsychology combines biology and psychology to help us better understand ourselves.

So, why should you care? Well, understanding biopsychology can offer insights into everyday questions.

Ever wondered why certain foods comfort you? Or why a particular song can make you cry? Behind those simple moments are complex interactions of neurotransmitters, hormones, and neural networks.

By understanding the reasons behind our behaviors, we can make better decisions, have stronger relationships, and boost our well-being.

But it’s not only about individual understanding. On a broader scale, biopsychology has tremendous implications in the medical world.

Biopsychology has helped us create treatments for mental health disorders. It has also paved the way for breakthroughs in neurology.

Remember, our brains aren't just spongy organs resting in our skulls. They're the centers of our experiences, the drivers of our behaviors, and the essence of who we are.

Structure and Functions of the Brain

Imagine your brain as a supercomputer. Just like a computer has hardware and software that work together to run programs, your brain has structures and functions that work together to shape your thoughts, emotions, and behaviors.

And while we often think of the brain as one big organ, it's actually made up of many different parts , each with its own unique job .

The largest part of your brain is the cerebrum . It’s like the CEO of a company, overseeing and controlling most of what you think and do. This part handles thinking, learning, problem-solving, and sensing.

The cerebrum has a left and right half , often called hemispheres . The two sides might look alike, but they often have different roles.

The left side of the brain handles language. The right side recognizes faces and spatial relationships.

Below the cerebrum lies the cerebellum , which you can think of as the conductor of an orchestra. It doesn’t make the music, but it ensures all parts play in harmony.

In your body, the cerebellum helps with coordination and balance. It’s the reason you can walk without tumbling over or reach out to grab something without missing.

Deeper inside, you'll find the brainstem . The brainstem controls many of the automatic functions, like breathing and heartbeat.

But it's not only about structure; it's about communication too. All these parts of the brain talk to each other using something called neural pathways .

Think of these like roads in a city that connect different neighborhoods or brain areas. The more you use a pathway, the stronger it becomes.

That's why practicing a new skill starts off feeling hard but becomes easier over time.

Every person’s brain is unique. It’s shaped by genetics, experiences, and even the choices you make. So while we all have the same basic parts, how they work together makes you distinctively you . And that’s the real magic.

Neurons and Neurotransmitters

Imagine the brain as a bustling city. In this city, messages need to travel fast, from one end to the other, making sure everything runs smoothly.

Instead of delivery trucks and courier services, your brain has neurons and neurotransmitters .

Neurons are like the dedicated postal workers of this city. They are specialized cells designed to send information throughout the brain and the rest of the body.

Picture a tree, with roots, a trunk, and branches. In a neuron, these parts are:

• the dendrites (like roots), which receive messages
• the axon (the trunk), which carries the message
• the axon terminals (the branches), that pass the message on

Every second, these neurons send and receive messages that allow you to think, feel, and act.

Now, you might wonder, how do these messages jump from one neuron to the next?

That's where neurotransmitters come into play. Think of them as the delivered letters or packages.

These are special chemicals that transfer the message across a tiny space called the synapse . Like different letters convey different news or emotions, different neurotransmitters have different effects.

For instance, serotonin is a neurotransmitter often linked to feelings of happiness and well-being. And dopamine is about pleasure and reward.

It's fascinating, isn't it? You see a delicious piece of chocolate cake, and suddenly crave a bite. Behind that simple desire is an intricate dance of neurons firing and neurotransmitters passing messages. All that action leads to the urge to indulge.

But it's not only about cravings. The balance (or imbalance) of these neurotransmitters is important.

Ever felt the rush of happiness after a good workout? That's a balanced release of endorphins , another type of neurotransmitter. Imagine if you always felt that same rush. You wouldn't be able to calm down!

These imbalances can mean there is too much or too little of a neurotransmitter, or too strong or too weak communication between them. Imbalances in neurotransmitters are linked to various disorders, like depression or anxiety.

Brain Waves and Consciousness

Picture this: you’re at the beach, watching the waves crash on the shore. Some waves are large and powerful, while others are small and gentle.

Within the depths of your brain, there are waves too, not of water, but of electrical activity. These are brain waves , and they give insights into your state of consciousness.

When you're wide awake, alert, and focused on a task, like solving a puzzle or reading this article, your brain is buzzing with activity.

During these moments, it produces beta waves . Think of them as the fast, short waves on the beach when the wind picks up. They're a sign of mental engagement.

On the other end of the spectrum, when you're in the deepest phase of sleep , your brain emits delta waves .

These waves are slow and long, resembling the gentle, rolling waves during a calm morning at the beach. This is when your body is resting, healing, and re-energizing for the next day.

There are also states between. Ever been lost in thought, daydreaming, or meditating? During these relaxed, reflective moments, your brain is likely producing alpha waves .

And as you start to drift into sleep or as you’re waking up, you're in the realm of theta waves , a space of light sleep and deep relaxation.

By studying brain waves, scientists can learn a lot about our mental and emotional states. For example, disruptions in brain wave patterns can show certain disorders or conditions.

The Emotional Brain

Have you ever been surprised by a sudden rush of emotion, perhaps from a forgotten song on the radio or the scent of a familiar perfume?

Emotions are a universal part of the human experience, yet their origin and purpose have mystified us for centuries.

Biopsychology tells us that your feelings aren't momentary sensations. They are actually physical processes rooted in the brain .

At the heart of our emotional world lies a group of structures called the limbic system . Picture it as the emotional command center of your brain.

One key player here is the amygdala , a tiny almond-shaped structure. Think of the amygdala as the emotional security guard. It’s quick to judge if something is a threat or a reward, causing you to feel fear, joy, or other emotions.

Then there's the hippocampus , another vital member of the team. Its role is like a librarian who archives your emotional memories.

Ever felt nostalgic about a childhood spot or a person from the past? Thank the hippocampus for storing those emotional memories.

The hypothalamus , another part of the limbic system, plays a big role in guiding our actions. It's like the control room, sending signals to the rest of the body. It gets you ready to take action, whether that’s hugging a loved one or running from danger.

Of course, emotions aren't solely the result of these brain structures. They're also tied to hormones and neurotransmitters .

For instance, when you're feeling that excited sensation of being in love, there's a good chance the hormone oxytocin is at play.

Hormones and Behavior

You've probably heard the phrase, "It's just my hormones acting up!"

Hormones often play an underrated role in influencing our behaviors and emotions. They show up as mood swings during puberty, cravings during a period, or even the 'butterflies in your stomach' feeling during a first date.

Hormones are chemical messengers produced by glands in the endocrine system . They travel through our bloodstream to deliver important messages to different parts of the body.

Take cortisol , for example. This hormone is like the alarm bell that alerts the body when there's a stressful situation. It prepares you for the 'fight or flight' response.

Cortisol floods your body when you're nervous about giving a presentation or an upcoming event. This lets you be alert and face the challenge, but it also creates the signs of anxiety.

Then there’s testosterone , often linked with aggressive behavior. While it's primarily known as a male hormone, both genders produce it, but in different amounts.

Higher levels of testosterone can make someone more competitive or take more risks. Think about the adrenaline rush you get during an intense game or competition. That surge of daring? Testosterone plays a role.

On the softer side, we have estrogen , associated with nurturing and bonding behaviors. This hormone relates to maternal instincts and the emotional shifts during a menstrual cycle.

But it’s essential to remember: hormones don't work in isolation. They’re part of a complex interplay with our environment, experiences, and genetics. While they guide and influence, they don't dictate.

For instance, not everyone with high testosterone will be aggressive. And not all maternal feelings can be pinned solely on estrogen.

