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Natural Experiments

Last updated 22 Mar 2021

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Experiments look for the effect that manipulated variables (independent variables, or IVs) have on measured variables (dependent variables, or DVs), i.e. causal effects.

Natural experiments are studies where the experimenter cannot manipulate the IV, so the DV is simply measured and judged as the effect of an IV. For this reason, participants cannot be randomly allocated to experimental groups as they are already pre-set, making them quasi-experiments . For instance, an experiment might investigate the relative levels of aggression observed in boys and girls in a primary school (the experimenter cannot manipulate who belongs to the ‘boy’ and ‘girl’ groups).

Evaluation of natural experiments:

- The natural settings where such experiments take place mean that results will have high ecological validity (i.e. they should relate well to real life behaviour).

- Demand characteristics are often not a problem, unlike laboratory experiments (i.e. participants are less likely to adjust their natural behaviour according to their interpretation of the study’s purpose, as they might not know they are taking part in a study).

- Being unable to randomly allocate participants to conditions means that sample bias may be an issue (e.g. other extraneous variables that change with the pre-set IV group differences may confound the results, meaning a causal IV-DV effect is unlikely).

- Ethical issues such as lack of informed consent commonly arise, as deception is often required; debriefing, once the observation/experiment has ended, is necessary.

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Whilst oftentimes people tend to think of experiments occurring in laboratories and controlled settings, psychologists also consider real-world environments as opportunities to investigate phenomena. Behaviour changes depending on the setting, and investigating research areas in their natural settings can amplify the validity of the findings. Natural experiments offer researchers the opportunity to investigate human behaviour in everyday life. 

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Which of the following experiments does not involve the researcher manipulating the independent variable? 

True or false: Similar to lab experiments, natural experiments are conducted in controlled settings.

True or false: Confounding/ extraneous variables can be an issue in natural experiments. 

After Hurricane Katrina, researchers wanted to investigate how the natural disaster affected mental health. What type of experiment is likely to be conducted? 

Sampling bias can be an issue in natural experiments; this can influence the research's...

True or false: Ethical issues can be a potential concern for natural experiments. 

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Jump to a key chapter

• We are going to explore natural experiments used in psychological research.
• We will start by highlighting the natural experiment definition.
• We will then explore how natural experiments are used in psychology and cover natural experiment examples of research to demonstrate to help illustrate our points.
• Moving on, we will cover natural and field experiments to highlight the differences between the two types of investigations.
• And to finish, we will explore the natural experiment's advantages and disadvantages.

Natural Experiment Defintion

Natural experiments are essentially experiments that investigate naturally occurring phenomena. The natural experiment definition is a research procedure that occurs in the participant's natural setting that requires no manipulation by the researcher.

In experiments, changes in the independent variable (IV) are observed to identify if these changes affect the dependent variable (DV). However, in natural experiments, the researcher does not manipulate the IV. Instead, they observe the natural changes that occur.

Some examples of naturally occurring IVs are sex at birth, whether people have experienced a natural disaster, experienced a traumatic experience, or been diagnosed with a specific illness.

These examples show that it's next to impossible for the researcher to manipulate these.

Natural Experiment: Psychology

Why may researchers choose to use a natural experiment? As we have just discussed, sometimes researchers can't manipulate the IV. But, they may still wish to see how changes in the IV affect the DV, so use a natural experiment.

Sometimes a researcher can manipulate the IV, but it may be unethical or impractical to do so, so they conduct a natural experiment.

In natural experiments, the researcher can see how changes in the IV affect a DV, but unlike in lab experiments, the researcher has to identify how the IV is changing. In contrast, lab experiments pre-determine how the IV will be manipulated.

Natural Experiment: Examples

Natural experiments often take place in real-world settings. An example can be seen in examining the effect of female and male performance in an office environment and if gender plays a role in the retention of customers. Other examples include examining behaviours in schools, and the effect age has on behaviour.

Let's look at a hypothetical study that uses a natural experiment research method.

A research team was interested in investigating attitudes towards the community after experiencing a natural disaster.