Knowing this can help us recognize when our invisible puppeteers are at work and choose how to respond. After all, while hormones might set the stage and offer a script, we still have the power to decide how to play our roles.

Genetics and Behavior

When you look in the mirror, do you ever wonder why you have your grandmother's nose or your father's eye color? It's because of those tiny instructions passed from generation to generation called genes .

But what if I told you that these genes don't only influence your appearance? They also influence your behaviors, personality, and even certain emotions .

Genes are the original set of instructions for building and operating the human body. They are kind of like the first draft of a detailed novel.

Everyone's book has a different story, thanks to the combination of genes inherited from our parents.

Now, one of the most discussed concepts in biopsychology is the nature vs. nurture debate .

Does our behavior come from our genetics (nature), or our environment and experiences (nurture)?

The question started with ancient philosophers. Plato , for instance, believed that certain ideas and characteristics were present at birth. Aristotle leaned more towards the idea that our mind is a blank slate, or tabula rasa , and that we're influenced by our experiences.

As the understanding of genetics increased in the 20th century, the debate intensified. Researchers began to realize that human development isn't as black and white as picking a side in this debate. Instead, it's an interplay of both genetic factors and environmental influences.

For example, while certain traits like eye color are almost entirely determined by genes, other attributes like personality or intelligence are influenced by a mix of both genetic and environmental factors.

Ever heard of monozygotic twins? They are identical twins with nearly the same genetic code. Research shows that even when these twins are raised apart, they often share similar personalities and interests.

But it's not all written in stone. Take the gene associated with the neurotransmitter serotonin , often linked to mood.

Certain amounts of serotonin can increase the risk of depression. But having that amount doesn't mean the person will be depressed. Environmental factors, like supportive relationships or coping strategies, can help balance genetic predispositions.

Simply put, both genes and environment influence who a person becomes. A child might inherit a love for music from a parent, but without exposure or encouragement, that built-in passion might never blossom.

Learning and Memory

Think back to your first bicycle ride. At first, you were probably afraid, but the fear turned to excitement when you found your balance. Fast forward, and riding a bike now feels like second nature. This transformation from uncertainty to mastery is due to the brain's ability to learn and remember.

Learning is the process by which we get new knowledge or skills. Your brain learns by forging and strengthening connections between neurons. These connections, called synapses , are like highways that ease the flow of information.

Now, onto memory. Memory ensures that what's learned isn't forgotten. It allows you to tap into past experiences and knowledge.

This storage system isn't one-size-fits-all; there are different types of memories stored in distinct parts of the brain.

Ever touched a hot pot and immediately pulled away? That's procedural memory at play, responsible for skills and habits. It lives in the basal ganglia and the cerebellum , ensuring you don't have to relearn everything from scratch each day.

Then there's declarative memory , which holds facts and events. Remembering your best friend's birthday or the capital of France? That's the work of the hippocampus and surrounding structures that catalogue this information for you.

But, memory isn't infallible. Ever walked into a room and forgot why? Or struggled to recall a word on the tip of your tongue? Memory glitches are natural. They are influenced by various factors like stress, lack of sleep, or even age.

You can't have learning without memory. Memory is essential to every task we do. But sometimes, we don't need to remember how to do something to do it. Like, we don't need to remember how to ride a bike, we just do it.

Senses and Perception

Close your eyes for a moment. Now, listen to the soft hums around you, feel the texture of the device in your hand, or breathe in and notice what you can smell.

These sensations are the basis of your experience. Without them, your connection to the world would be incredibly different. Your senses gather data from the environment. And your perception translates that data into meaningful stories.

Let's start with vision , our dominant sense. It begins in the eyes, where the retina's photoreceptor cells detect light. But seeing isn't only about recognizing brightness and color. It's also about understanding depth, movement, and shapes.

Ever wondered why a flat movie screen can depict such a vivid 3D world? It’s because your brain is a master at interpreting visual cues, turning simple light patterns into complex narratives.

Then there’s hearing , where waves of air pressure, or what we refer to as sound waves, vibrate the eardrum. These vibrations travel to the inner ear, getting translated into electrical signals.

Whether it's the soft strumming of a guitar or the chaos of a busy street, your ears and brain work together to make sense of these auditory patterns.

Next, consider touch . The skin, the body's largest organ, is peppered with receptors sensitive to pressure, temperature, and even pain.

Ever felt the prickly sensation of a foot that's 'fallen asleep'? That's your body’s network of touch sensors sending confused signals because of restricted blood flow.

Smell and taste , or olfaction and gustation , are the more intimate senses. They work closely, influencing each other. That's why food tastes bland when you have a stuffy nose.

The olfactory sense detects chemicals in the air that allow you to enjoy a fragrant flower. The gustatory sense detects chemicals in our food so we can enjoy a savory meal.

Yet, perception isn't merely a passive process. Past experiences, beliefs, and even mood can shape how you interpret sensory data.

That's why a song can sound sad to one person but uplifting to another, or why the same dish can evoke different memories for different people.

Stress and the Brain

Imagine being aboard a ship navigating turbulent waters. Waves crash, thunder roars, and the vessel sways, testing its resilience.

Similarly, life often sends challenges our way, and the brain, like that ship, tries to steer us through. This response to life's pressures and threats is what we call stress .

At its core, stress is a survival mechanism. Remember the last time you narrowly avoided an accident? Perhaps you braked just in time to prevent a collision, or swiftly sidestepped a falling object.

That heightened awareness and pulse is your brain's fight-or-flight response in action. The response is thanks to the amygdala , which sounds the alarm , and the hypothalamus , which kick-starts the reaction.

In the short term, stress can be beneficial. It sharpens focus, boosts energy, and prepares you for immediate action.

But prolonged exposure to stress? That's where problems begin. Chronic stress is like a ship stuck in stormy waters, straining its structure and causing wear and tear.

Chronic stress affects the brain in many ways. It can shrink the prefrontal cortex , which handles self-control, decision-making, and emotions. It enlarges the amygdala, increasing the risk of anxiety and emotional disorders.

Additionally, too much of the stress hormone cortisol can impair memory and concentration.

Beyond the brain, stress causes problems in the body. It can impact sleep patterns, weaken the immune system, and increase blood pressure. One system gets affected, and then another, and another, creating a chain reaction of health issues.

But here's the silver lining: just as the brain is vulnerable to stress, it's also resilient. You can counteract the effects of stress with mindfulness meditation , deep breathing exercises, and physical activity.

The Future of Biopsychology

Now you can see how vast and intricate the interplay between the brain and behavior is. But as with any scientific attempt, the more answers we uncover, the more questions arise.

So, what's next? What awaits on the horizon of biopsychological exploration?

Imagine a world where we can see the exact genetic markers linked to specific behaviors or psychological disorders. With advancements in genomic mapping and gene-editing technologies like CRISPR , this might soon be a reality.

Personalized treatments based on an individual's genes could revolutionize mental health care. Right now, we have a one-size-fits-all approach, but it doesn't actually work for everyone.

Then there's the promise of neuroimaging . As these techniques get better, we'll get better at understanding the brain.

Imagine being able to watch neural connections form during the learning process. Or observe the real-time impact of stress on brain structures. This could positively change how we approach education, therapy, and even professional training.

Brain-computer interfaces (BCIs) present another exciting opportunity. These tools ease direct communication between the brain and external devices. BCIs could help people with motor disabilities learn how to walk again. They could even teach people how to think critically.

Yet, with such progress comes important questions. If we can change genes linked to undesirable traits, where do we draw the line? What is "normal" or "acceptable" behavior?

We also have to ask questions about privacy, autonomy, and human identity.

The field of biopsychology has many innovations to offer. But it also requires responsibility for care and compassion. By staying informed and engaged, you, as part of society, can influence the direction this ship sails.

Stepping into the world of biopsychology is like opening a door to a vast, fascinating universe. It's where the magic of the mind meets the logic of biology.

From understanding how we think, feel, and act, to unraveling the mysteries of memory, emotions, and behavior, this field offers answers to some of life's biggest questions.

But as with any journey, the deeper we go, the more we realize there's so much more to explore. The future of biopsychology is full of possibilities. With every discovery, we get one step closer to understanding ourselves better.

Remember, this isn't just science for the experts. It's about you, me, and everyone around us. By learning about our brains and how they shape our lives, we can make better choices, be more compassionate, and appreciate the wonder that is human existence.

Related posts:

• Synaptic Cleft (Definition + Function)
• Hypophyseal Portal System
• Axon Terminal (Location + Function of the Brain)
• Hypothalamic Pituitary Adrenal Axis (HPA)
• Biological Psychologist Career (Salary + Duties + Interviews)

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Psychological Foundations

The Biological Domain

Learning objectives.

• Describe the basic interests and applications of biopsychology and evolutionary psychology

Biopsychology—also known as biological psychology or psychobiology—is the application of the principles of biology to the study of mental processes and behavior. As the name suggests, biopsychology explores how our biology influences our behavior. While biological psychology is a broad field, many biological psychologists want to understand how the structure and function of the nervous system is related to behavior. The fields of behavioral neuroscience, cognitive neuroscience, and neuropsychology are all subfields of biological psychology.

The research interests of biological psychologists span a number of domains, including but not limited to, sensory and motor systems, sleep, drug use and abuse, ingestive behavior, reproductive behavior, neurodevelopment, plasticity of the nervous system, and biological correlates of psychological disorders. Given the broad areas of interest falling under the purview of biological psychology, it will probably come as no surprise that individuals from all sorts of backgrounds are involved in this research, including biologists, medical professionals, physiologists, and chemists. This interdisciplinary approach is often referred to as neuroscience, of which biological psychology is a component (Carlson, 2013).

Evolutionary Psychology

While biopsychology typically focuses on the immediate causes of behavior based in the physiology of a human or other animal, evolutionary psychology seeks to study the ultimate biological causes of behavior. Just as genetic traits have evolved and adapted over time, psychological traits can also evolve and be determined through natural selection . Evolutionary psychologists study the extent that a behavior is impacted by genetics. The study of behavior in the context of evolution has its origins with Charles Darwin, the co-discoverer of the theory of evolution by natural selection. Darwin was well aware that behaviors should be adaptive and wrote books titled, The Descent of Man (1871) and The Expression of the Emotions in Man and Animals (1872), to explore this field.

Evolutionary psychology is based on the hypothesis that, just like hearts, lungs, livers, kidneys, and immune systems, cognition has functional structure that has a genetic basis, and therefore has evolved by natural selection. They seek to understand psychological mechanisms by understanding the survival and reproductive functions they might have served over the course of evolutionary history. These might include abilities to infer others’ emotions, discern kin from non-kin, identify and prefer healthier mates, cooperate with others and follow leaders. Consistent with the theory of natural selection, evolutionary psychology sees humans as often in conflict with others, including mates and relatives. For instance, a mother may wish to wean her offspring from breastfeeding earlier than does her infant, which frees up the mother to invest in additional offspring.

Evolutionary psychology, and specifically, the evolutionary psychology of humans, has enjoyed a resurgence in recent decades. To be subject to evolution by natural selection, a behavior must have a significant genetic cause. In general, we expect all human cultures to express a behavior if it is caused genetically, since the genetic differences among human groups are small. The approach taken by most evolutionary psychologists is to predict the outcome of a behavior in a particular situation based on evolutionary theory and then to make observations, or conduct experiments, to determine whether the results match the theory.

There are many areas of human behavior for which evolution can make predictions. Examples include memory, mate choice, relationships between kin, friendship and cooperation, parenting, social organization, and status (Confer et al., 2010).

Evolutionary psychologists have had success in finding experimental correspondence between observations and expectations. In one example, in a study of mate preference differences between men and women that spanned 37 cultures, Buss (1989) found that women valued earning potential factors greater than men, and men valued potential reproductive factors (youth and attractiveness) greater than women in their prospective mates. In general, the predictions were in line with the predictions of evolution, although there were deviations in some cultures.

Sensation and Perception

Scientists interested in both physiological aspects of sensory systems as well as in the psychological experience of sensory information work within the area of sensation and perception . As such, sensation and perception research is also quite interdisciplinary. Imagine walking between buildings as you move from one class to another. You are inundated with sights, sounds, touch sensations, and smells. You also experience the temperature of the air around you and maintain your balance as you make your way. These are all factors of interest to someone working in the domain of sensation and perception.

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• Evolutionary psychology. Provided by : Wikipedia. Located at : https://en.wikipedia.org/wiki/Evolutionary_psychology . License : CC BY-SA: Attribution-ShareAlike

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• Contemporary Psychology. Authored by : OpenStax College. Located at : https://openstax.org/books/psychology-2e/pages/1-3-contemporary-psychology . License : CC BY: Attribution . License Terms : Download for free at https://openstax.org/books/psychology-2e/pages/1-introduction
• Biopsychology information. Provided by : Boundless. Located at : https://courses.lumenlearning.com/boundless-psychology/ . License : CC BY-SA: Attribution-ShareAlike

study of how biology influences behavior

discipline that studies how universal patterns of behavior and cognitive processes have evolved over time as a result of natural selection

a process by which heritable traits conferring survival and reproductive advantage to individuals tend to be passed on to succeeding generations and become more frequent in a population

General Psychology Copyright © by OpenStax and Lumen Learning is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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Biological Basis of Behavior

The biological basis of behavior is an important field of study in psychology that explores the ways in which biological factors impact behavior. This includes investigating the roles that genetics, hormones, and the nervous system play in shaping an individual’s behavior.

One area of research within the biological basis of behavior is genetics. Studies have shown that certain genetic variations can influence an individual’s behavior, such as their risk for developing certain mental health disorders. For example, research has identified specific genetic mutations associated with an increased risk for schizophrenia.

Another important factor in the biological basis of behavior is hormones. Hormones are chemical messengers that are released by various glands throughout the body and can have significant effects on behavior. For example, the hormone testosterone is associated with aggression and dominance in both males and females.

The nervous system is also a key factor in the biological basis of behavior. This includes both the central nervous system, which consists of the brain and spinal cord, and the peripheral nervous system, which includes all the nerves outside of the brain and spinal cord. Research has shown that different regions of the brain are associated with specific behaviors, such as the amygdala’s role in fear and the prefrontal cortex’s role in decision-making.

Understanding the biological basis of behavior can have significant implications for mental health treatment and prevention. For example, identifying genetic markers associated with certain mental health disorders can help identify individuals at risk and lead to earlier interventions. Similarly, understanding how hormones and neurotransmitters impact behavior can inform the development of new treatments for mental health disorders.

In conclusion, the biological basis of behavior is a complex and fascinating field of study that sheds light on how biological factors contribute to an individual’s behavior. By exploring the interplay between genetics, hormones, and the nervous system, researchers can gain a better understanding of the underlying causes of mental health disorders and develop more effective treatments.