The study collected data using interviews. The IV was naturally occurring as the researcher did not manipulate the IV; instead, they recruited participants who had recently experienced a natural disaster.

Natural Experiment vs Field Experiment

The table below summarises the key similarities and differences between natural experiments vs field experiments.

Natural Experiment: Advantages and Disadvantages

In the following section will present the natural experiment's advantages and disadvantages. We will discuss the new research possibilities, causal conclusions, rare opportunities, pre-existing sampling bias and ethical issues.

New Research Opportunities

Natural experiments provide opportunities for research that can't be done for ethical and practical reasons.

For example, it is impossible to manipulate a natural disaster or maternal deprivation on participants.

So, natural experiments are the only ethical way for researchers to investigate the causal relationship of the above topics. Thus, natural experiments open up practical research opportunities to study conditions that cannot be manipulated.

High Ecological Validity

Natural experiments have high ecological validity because natural experiments study real-world problems that occur naturally in real-life settings.

When research is found to use and apply real-life settings and techniques, it is considered to have high mundane realism.

And the advantage of this is that the results are more likely applicable and generalisable to real-life situations.

Rare Opportunities

There are scarce opportunities for researchers to conduct a natural experiment. Most natural events are ‘one-off’ situations. Because natural events are unique, the results have limited generalisability to similar situations.

In addition, it is next to impossible for researchers to replicate natural experiments; therefore, it is difficult to establish the reliability of findings.

Pre-Existing Sampling Bias

In natural experiments, pre-existing sampling bias can be a problem. In natural experiments, researchers cannot randomly assign participants to different conditions because naturally occurring events create them. Therefore, in natural experiments, participant differences may act as confounding variables .

As a result, sample bias in natural experiments can lead to low internal validity and generalisability of the research.

Ethical Issues

Although natural experiments are considered the only ethically acceptable method for studying conditions that can't be manipulated, ethical issues may still arise. Because natural experiments are often conducted after traumatic events, interviewing or observing people after the event could cause psychological harm to participants.

Researchers should prepare for potential ethical issues, such as psychological harm, usually dealt with by offering therapy. However, this can be pretty costly. And the ethical issue may lead participants to drop out of the research, which can also affect the quality of the research.

Natural Experiment - Key takeaways

The natural experiment definition is a research procedure that occurs in the participant's natural setting that requires no manipulation of the researcher.

The advantages of natural experiments are that they provide opportunities for research that researchers cannot do for ethical or practical reasons and have high ecological validity.

The disadvantages of natural experiments are reliability issues, pre-existing sample bias, and ethical issues, such as conducting a study after traumatic events may cause psychological distress.

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Frequently Asked Questions about Natural Experiment

What is a natural experiment?

The natural experiment definition is a research procedure that occurs in the participant's natural setting that requires no manipulation of the researcher. 

What is an example of natural experiment?

Beckett (2006) investigated the effects of deprivation on children’s IQ at age 11. They compared 128 Romanian children who UK families had adopted at various ages and 50 UK children who had been adopted before six months. They found that Romanian children who had been adopted before six months of age had similar IQs to the UK children; however, Romanian children adopted after six months of age had much worse scores. 

What are the characteristics of a natural experiment?

The characteristics of natural experiments are that they are carried out in a natural setting and the IV is not manipulated in this type of experiment. 

What are the advantages and disadvantages of natural experiments?

And the disadvantages of natural experiments are reliability issues, pre-existing sample bias, and ethical issues, such as conducting a study after traumatic events may cause psychological distress.

What are natural experiments in research?

Natural experiments in psychology research are often used when manipulating a variable is unethical or impractical.

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15 Famous Experiments and Case Studies in Psychology

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Dr. Chris Drew is the founder of the Helpful Professor. He holds a PhD in education and has published over 20 articles in scholarly journals. He is the former editor of the Journal of Learning Development in Higher Education. [Image Descriptor: Photo of Chris]

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Psychology has seen thousands upon thousands of research studies over the years. Most of these studies have helped shape our current understanding of human thoughts, behavior, and feelings.

The psychology case studies in this list are considered classic examples of psychological case studies and experiments, which are still being taught in introductory psychology courses up to this day.