Biological Basis of Behavior Faculty

Biological basis of behavior labs, cognitive neuroscience of creativity laboratory, program areas:, gene environment interplay across the lifespan, associated centers:, laboratory of developmental neuroscience, cognition, affect, and temperament lab, laboratory for anxiety & depression research, brain injury & plasticity lab.

Biological psychology

Biological psychology, of biopsychology, is the application of the principles of biology to the study of mental processes and behavior, that is the study of psychology in terms of bodily mechanisms. The view that psychological processes have biological (or physiological) correlates, is the basic assumption of the whole field of biological psychology. Through a variety of research methods, psychologists in this field hope to uncover information that enriches human understanding of their own mental processes, as well as providing valuable data that enable those in medical fields to better treat patients with a variety of disorders, both physical and mental .

Biopsychology has been a prominent field of psychology from the start in Europe and North America and remains a major area of research and instruction in many countries. In the last two centuries, biopsychology has found new ways to answer old questions, has tackled important new questions, and has abandoned some problems as poorly defined. Carefully designed behavioral experiments and innovative biomedical techniques have been essential to its progress.

• 3 Contemporary biopsychology links psychology and biology
• 4.1 Disabling or decreasing neural function
• 4.2 Enhancing neural function
• 4.3 Measuring neural activity
• 5 Topic areas
• 6 Professional organizations and journals
• 8 References
• 9 External links

The current scope of biological psychology includes the following themes: Evolution of brain and behavior; development of the nervous system and behavior over the life span; psychopharmacology; sensory and perceptual processes; control and coordination of movement and actions; control of behavioral states ( motivation ), including sex and reproductive behavior, and regulation of internal states; biological rhythms and sleep; emotions and mental disorders ; neural mechanisms of learning and memory , language and cognition ; and recovery of function after damage to the nervous system . Developing from biological psychology and overlapping with parts of it are such fields as behavior genetics as well as hormones and behavior. Through all these methods, biological psychology is a hopeful domain, one that has much to offer in terms of improving the quality of life of the healthy as well as those suffering from disorders.

Synonyms to Biological Psychology include Biopsychology, Behavioral Neuroscience, and Psychobiology. [1] Physiological psychology is another term often used synonymously with biological psychology, though some authors would make physiological psychology a subfield of biological psychology, with an appropriately more narrow definition. The focus of study of physiological psychology is the neural mechanisms of perception and behavior through direct manipulation of the brains of nonhuman animal subjects in controlled experiments. [2]

The history of biological psychology is a major part of the history of modern scientific psychology . The study of biological psychology can be dated back to Avicenna (980-1037 C.E. ), a physician who in The Canon of Medicine, recognized physiological psychology in the treatment of illnesses involving emotions , and developed a system for associating changes in the pulse rate with inner feelings, which is seen as an anticipation of the word association test. [3] Avicenna also gave psychological explanations for certain somatic illnesses, and he always linked the physical and psychological illnesses together. He explained that "humidity" inside the head can contribute to mood disorders, and he recognized that this occurs when the amount of "breath" changes: Happiness increases the breath, which leads to increased moisture inside the brain , but if this moisture goes beyond its limits, the brain would lose control over its rationality and lead to mental disorders. [4]

Biological psychology as a scientific discipline later emerged from a variety of scientific and philosophical traditions in the eighteenth and nineteenth centuries. In philosophy, the first issues is how to approach what is known as the " mind-body problem ," namely the explanation of the relationship, if any, that obtains between minds , or mental processes, and bodily states or processes. Dualism is a family of views about the relationship between mind and physical matter. It begins with the claim that mental phenomena are, in some respects, non-physical. In Western Philosophy, some of the earliest discussions of dualist ideas are in the writings of Plato and Aristotle . Each of these maintained, but for different reasons, that human " intelligence " (a faculty of the mind or soul ) could not be identified with, or explained in terms of, his physical body. [5] However, the best-known version of dualism is due to René Descartes (expressed in his 1641, Meditations on First Philosophy ), and holds that the mind is a non-extended, non-physical substance. [6] Descartes was the first to clearly identify the mind with consciousness and self-awareness, and to distinguish this from the brain , which was the seat of intelligence.

The question then, is how do these separate and entirely different aspects of living beings, the mind and the body, relate? Some, like Descartes, proposed physical models to explain animal and human behavior. Descartes, for example, suggested that the pineal gland , a midline unpaired structure in the brain of many organisms, was the point of contact between mind and body. Descartes also elaborated on a theory in which the pneumatics of bodily fluids could explain reflexes and other motor behavior. This theory was inspired by moving statues in a garden in Paris. [7]

Other philosophers also helped to give birth to psychology, also relating its subject matter to biology. This view, that psychological processes have biological (or physiological) correlates, is the basic assumption of the whole field of biological psychology. One of the earliest textbooks in the new field, The Principles of Psychology by William James (1890), argues that the scientific study of psychology should be grounded in an understanding of biology:

Bodily experiences, therefore, and more particularly brain-experiences, must take a place amongst those conditions of the mental life of which Psychology need take account. The spiritualist and the associationist must both be "cerebralists," to the extent at least of admitting that certain peculiarities in the way of working of their own favorite principles are explicable only by the fact that the brain laws are a codeterminant of their result. Our first conclusion, then, is that a certain amount of brain-physiology must be presupposed or included in Psychology. [8]

William James, like many early psychologists , had considerable training in physiology . The emergence of both psychology and biological psychology as legitimate sciences can be traced from the emergence of physiology from anatomy , particularly neuroanatomy. Physiologists conducted experiments on living organisms, a practice that was distrusted by the dominant anatomists of the eighteenth and nineteenth centuries. [9] The influential work of Claude Bernard, Charles Bell, and William Harvey helped to convince the scientific community that reliable data could be obtained from living subjects.

The term "psychobiology" has been used in a variety of contexts, but was likely first used in its modern sense by Knight Dunlap in his book, An Outline of Psychobiology (1914) . [10] Although a "forgotten man" of American psychology, Dunlap also founded the journal Psychobiology . In the announcement of that journal, Dunlap writes that the journal will publish research "…bearing on the interconnection of mental and physiological functions," which describes the field of biological psychology even in its modern sense. [10]

Contemporary biopsychology links psychology and biology

For many decades, biopsychology or psychobiology has been a site of exchange of concepts , information , and techniques between psychology and the biological sciences . In many cases, humans may serve as experimental subjects in biological psychology experiments; however, a great deal of the experimental literature in biological psychology comes from the study of non-human species, most frequently rats , mice , and monkeys . As a result, a critical assumption in biological psychology is that organisms share biological and behavioral similarities, enough to permit extrapolations across species. This allies biological psychology closely with comparative psychology, evolutionary psychology, and evolutionary biology. Biological psychology also has paradigmatic and methodological similarities to neuropsychology, which relies heavily on the study of the behavior of humans with nervous system dysfunction (a non-experimentally based biological manipulation).

A psychobiologist or biopsychologist may compare the imprinting behavior in goslings to the early attachment behavior in human infants and construct theory around these two phenomena. Biological psychologists may often be interested in measuring some biological variable, such as an anatomical, physiological, or genetic variable, in an attempt to relate it quantitatively or qualitatively to a psychological or behavioral variable, and thus, contribute to evidence based practice.

Unlike other subdivisions within biological psychology, the main focus of physiological psychological research is the development of theories that explain brain-behavior relationships rather than the development of research that has translational value. It is sometimes alternatively called "psychophysiology," and in recent years also "cognitive neuroscience." One example of physiological psychology research is the study of the role of the hippocampus in learning and memory . This can be achieved by surgical removal of the hippocampus from the rat brain followed by an assessment of memory tasks by that same rat. [11]

Research methods

The distinguishing characteristic of a biological psychology experiment is that either the independent variable of the experiment is biological, or some dependent variable is biological. In other words, the nervous system of the organism under study is permanently or temporarily altered, or some aspect of the nervous system is measured (usually to be related to a behavioral variable). For example, in one treatment, a group of mice may be shown a particular color whereas the other treatment may receive no such stimulation before being measured (the dependent variable). Most commonly, these manipulations and measurements concern non-human subjects.

Disabling or decreasing neural function

One set of experimental methods involves disabling or decreasing neural function.

Lesions is a classic method in which a brain-region of interest is enabled. Lesions can be placed with relatively high accuracy thanks to a variety of brain "atlases" which provide a map of brain regions in three-dimensional stereotactic coordinates. The method of electrolytic lesions involves the destruction of neural tissue by the use of electric run through. Chemical lesions destroy neural tissue by the infusion of a neurotoxin. Temporary lesions may be employed when neural tissue is temporarily disabled by cooling or by the use of anesthetics such as tetrodotoxin.

Transcranial magnetic stimulation is a comparatively new technique usually used with human subjects in which a magnetic coil applied to the scalp causes unsystematic electrical activity in nearby cortical neurons which can be experimentally analyzed as a functional lesion.

In this method a chemical receptor antagonist induces neural activity by interfering with neurotransmission. Antagonists can be delivered systemically (such as by intravenous injection) or locally (intracebrally) during a surgical procedure.

Enhancing neural function

Enhancing neural function is another research method in biopsychology.

This is a classic method in which neural activity is enhanced by application of a small electrical current (too small to cause significant cell death).

A chemical receptor agonist facilitates neural activity by enhancing or replacing endogenous neurotransmitters. Agonists can be delivered systemically (such as by intravenous injection) or locally (intracebrally) during a surgical procedure.

In some cases (for example, studies of motor cortex), this technique can be analyzed as having a stimulatory effect (rather than as a functional lesion).

Measuring neural activity

Some biopsychological techniques measure neural activity.

This is the measurement of the electrical activity of one neuron, often in the context of an ongoing behavioral (psychological) task.

This involves a bundle of fine electrodes to record the simultaneous activity of up to hundreds of neurons.

fMRI or functional magnetic resonance imaging is a technique frequently applied to human subjects, in which changes in cerebral blood flow can be detected in an MRI apparatus and are taken to indicate relative activity of larger scale brain regions (on the order of hundreds of thousands of neurons).

Electroencephalography (or EEG) (including the derivative technique of event-related potentials) is the method in which scalp electrodes monitor the average activity of neurons in the cortex (again, used most frequently with human subjects).

Functional neuroanatomy is the method in which the expression of some anatomical marker is taken to reflect neural activity. For example, the expression of "immediate early genes" is thought to be caused by vigorous neural activity. Likewise, the injection of 2-deoxyglucose prior to some behavioral task can be followed by anatomical localization of that chemical; it is taken up by neurons that are electrically active.

Topic areas

In general, biological psychologists study the same issues as academic psychologists, though limited by the need to use nonhuman species. As a result, the bulk of literature in biological psychology deals with mental processes and behaviors that are shared across mammalian species, such as: Sensation and perception ; Motivated behavior (hunger, thirst, sex); Control of movement; Learning and memory ; Sleep and biological rhythms; Emotions .

With increasing technical sophistication and with the development of more precise noninvasive methods that can be applied to human subjects, Biological psychologists are beginning to contribute to other classical topic areas of psychology, such as: Language ; Reasoning and decision making; Consciousness .

Biological psychology has also had a strong history of contributing to medical disorders including those that fall under the purview of clinical psychology and psychopathology , also known as abnormal psychology . Although animal models for all mental illnesses do not exist, the field has contributed important therapeutic data on a variety of conditions, including:

• Parkinson's Disease, a degenerative disorder of the central nervous system that often impairs the sufferer's motor skills and speech.
• Huntington's Disease, a rare inherited neurological disorder whose most obvious symptoms are abnormal body movements and a lack of coordination. It also affects a number of mental abilities and some aspects of personality.
• Alzheimer's Disease , a neurodegenerative disease that, in its most common form, is found in people over the age of 65 and is characterized by progressive cognitive deterioration, together with declining activities of daily living and by neuropsychiatric symptoms or behavioral changes.
• Clinical depression , a common psychiatric disorder, characterized by a persistent lowering of mood, loss of interest in usual activities and diminished ability to experience pleasure.
• Schizophrenia , a psychiatric diagnosis that describes a mental illness characterized by impairments in the perception or expression of reality, most commonly manifesting as auditory hallucinations, paranoid or bizarre delusions or disorganized speech and thinking in the context of significant social or occupational dysfunction.
• Autism , a brain development disorder that impairs social interaction and communication, and causes restricted and repetitive behavior, all starting before a child is three years old.
• Anxiety , a physiological state characterized by cognitive, somatic, emotional, and behavioral components. These components combine to create the feelings that are typically recognized as fear, apprehension, or worry.
• Drug abuse , including alcoholism .

Professional organizations and journals

In the past, physiological psychologists received much of their their training in psychology departments in major universities. Currently, physiological psychologists are also be trained in behavioral neuroscience or biological psychology programs that are affiliated with psychology departments, or in interdisciplinary neuroscience programs. Professional positions in Biopsychology are mainly in academic and research institutions. Training for most of these positions requires a doctorate. Each year, the National Research Council lists over one hundred research doctorate programs in neuroscience in the United States .

Division 6 of the American Psychological Association (APA) is the scholarly and professional organization related to Biopsychology. APA publishes the journals Behavioral Neuroscience and Journal of Comparative and Physiological Psychology . The European Brain and Behaviour Society publishes the journal Behavioural Brain Research and the Forum of European Neuroscience Societies publishes the Journal of Neuroscience .

• ↑ S. Marc Breedlove, Mark R. Rosenzweig, and Neil V. Watson, Biological Psychology: An Introduction to Behavioral and Cognitive Neuroscience (Sinauer Associates, 2007, ISBN 978-0878937059 ).
• ↑ J.P.J. Pinel, Biopsychology (Allyn and Bacon, 2004, ISBN 0205426514 ).
• ↑ Ibrahim B. Syed, "Islamic Medicine: 1000 years ahead of its times," Journal of the International Society for the History of Islamic Medicine 2 (2002): 2-9.
• ↑ Amber Haque, "Psychology from Islamic Perspective: Contributions of Early Muslim Scholars and Challenges to Contemporary Muslim Psychologists," Journal of Religion and Health 43(4) (2004): 357-377.
• ↑ Plato, Phaedo, E.A. Duke, W.F. Hicken, W.S.M. Nicoll, D.B. Robinson, and J.C.G (eds.), Strachan (London: Clarendon Press, 1995.)
• ↑ René Descartes, Discourse on Method and Meditations on First Philosophy (Hacket Publishing Company, 1998, ISBN 0872204219 ).
• ↑ Neil Carlson, Physiology of Behavior, 9th edition (Allyn and Bacon, 2007, ISBN 0205467245 ).
• ↑ William James, The Principles of Psychology, Vol. One (Dover Publications, Inc., 1950, ISBN 0486203816 ).
• ↑ Gordon Shepard, Foundations of the Neuron Doctrine (Oxford University Press, 1991, ISBN 0195064917 ).
• ↑ 10.0 10.1 Donald Dewsbury, "Psychobiology" American Psychologist 46 (1991): 198-205
• ↑ D.S. Olton, J.T. Becker, and G.E. Handelmann, "Hippocampus, space, and memory," Brain and Behavioral Science 2(1979): 313–365.