Some studies, however, were downright shocking and controversial that you’d probably wonder why such studies were conducted back in the day. Imagine participating in an experiment for a small reward or extra class credit, only to be left scarred for life. These kinds of studies, however, paved the way for a more ethical approach to studying psychology and implementation of research standards such as the use of debriefing in psychology research .

Case Study vs. Experiment

Before we dive into the list of the most famous studies in psychology, let us first review the difference between case studies and experiments.

• It is an in-depth study and analysis of an individual, group, community, or phenomenon. The results of a case study cannot be applied to the whole population, but they can provide insights for further studies.
• It often uses qualitative research methods such as observations, surveys, and interviews.
• It is often conducted in real-life settings rather than in controlled environments.
• An experiment is a type of study done on a sample or group of random participants, the results of which can be generalized to the whole population.
• It often uses quantitative research methods that rely on numbers and statistics.
• It is conducted in controlled environments, wherein some things or situations are manipulated.

See Also: Experimental vs Observational Studies

Famous Experiments in Psychology

1. the marshmallow experiment.

Psychologist Walter Mischel conducted the marshmallow experiment at Stanford University in the 1960s to early 1970s. It was a simple test that aimed to define the connection between delayed gratification and success in life.

The instructions were fairly straightforward: children ages 4-6 were presented a piece of marshmallow on a table and they were told that they would receive a second piece if they could wait for 15 minutes without eating the first marshmallow.

About one-third of the 600 participants succeeded in delaying gratification to receive the second marshmallow. Mischel and his team followed up on these participants in the 1990s, learning that those who had the willpower to wait for a larger reward experienced more success in life in terms of SAT scores and other metrics.

This case study also supported self-control theory , a theory in criminology that holds that people with greater self-control are less likely to end up in trouble with the law!

The classic marshmallow experiment, however, was debunked in a 2018 replication study done by Tyler Watts and colleagues.

This more recent experiment had a larger group of participants (900) and a better representation of the general population when it comes to race and ethnicity. In this study, the researchers found out that the ability to wait for a second marshmallow does not depend on willpower alone but more so on the economic background and social status of the participants.

2. The Bystander Effect

In 1694, Kitty Genovese was murdered in the neighborhood of Kew Gardens, New York. It was told that there were up to 38 witnesses and onlookers in the vicinity of the crime scene, but nobody did anything to stop the murder or call for help.

Such tragedy was the catalyst that inspired social psychologists Bibb Latane and John Darley to formulate the phenomenon called bystander effect or bystander apathy .

Subsequent investigations showed that this story was exaggerated and inaccurate, as there were actually only about a dozen witnesses, at least two of whom called the police. But the case of Kitty Genovese led to various studies that aim to shed light on the bystander phenomenon.

Latane and Darley tested bystander intervention in an experimental study . Participants were asked to answer a questionnaire inside a room, and they would either be alone or with two other participants (who were actually actors or confederates in the study). Smoke would then come out from under the door. The reaction time of participants was tested — how long would it take them to report the smoke to the authorities or the experimenters?

The results showed that participants who were alone in the room reported the smoke faster than participants who were with two passive others. The study suggests that the more onlookers are present in an emergency situation, the less likely someone would step up to help, a social phenomenon now popularly called the bystander effect.

3. Asch Conformity Study

Have you ever made a decision against your better judgment just to fit in with your friends or family? The Asch Conformity Studies will help you understand this kind of situation better.

In this experiment, a group of participants were shown three numbered lines of different lengths and asked to identify the longest of them all. However, only one true participant was present in every group and the rest were actors, most of whom told the wrong answer.

Results showed that the participants went for the wrong answer, even though they knew which line was the longest one in the first place. When the participants were asked why they identified the wrong one, they said that they didn’t want to be branded as strange or peculiar.

This study goes to show that there are situations in life when people prefer fitting in than being right. It also tells that there is power in numbers — a group’s decision can overwhelm a person and make them doubt their judgment.

4. The Bobo Doll Experiment

The Bobo Doll Experiment was conducted by Dr. Albert Bandura, the proponent of social learning theory .