References ISBN links support NWE through referral fees

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• Bain, Alexander. Mind and Body: The Theories of their Relation . Adamant Media Corporation, 2005 (original 1873). Template:ASIN:B07DBQQY3X
• Boring, Edwin G. A History of Experimental Psychology, 2nd edition. Englewood Cliffs, NJ: Prentice Hall, 1950. ISBN 0133900398
• Breedlove, S. M., M.R. Rosenzweig, and N.V. Watson. Biological Psychology: An Introduction to Behavioral and Cognitive Neuroscience. Sinauer Associates, 2007. ISBN 978-0878937059
• Brennan, J.F. History and Systems of Psychology . Englewood Cliffs, NJ: Prentice-Hall, 1986. ISBN 0133922189
• Carlson, N. Physiology of Behavior. Allyn and Bacon, 2007. ISBN 0205467245
• Darwin, Charles Robert. On the Origins of the Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle of Life . Adamant Media Corporation, 2001 (original 1886). ISBN 978-1402171932
• Darwin, Charles Robert. The Expression of the Emotions in Men and Animals . Adamant Media Corporation, 2005 (original 1872). ISBN 978-1421260464
• Dennis, Wayne (ed.). Readings in the History of Psychology . Amberg Press, 2007. ISBN 978-1406748437
• Hebb, Donald. O. The Organization of Behavior: A Neuropsychological Theory . Lawrence Erlbaum, 2002. ISBN 0805843000
• Herrnstein, R. J. "On the law of effect." Journal of the Experimental Analysis of Behavior 13 (1970): 243-266.
• Hubel, D.H. & T.N. Wiesel. "Binocular interaction in striate cortex of kittens reared with artificial squint." Journal of Neuropsychology 28 (1965): 1041-1059.
• James, William. The Principles of Psychology, Vol. One. Dover Publications, Inc., 1950. ISBN 0486203816
• Kaas, J.H. "Plasticity of sensory and motor maps in adult animals." Annual Review of Neuroscience 14 (1991): 137-167.
• Lashley, K. S. "In search of the engram." Symposia of the Society for Experimental Biology 4 (1950): 454-482.
• Leahey, Th. H. A History of Modern Psychology . Englewood Cliffs, NJ: Prentice Hall, 2000. ISBN 0130175730
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• Pinel, John P.J. Biopsychology. Allyn and Bacon, 2005. ISBN 0205426514
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External links

All links retrieved October 31, 2023.

• Biological Psychology Links
• Biological psychology at The Psychology Wiki

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Biological Psychology

To understand the behavior of humans and non-human animals better, biological principles are applied to these behaviors. This field is known as biological psychology, a branch of psychology that is also referred to as behavioural neuroscience. Biological psychologists seek to examine the anaphysiological processes behind different behaviors, whether normal or abnormal.

This article is a part of the guide:

• Synaptic Transmission
• Types of Neurons
• Neural Pathways of Smell, Taste, and Touch
• Neural Transmission
• The Auditory System

Browse Full Outline

• 1 Biological Psychology
• 2.1 The Central Nervous System
• 2.2 Lobes of the Brain
• 2.3 Language and Lateralization
• 2.4 Biology of Learning and Memory
• 2.5 Brain Development
• 3.1 Neural Transmission
• 3.2 Synaptic Transmission
• 4.1 The Endocrine System
• 5.1 The Visual System
• 5.2 The Auditory System
• 5.3 Neural Pathways of Smell, Taste, and Touch
• 5.4 Biological Control of Movement
• 6.1 Wakefulness and Sleep
• 6.2 Eating and Drinking
• 6.3 Sexual Development and Human Behavior

Compared to most branches of psychology, behavioural neuroscience is a scientific discipline that emerged during the 19 th century. However, biological psychology is deeply rooted in various fields in both science and philosophy.

Several early scientists and philosophers have expressed their beliefs with regards to studying psychology in the grounds of biology. One of them is William James, who wrote “The Principles of Psychology”. In this book, he argued that the physiology of brain must be taken into account in the study of psychology at some degree. Rene Descartes, a philosopher, believed that the pineal gland is where the body and the mind meet. He also formed models and theories regarding the effect of bodily fluids’ pneumatics in human reflexes and motor behavior.

In Harlow’s Phineas Gage brain injury case study (1848), the results proved that the functional work of the brain has significant implications in terms of behavioural neuroscience.

The first use of the term “psychobiology” in the modern times was in the 1914 book “An Outline of Psychobiology” by Knight Dunlap. This book and a journal on psychobiology were worked on by Dunlap in order to publish research studies that have the interconnection of physiological and mental functions as their grounds. Many years later, Edward Wilson wrote and published “Sociobiology”, a book that connected psychology and evolution.

Areas of Study

Early biological psychologists or behavioural neuroscientists focused their research on the relationships between mental processes and behaviors amongst different nonhuman animals. In particular, the areas that have been studied include sensation and perception, emotion, learning and memory, movement and control, motivation, language, sleep, reasoning and consciousness. Biological psychology has had a long list of contributions in the comprehensive study of various medical disorders. The most notable ones include Alzheimer’s disease (progressive cognitive deterioration and behavioural changes), Parkinson’s disease (central nervous system disorder) and Huntington’s disease (neurogenetic disorder). Schizophrenia, clinical depression, mania, anxiety disorders, autism and drug abuse are also hot areas of study in behavioural neuroscience today.

Three Aspects

There are three aspects or ways in which the biological perspective is significant in the study psychology. One of these is Physiology, in which the mechanisms of the nervous system are studied in order to understand human behavior. Another is the Comparative Method that studies and compares the different species of animals. Lastly, Genetics, as the investigation of inheritance of traits and attributes may help understand human behavior.

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Classic Psychology Experiments

The history of psychology is filled with fascinating studies and classic psychology experiments that helped change the way we think about ourselves and human behavior. Sometimes the results of these experiments were so surprising they challenged conventional wisdom about the human mind and actions. In other cases, these experiments were also quite controversial.

Some of the most famous examples include Milgram's obedience experiment and Zimbardo's prison experiment. Explore some of these classic psychology experiments to learn more about some of the best-known research in psychology history.

Harlow’s Rhesus Monkey Experiments

In a series of controversial experiments conducted in the late 1950s and early 1960s, psychologist Harry Harlow demonstrated the powerful effects of love on normal development. By showing the devastating effects of deprivation on young rhesus monkeys , Harlow revealed the importance of love for healthy childhood development.

His experiments were often unethical and shockingly cruel, yet they uncovered fundamental truths that have heavily influenced our understanding of child development.

In one famous version of the experiments, infant monkeys were separated from their mothers immediately after birth and placed in an environment where they had access to either a wire monkey "mother" or a version of the faux-mother covered in a soft-terry cloth. While the wire mother provided food, the cloth mother provided only softness and comfort.

Harlow found that while the infant monkeys would go to the wire mother for food, they vastly preferred the company of the soft and comforting cloth mother. The study demonstrated that maternal bonds   were about much more than simply providing nourishment and that comfort and security played a major role in the formation of attachments .

Pavlov’s Classical Conditioning Experiments

The concept of classical conditioning is studied by every entry-level psychology student, so it may be surprising to learn that the man who first noted this phenomenon was not a psychologist at all. Pavlov was actually studying the digestive systems of dogs when he noticed that his subjects began to salivate whenever they saw his lab assistant.

What he soon discovered through his experiments was that certain responses (drooling) could be conditioned by associating a previously neutral stimulus (metronome or buzzer) with a stimulus that naturally and automatically triggers a response (food). Pavlov's experiments with dogs established classical conditioning.