Back in the 1960s, the Nature vs. Nurture debate was a popular topic among psychologists. Bandura contributed to this discussion by proposing that human behavior is mostly influenced by environmental rather than genetic factors.

In the Bobo Doll Experiment, children were divided into three groups: one group was shown a video in which an adult acted aggressively toward the Bobo Doll, the second group was shown a video in which an adult play with the Bobo Doll, and the third group served as the control group where no video was shown.

The children were then led to a room with different kinds of toys, including the Bobo Doll they’ve seen in the video. Results showed that children tend to imitate the adults in the video. Those who were presented the aggressive model acted aggressively toward the Bobo Doll while those who were presented the passive model showed less aggression.

While the Bobo Doll Experiment can no longer be replicated because of ethical concerns, it has laid out the foundations of social learning theory and helped us understand the degree of influence adult behavior has on children.

5. Blue Eye / Brown Eye Experiment

Following the assassination of Martin Luther King Jr. in 1968, third-grade teacher Jane Elliott conducted an experiment in her class. Although not a formal experiment in controlled settings, A Class Divided is a good example of a social experiment to help children understand the concept of racism and discrimination.

The class was divided into two groups: blue-eyed children and brown-eyed children. For one day, Elliott gave preferential treatment to her blue-eyed students, giving them more attention and pampering them with rewards. The next day, it was the brown-eyed students’ turn to receive extra favors and privileges.

As a result, whichever group of students was given preferential treatment performed exceptionally well in class, had higher quiz scores, and recited more frequently; students who were discriminated against felt humiliated, answered poorly in tests, and became uncertain with their answers in class.

This study is now widely taught in sociocultural psychology classes.

6. Stanford Prison Experiment

One of the most controversial and widely-cited studies in psychology is the Stanford Prison Experiment , conducted by Philip Zimbardo at the basement of the Stanford psychology building in 1971. The hypothesis was that abusive behavior in prisons is influenced by the personality traits of the prisoners and prison guards.

The participants in the experiment were college students who were randomly assigned as either a prisoner or a prison guard. The prison guards were then told to run the simulated prison for two weeks. However, the experiment had to be stopped in just 6 days.

The prison guards abused their authority and harassed the prisoners through verbal and physical means. The prisoners, on the other hand, showed submissive behavior. Zimbardo decided to stop the experiment because the prisoners were showing signs of emotional and physical breakdown.

Although the experiment wasn’t completed, the results strongly showed that people can easily get into a social role when others expect them to, especially when it’s highly stereotyped .

7. The Halo Effect

Have you ever wondered why toothpastes and other dental products are endorsed in advertisements by celebrities more often than dentists? The Halo Effect is one of the reasons!

The Halo Effect shows how one favorable attribute of a person can gain them positive perceptions in other attributes. In the case of product advertisements, attractive celebrities are also perceived as intelligent and knowledgeable of a certain subject matter even though they’re not technically experts.

The Halo Effect originated in a classic study done by Edward Thorndike in the early 1900s. He asked military commanding officers to rate their subordinates based on different qualities, such as physical appearance, leadership, dependability, and intelligence.

The results showed that high ratings of a particular quality influences the ratings of other qualities, producing a halo effect of overall high ratings. The opposite also applied, which means that a negative rating in one quality also correlated to negative ratings in other qualities.

Experiments on the Halo Effect came in various formats as well, supporting Thorndike’s original theory. This phenomenon suggests that our perception of other people’s overall personality is hugely influenced by a quality that we focus on.

8. Cognitive Dissonance

There are experiences in our lives when our beliefs and behaviors do not align with each other and we try to justify them in our minds. This is cognitive dissonance , which was studied in an experiment by Leon Festinger and James Carlsmith back in 1959.

In this experiment, participants had to go through a series of boring and repetitive tasks, such as spending an hour turning pegs in a wooden knob. After completing the tasks, they were then paid either $1 or $20 to tell the next participants that the tasks were extremely fun and enjoyable. Afterwards, participants were asked to rate the experiment. Those who were given $1 rated the experiment as more interesting and fun than those who received $20.