The Asch Conformity Experiments

Researchers have long been interested in the degree to which people follow or rebel against social norms. During the 1950s, psychologist Solomon Asch conducted a series of experiments designed to demonstrate the powers of conformity in groups.  

The study revealed that people are surprisingly susceptible to going along with the group, even when they know the group is wrong.​ In Asch's studies, students were told that they were taking a vision test and were asked to identify which of three lines was the same length as a target line.

When asked alone, the students were highly accurate in their assessments. In other trials, confederate participants intentionally picked the incorrect line. As a result, many of the real participants gave the same answer as the other students, demonstrating how conformity could be both a powerful and subtle influence on human behavior.

Skinner's Operant Conditioning Experiments

Skinner studied how behavior can be reinforced to be repeated or weakened to be extinguished. He designed the Skinner Box where an animal, often a rodent, would be given a food pellet or an electric shock. A rat would learn that pressing a level delivered a food pellet. Or the rat would learn to press the lever in order to halt electric shocks.

Then, the animal may learn to associate a light or sound with being able to get the reward or halt negative stimuli by pressing the lever. Furthermore, he studied whether continuous, fixed ratio, fixed interval , variable ratio, and variable interval reinforcement led to faster response or learning.

Milgram’s Obedience Experiments

In Milgram's experiment , participants were asked to deliver electrical shocks to a "learner" whenever an incorrect answer was given. In reality, the learner was actually a confederate in the experiment who pretended to be shocked. The purpose of the experiment was to determine how far people were willing to go in order to obey the commands of an authority figure.

Milgram  found that 65% of participants were willing to deliver the maximum level of shocks   despite the fact that the learner seemed to be in serious distress or even unconscious.

Why This Experiment Is Notable

Milgram's experiment is one of the most controversial in psychology history. Many participants experienced considerable distress as a result of their participation and in many cases were never debriefed after the conclusion of the experiment. The experiment played a role in the development of ethical guidelines for the use of human participants in psychology experiments.

The Stanford Prison Experiment

Philip Zimbardo's famous experiment cast regular students in the roles of prisoners and prison guards. While the study was originally slated to last 2 weeks, it had to be halted after just 6 days because the guards became abusive and the prisoners began to show signs of extreme stress and anxiety.

Zimbardo's famous study was referred to after the abuses in Abu Ghraib came to light. Many experts believe that such group behaviors are heavily influenced by the power of the situation and the behavioral expectations placed on people cast in different roles.

It is worth noting criticisms of Zimbardo's experiment, however. While the general recollection of the experiment is that the guards became excessively abusive on their own as a natural response to their role, the reality is that they were explicitly instructed to mistreat the prisoners, potentially detracting from the conclusions of the study.

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Koren M. B.F. Skinner: The man who taught pigeons to play ping-pong and rats to pull levers . Smithsonian Magazine .

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Zimbardo PG. Philip G. Zimbardo on his career and the Stanford Prison Experiment's 40th anniversary. Interview by Scott Drury, Scott A. Hutchens, Duane E. Shuttlesworth, and Carole L. White. Hist Psychol. 2012;15(2):161-170. doi:10.1037/a0025884

Le texier T. Debunking the Stanford Prison Experiment. Am Psychol. 2019;74(7):823-839. doi:10.1037/amp0000401

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By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

7 Famous Psychology Experiments

Many famous experiments studying human behavior have impacted our fundamental understanding of psychology. Though some could not be repeated today due to breaches in ethical boundaries, that does not diminish the significance of those psychological studies. Some of these important findings include a greater awareness of depression and its symptoms, how people learn behaviors through the process of association and how individuals conform to a group.

Below, we take a look at seven famous psychological experiments that greatly influenced the field of psychology and our understanding of human behavior.

The Little Albert Experiment, 1920

A John’s Hopkins University professor, Dr. John B. Watson, and a graduate student wanted to test a learning process called classical conditioning. Classical conditioning involves learning involuntary or automatic behaviors by association, and Dr. Watson thought it formed the bedrock of human psychology.

A nine-month-old toddler, dubbed “Albert B,” was volunteered for Dr. Watson and Rosalie Rayner ‘s experiment. Albert played with white furry objects, and at first, the toddler displayed joy and affection. Over time, as he played with the objects, Dr. Watson would make a loud noise behind the child’s head to frighten him. After numerous trials, Albert was conditioned to be afraid when he saw white furry objects.

The study proved that humans could be conditioned to enjoy or fear something, which many psychologists believe could explain why people have irrational fears and how they may have developed early in life. This is a great example of experimental study psychology.

Stanford Prison Experiment, 1971

Stanford professor Philip Zimbardo wanted to learn how individuals conformed to societal roles. He wondered, for example, whether the tense relationship between prison guards and inmates in jails had more to do with the personalities of each or the environment.

During Zimbardo’s experiment , 24 male college students were assigned to be either a prisoner or a guard. The prisoners were held in a makeshift prison inside the basement of Stanford’s psychology department. They went through a standard booking process designed to take away their individuality and make them feel anonymous. Guards were given eight-hour shifts and tasked to treat the prisoners just like they would in real life.

Zimbardo found rather quickly that both the guards and prisoners fully adapted to their roles; in fact, he had to shut down the experiment after six days because it became too dangerous. Zimbardo even admitted he began thinking of himself as a police superintendent rather than a psychologist. The study confirmed that people will conform to the social roles they’re expected to play, especially overly stereotyped ones such as prison guards.

“We realized how ordinary people could be readily transformed from the good Dr. Jekyll to the evil Mr. Hyde,” Zimbardo wrote.

The Asch Conformity Study, 1951

Solomon Asch, a Polish-American social psychologist, was determined to see whether an individual would conform to a group’s decision, even if the individual knew it was incorrect. Conformity is defined by the American Psychological Association as the adjustment of a person’s opinions or thoughts so that they fall closer in line with those of other people or the normative standards of a social group or situation.

In his experiment , Asch selected 50 male college students to participate in a “vision test.” Individuals would have to determine which line on a card was longer. However, the individuals at the center of the experiment did not know that the other people taking the test were actors following scripts, and at times selected the wrong answer on purpose. Asch found that, on average over 12 trials, nearly one-third of the naive participants conformed with the incorrect majority, and only 25 percent never conformed to the incorrect majority. In the control group that featured only the participants and no actors, less than one percent of participants ever chose the wrong answer.

Asch’s experiment showed that people will conform to groups to fit in (normative influence) because of the belief that the group was better informed than the individual. This explains why some people change behaviors or beliefs when in a new group or social setting, even when it goes against past behaviors or beliefs.

The Bobo Doll Experiment, 1961, 1963

Stanford University professor Albert Bandura wanted to put the social learning theory into action. Social learning theory suggests that people can acquire new behaviors “through direct experience or by observing the behavior of others.” Using a Bobo doll , which is a blow-up toy in the shape of a life-size bowling pin, Bandura and his team tested whether children witnessing acts of aggression would copy them.

Bandura and two colleagues selected 36 boys and 36 girls between the ages of 3 and 6 from the Stanford University nursery and split them into three groups of 24. One group watched adults behaving aggressively toward the Bobo doll. In some cases, the adult subjects hit the doll with a hammer or threw it in the air. Another group was shown an adult playing with the Bobo doll in a non-aggressive manner, and the last group was not shown a model at all, just the Bobo doll.

After each session, children were taken to a room with toys and studied to see how their play patterns changed. In a room with aggressive toys (a mallet, dart guns, and a Bobo doll) and non-aggressive toys (a tea set, crayons, and plastic farm animals), Bandura and his colleagues observed that children who watched the aggressive adults were more likely to imitate the aggressive responses.

Unexpectedly, Bandura found that female children acted more physically aggressive after watching a male subject and more verbally aggressive after watching a female subject. The results of the study highlight how children learn behaviors from observing others.

The Learned Helplessness Experiment, 1965

Martin Seligman wanted to research a different angle related to Dr. Watson’s study of classical conditioning. In studying conditioning with dogs, Seligman made an astute observation : the subjects, which had already been conditioned to expect a light electric shock if they heard a bell, would sometimes give up after another negative outcome, rather than searching for the positive outcome.

Under normal circumstances, animals will always try to get away from negative outcomes. When Seligman tested his experiment on animals who hadn’t been previously conditioned, the animals attempted to find a positive outcome. Oppositely, the dogs who had been already conditioned to expect a negative response assumed there would be another negative response waiting for them, even in a different situation.

The conditioned dogs’ behavior became known as learned helplessness, the idea that some subjects won’t try to get out of a negative situation because past experiences have forced them to believe they are helpless. The study’s findings shed light on depression and its symptoms in humans.

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The Milgram Experiment, 1963

In the wake of the horrific atrocities carried out by Nazi Germany during World War II, Stanley Milgram wanted to test the levels of obedience to authority. The Yale University professor wanted to study if people would obey commands, even when it conflicted with the person’s conscience.

Participants of the condensed study , 40 males between the ages of 20 and 50, were split into learners and teachers. Though it seemed random, actors were always chosen as the learners, and unsuspecting participants were always the teachers. A learner was strapped to a chair with electrodes in one room while the experimenter äóñ another actor äóñ and a teacher went into another.

The teacher and learner went over a list of word pairs that the learner was told to memorize. When the learner incorrectly paired a set of words together, the teacher would shock the learner. The teacher believed the shocks ranged from mild all the way to life-threatening. In reality, the learner, who intentionally made mistakes, was not being shocked.

As the voltage of the shocks increased and the teachers became aware of the believed pain caused by them, some refused to continue the experiment. After prodding by the experimenter, 65 percent resumed. From the study, Milgram devised the agency theory , which suggests that people allow others to direct their actions because they believe the authority figure is qualified and will accept responsibility for the outcomes. Milgram’s findings help explain how people can make decisions against their own conscience, such as when participating in a war or genocide.

The Halo Effect Experiment, 1977

University of Michigan professors Richard Nisbett and Timothy Wilson were interested in following up a study from 50 years earlier on a concept known as the halo effect . In the 1920s, American psychologist Edward Thorndike researched a phenomenon in the U.S. military that showed cognitive bias. This is an error in how we think that affects how we perceive people and make judgements and decisions based on those perceptions.

In 1977, Nisbett and Wilson tested the halo effect using 118 college students (62 males, 56 females). Students were divided into two groups and were asked to evaluate a male Belgian teacher who spoke English with a heavy accent. Participants were shown one of two videotaped interviews with the teacher on a television monitor. The first interview showed the teacher interacting cordially with students, and the second interview showed the teacher behaving inhospitably. The subjects were then asked to rate the teacher’s physical appearance, mannerisms, and accent on an eight-point scale from appealing to irritating.

Nisbett and Wilson found that on physical appearance alone, 70 percent of the subjects rated the teacher as appealing when he was being respectful and irritating when he was cold. When the teacher was rude, 80 percent of the subjects rated his accent as irritating, as compared to nearly 50 percent when he was being kind.

The updated study on the halo effect shows that cognitive bias isn’t exclusive to a military environment. Cognitive bias can get in the way of making the correct decision, whether it’s during a job interview or deciding whether to buy a product that’s been endorsed by a celebrity we admire.

How Experiments Have Impacted Psychology Today

Contemporary psychologists have built on the findings of these studies to better understand human behaviors, mental illnesses, and the link between the mind and body. For their contributions to psychology, Watson, Bandura, Nisbett and Zimbardo were all awarded Gold Medals for Life Achievement from the American Psychological Foundation. Become part of the next generation of influential psychologists with King University’s online bachelor’s in psychology . Take advantage of King University’s flexible online schedule and complete the major coursework of your degree in as little as 16 months. Plus, as a psychology major, King University will prepare you for graduate school with original research on student projects as you pursue your goal of being a psychologist.

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From decades to days, biophysicists reveal DNA behavior in record time

by Delft University of Technology

Studying how single DNA molecules behave helps us to better understand genetic disorders and design better drugs. Until now, however, examining DNA molecules one-by-one was a slow process.

Biophysicists from Delft University of Technology and Leiden University developed a technique that speeds up screening of individual DNA molecules at least a thousand times. With this technology, they can measure millions of DNA molecules within a week instead of years to decades. The study is published in Science .

"DNA, RNA and proteins are the key players to regulate all processes in the cells of our body," Leiden Professor John van Noort explains.

"To understand the (mis-)functioning of these molecules, it is essential to uncover how their 3D structure depends on their sequence and for this it is necessary to measure them one molecule at a time. However, single-molecule measurements are laborious and slow, and the number of possible sequence variations is massive."

Now the team of scientists has developed an innovative tool, called SPARXS (Single-molecule Parallel Analysis for Rapid eXploration of Sequence space), that allows for studying millions of DNA molecules simultaneously.

"Traditional techniques that allow one sequence to be probed at a time usually take hours of measurement time per sequence. With SPARXS, we can measure millions of molecules within a day to a week. Without SPARXS, such a measurement would take several years to decades," says Delft Professor Chirlmin Joo.

"SPARXS enables us to study large sequence libraries, providing new insights into how the structure and function of DNA depend on sequence. Additionally, the technique can be used to quickly find the best sequence for applications ranging from nanotechnology to personalized medicine," Ph.D. Candidate Carolien Bastiaanssen adds.

Never combined before

To create their new SPARXS technique, the researchers combined two existing technologies that had never been paired before: single-molecule fluorescence and next-generation Illumina sequencing.

In the first technique, molecules are labeled with a fluorescent dye and visualized using a sensitive microscope. The latter technique reads out millions of DNA codes simultaneously.

Joo says, "It took a year to determine whether combining the two techniques is feasible, four more years to develop a working method, and two additional years to ensure accuracy and consistency in measurements while managing the vast amount of data generated."

"The real fun and interesting part started when we needed to interpret the data," first author Ivo Severins says.

"Since these experiments that combine single-molecule measurements with sequencing are completely new, we had no idea what results we would and could obtain. It required a lot of searching within the data to find correlations and patterns, and to determine the mechanisms that underly the patterns that we see."

Overcoming data processing challenges

Another challenge they had to overcome was handling the large amount of data, Van Noort adds, "We had to develop an automated and robust analysis pipeline. This was particularly challenging as single molecules are fragile and yield only a tiny amount of light, making the data inherently noisy.

"Furthermore, the resulting data do not directly provide insights into how the sequence affects the structure and dynamics of DNA, even for the relatively simple DNA structures that we studied. To really test our understanding, we set up a model that incorporates our knowledge of the DNA structure, and compared it with the experimental data."

More precise manipulation and understanding of DNA sequences will likely lead to advances in medical treatments, such as more effective gene therapies and personalized medicine. The researchers also foresee biotechnological innovations and overall a better understanding of biology at the molecular level.

Joo concludes, "We expect applications in genetic research , drug development, and biotechnology will begin to emerge within the next five to 10 years."

Journal information: Science

Provided by Delft University of Technology

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