The results showed that those who received a smaller incentive to lie experienced cognitive dissonance — $1 wasn’t enough incentive for that one hour of painstakingly boring activity, so the participants had to justify that they had fun anyway.

Famous Case Studies in Psychology

9. little albert.

In 1920, behaviourist theorists John Watson and Rosalie Rayner experimented on a 9-month-old baby to test the effects of classical conditioning in instilling fear in humans.

This was such a controversial study that it gained popularity in psychology textbooks and syllabi because it is a classic example of unethical research studies done in the name of science.

In one of the experiments, Little Albert was presented with a harmless stimulus or object, a white rat, which he wasn’t scared of at first. But every time Little Albert would see the white rat, the researchers would play a scary sound of hammer and steel. After about 6 pairings, Little Albert learned to fear the rat even without the scary sound.

Little Albert developed signs of fear to different objects presented to him through classical conditioning . He even generalized his fear to other stimuli not present in the course of the experiment.

10. Phineas Gage

Phineas Gage is such a celebrity in Psych 101 classes, even though the way he rose to popularity began with a tragic accident. He was a resident of Central Vermont and worked in the construction of a new railway line in the mid-1800s. One day, an explosive went off prematurely, sending a tamping iron straight into his face and through his brain.

Gage survived the accident, fortunately, something that is considered a feat even up to this day. He managed to find a job as a stagecoach after the accident. However, his family and friends reported that his personality changed so much that “he was no longer Gage” (Harlow, 1868).

New evidence on the case of Phineas Gage has since come to light, thanks to modern scientific studies and medical tests. However, there are still plenty of mysteries revolving around his brain damage and subsequent recovery.

11. Anna O.

Anna O., a social worker and feminist of German Jewish descent, was one of the first patients to receive psychoanalytic treatment.

Her real name was Bertha Pappenheim and she inspired much of Sigmund Freud’s works and books on psychoanalytic theory, although they hadn’t met in person. Their connection was through Joseph Breuer, Freud’s mentor when he was still starting his clinical practice.

Anna O. suffered from paralysis, personality changes, hallucinations, and rambling speech, but her doctors could not find the cause. Joseph Breuer was then called to her house for intervention and he performed psychoanalysis, also called the “talking cure”, on her.

Breuer would tell Anna O. to say anything that came to her mind, such as her thoughts, feelings, and childhood experiences. It was noted that her symptoms subsided by talking things out.

However, Breuer later referred Anna O. to the Bellevue Sanatorium, where she recovered and set out to be a renowned writer and advocate of women and children.

12. Patient HM

H.M., or Henry Gustav Molaison, was a severe amnesiac who had been the subject of countless psychological and neurological studies.

Henry was 27 when he underwent brain surgery to cure the epilepsy that he had been experiencing since childhood. In an unfortunate turn of events, he lost his memory because of the surgery and his brain also became unable to store long-term memories.

He was then regarded as someone living solely in the present, forgetting an experience as soon as it happened and only remembering bits and pieces of his past. Over the years, his amnesia and the structure of his brain had helped neuropsychologists learn more about cognitive functions .

Suzanne Corkin, a researcher, writer, and good friend of H.M., recently published a book about his life. Entitled Permanent Present Tense , this book is both a memoir and a case study following the struggles and joys of Henry Gustav Molaison.

13. Chris Sizemore

Chris Sizemore gained celebrity status in the psychology community when she was diagnosed with multiple personality disorder, now known as dissociative identity disorder.

Sizemore has several alter egos, which included Eve Black, Eve White, and Jane. Various papers about her stated that these alter egos were formed as a coping mechanism against the traumatic experiences she underwent in her childhood.

Sizemore said that although she has succeeded in unifying her alter egos into one dominant personality, there were periods in the past experienced by only one of her alter egos. For example, her husband married her Eve White alter ego and not her.

Her story inspired her psychiatrists to write a book about her, entitled The Three Faces of Eve , which was then turned into a 1957 movie of the same title.

14. David Reimer

When David was just 8 months old, he lost his penis because of a botched circumcision operation.

Psychologist John Money then advised Reimer’s parents to raise him as a girl instead, naming him Brenda. His gender reassignment was supported by subsequent surgery and hormonal therapy.

Money described Reimer’s gender reassignment as a success, but problems started to arise as Reimer was growing up. His boyishness was not completely subdued by the hormonal therapy. When he was 14 years old, he learned about the secrets of his past and he underwent gender reassignment to become male again.

Reimer became an advocate for children undergoing the same difficult situation he had been. His life story ended when he was 38 as he took his own life.

15. Kim Peek

Kim Peek was the inspiration behind Rain Man , an Oscar-winning movie about an autistic savant character played by Dustin Hoffman.

The movie was released in 1988, a time when autism wasn’t widely known and acknowledged yet. So it was an eye-opener for many people who watched the film.

In reality, Kim Peek was a non-autistic savant. He was exceptionally intelligent despite the brain abnormalities he was born with. He was like a walking encyclopedia, knowledgeable about travel routes, US zip codes, historical facts, and classical music. He also read and memorized approximately 12,000 books in his lifetime.

This list of experiments and case studies in psychology is just the tip of the iceberg! There are still countless interesting psychology studies that you can explore if you want to learn more about human behavior and dynamics.

You can also conduct your own mini-experiment or participate in a study conducted in your school or neighborhood. Just remember that there are ethical standards to follow so as not to repeat the lasting physical and emotional harm done to Little Albert or the Stanford Prison Experiment participants.

Asch, S. E. (1956). Studies of independence and conformity: I. A minority of one against a unanimous majority. Psychological Monographs: General and Applied, 70 (9), 1–70. https://doi.org/10.1037/h0093718

Bandura, A., Ross, D., & Ross, S. A. (1961). Transmission of aggression through imitation of aggressive models. The Journal of Abnormal and Social Psychology, 63 (3), 575–582. https://doi.org/10.1037/h0045925

Elliott, J., Yale University., WGBH (Television station : Boston, Mass.), & PBS DVD (Firm). (2003). A class divided. New Haven, Conn.: Yale University Films.

Festinger, L., & Carlsmith, J. M. (1959). Cognitive consequences of forced compliance. The Journal of Abnormal and Social Psychology, 58 (2), 203–210. https://doi.org/10.1037/h0041593

Haney, C., Banks, W. C., & Zimbardo, P. G. (1973). A study of prisoners and guards in a simulated prison. Naval Research Review , 30 , 4-17.

Latane, B., & Darley, J. M. (1968). Group inhibition of bystander intervention in emergencies. Journal of Personality and Social Psychology, 10 (3), 215–221. https://doi.org/10.1037/h0026570

Mischel, W. (2014). The Marshmallow Test: Mastering self-control. Little, Brown and Co.

Thorndike, E. (1920) A Constant Error in Psychological Ratings. Journal of Applied Psychology , 4 , 25-29. http://dx.doi.org/10.1037/h0071663

Watson, J. B., & Rayner, R. (1920). Conditioned emotional reactions. Journal of experimental psychology , 3 (1), 1.

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Uncovering the Significance and Applications of Natural Experiments in Psychology

Have you ever wondered how psychologists conduct research in real-life settings to understand human behavior? Natural experiments in psychology offer a unique opportunity to study behavior in naturalistic settings, allowing for causal inferences and ethical considerations.

In this article, we will explore the types of natural experiments, such as quasi-experiments and interrupted time-series designs, and delve into their applications in studying environmental factors, policy changes, natural disasters, cultural differences, and genetics on behavior. Let’s uncover the significance and applications of natural experiments in psychology.

• Natural experiments in psychology allow for causal inference and provide a naturalistic setting for studying behavior.
• Natural experiments are important for ethical considerations and can be used to study the effects of environmental, policy, and cultural factors on behavior.
• Types of natural experiments include quasi-experiments, interrupted time-series designs, and naturalistic observations, among others.
• 1 What Are Natural Experiments in Psychology?
• 2.1 Provide a Naturalistic Setting
• 2.2 Allow for Causal Inference
• 2.3 Ethical Considerations
• 3.1 Quasi-Experiments
• 3.2 Interrupted Time-Series Designs
• 3.3 Regression Discontinuity Designs
• 3.4 Instrumental Variables Designs
• 3.5 Naturalistic Observations
• 4.1 Studying the Effects of Environmental Factors on Behavior
• 4.2 Examining the Effects of Policy Changes on Mental Health
• 4.3 Investigating the Impact of Natural Disasters on Psychological Well-being
• 4.4 Studying the Effects of Cultural Differences on Behavior
• 4.5 Exploring the Influence of Genetics on Behavior
• 5.1 What are natural experiments in psychology and why are they significant?
• 5.2 How are natural experiments different from other types of experiments in psychology?
• 5.3 What are some examples of natural experiments in psychology?
• 5.4 What are the advantages of using natural experiments in psychology?
• 5.5 What are the limitations of natural experiments in psychology?
• 5.6 In what ways can the findings from natural experiments in psychology be applied?

What Are Natural Experiments in Psychology?

Natural experiments in psychology refer to research studies that leverage real-world settings and conditions to investigate causality and observe the impact of various factors on psychiatric disorders.

Real-world settings provide a unique platform for researchers to study phenomena in a more authentic and natural environment.

By allowing events to unfold naturally, researchers can gain insights into how genetic and environmental factors interact to influence mental health outcomes.

For instance, a study examining the prevalence of anxiety disorders among individuals living in areas prone to natural disasters would be considered a natural experiment.

This approach enables researchers to gather valuable data without directly manipulating variables, offering a clearer understanding of the complex relationships between different factors.

Why Are Natural Experiments Important in Psychology?

Natural experiments play a crucial role in psychology as they allow researchers to uncover causal relationships, identify risk factors, address confounding variables, and enhance the validity and reliability of their findings.

One of the significant advantages of natural experiments lies in their capacity to provide valuable insights into causal inference . By observing phenomena in real-world settings, researchers can gain a deeper understanding of how certain variables influence behavior or mental processes. This method helps in determining cause-and-effect relationships with more clarity compared to controlled lab experiments.

Natural experiments help mitigate the impact of confounding factors , which can distort research outcomes. By leveraging naturally occurring events or conditions, researchers can better isolate the effects of a specific variable on the phenomenon of interest.

The methodological rigor embedded in natural experiments is crucial for establishing valid and reliable research outcomes. It adds a layer of authenticity to the findings and ensures that the conclusions drawn are robust and applicable beyond the specific study.

Provide a Naturalistic Setting

Natural experiments offer a naturalistic setting for research, allowing for the observation of behavior and variables in real-world contexts with actual participants.

This type of research design provides researchers with a unique opportunity to study phenomena as they naturally unfold without the need for artificial manipulation or controlled laboratory conditions. By observing participants in their everyday environments, researchers can gain valuable insights into how individuals interact, make decisions, and respond to various stimuli in a more authentic manner.

Allow for Causal Inference

Natural experiments enable researchers to make causal inferences by examining the impact of exposures, genetic influences, environmental factors, and familial relationships on conditions such as ADHD.

Natural experiments provide a unique opportunity for researchers to study the impact of various factors on complex conditions like ADHD in a real-world setting. By observing individuals who are already exposed to certain influences, researchers can draw conclusions about causality without actively manipulating variables like in controlled experiments.

These studies can help researchers understand how genetic predispositions interact with environmental triggers to influence the development of ADHD. Through careful observation and data analysis, researchers can uncover correlations that suggest causal relationships between genetic factors, environmental exposures, and behavioral outcomes.

Ethical Considerations

When conducting natural experiments, researchers must address ethical issues to ensure the practicality of their studies while maintaining ethical standards, validity, and reliability in their research outcomes.

One key aspect of ethical considerations in natural experiments involves obtaining informed consent from participants, ensuring that they are aware of the potential risks and benefits of the study.

Researchers should strive to minimize any harm or discomfort to participants, prioritizing their well-being above all else.

Furthermore , transparency in research methods and reporting is crucial to promote accountability and credibility in scientific inquiries.

What Are the Types of Natural Experiments?

Various types of natural experiments exist in psychology, including observational studies, interrupted time-series designs, and regression discontinuity designs that allow researchers to investigate causal relationships.

Observational studies involve observing subjects in their natural environment without any interference from the researcher, providing valuable insights into behaviors and relationships.

Interrupted time-series designs involve collecting data before and after a specific intervention or event, allowing researchers to assess the impact of the intervention over time.

Regression discontinuity designs focus on studying the effects of a treatment or intervention by comparing subjects immediately above and below a predetermined threshold, such as a test score, providing a quasi-experimental method for establishing causal relationships in psychology.

Quasi-Experiments

Quasi-experiments are research studies that adopt a methodology similar to experimental designs but lack full control over variables, allowing researchers to draw findings from natural settings with actual participants.

Typically, in quasi-experiments, researchers manipulate an independent variable to observe its effects on a dependent variable. This allows for studying causal relationships in real-world contexts, providing valuable insights into how certain factors influence outcomes. By utilizing existing conditions instead of creating artificial settings, quasi-experiments offer practical applications and can be particularly useful in fields where strict control over variables is not feasible.

Despite their advantages, quasi-experiments often face criticism for potential confounding variables and threats to internal validity, leading researchers to employ various statistical techniques to address bias and enhance the credibility of their findings.

Interrupted Time-Series Designs

Interrupted time-series designs in research involve the collection of data over time, with interventions or interruptions implemented to observe the impact on variables, providing tangible examples of causality.

These designs are valuable in studying causal relationships as they allow researchers to track changes in variables before and after interventions. By establishing a baseline trend, the effects of the intervention can be clearly identified. For example, in a public health study, researchers might track the incidence of a specific disease before and after the implementation of a vaccination program. This method helps in determining the effectiveness of the intervention by comparing pre- and post-intervention data.

Regression Discontinuity Designs

Regression discontinuity designs are research methods that focus on studying causal inference by analyzing outcomes before and after a threshold, offering both advantages and disadvantages in establishing causality.

In a regression discontinuity design, the treatment or intervention is determined based on a cutoff point or threshold. This unique approach allows researchers to observe the causal effect of the treatment by comparing outcomes just above and just below the threshold.

• One of the strengths of this design is its ability to account for potential confounding variables near the threshold, making it easier to attribute changes in outcomes to the treatment.
• A limitation of regression discontinuity designs is the assumption of a linear relationship near the threshold, which may not always hold true in real-world scenarios.

For example, researchers may use this design to evaluate the impact of a new educational policy by examining the academic performance of students who just passed or failed a qualifying exam.

Instrumental Variables Designs

Instrumental variables designs are research methodologies that use instrumental variables as proxies to establish causal relationships between independent and dependent variables, aiding in drawing critical findings.

Through this approach, researchers can address issues with endogeneity, measurement error, or omitted variable bias, which often hinder traditional observational studies from establishing causality. By finding suitable instrumental variables that affect the independent variable but are unrelated to the dependent variable except through the independent variable, researchers can overcome biases and identify causal effects more reliably.

Instrumental variables design allows researchers to infer causal relationships in situations where randomized controlled experiments are impractical or unethical. It provides a valuable tool for exploring complex social, economic, or health phenomena where true experimentation may not be feasible.

Naturalistic Observations

Naturalistic observations involve studying behavior in its natural state without artificial manipulation, providing valuable insights into variables affecting individuals’ actions.

Observing behaviors in real-world settings allows psychologists to understand how individuals react to various stimuli without the constraints of lab environments. This method enables researchers to witness spontaneous behaviors and interactions as they naturally occur, offering a more authentic representation of human behavior. By observing individuals in their natural habitat, psychologists can gain a deeper understanding of the influence of social, environmental, and situational factors on behavior. Naturalistic observations help in identifying patterns, trends, and dynamics that may not surface in controlled experimental settings.

What Are the Applications of Natural Experiments in Psychology?

Natural experiments find diverse applications in psychology, including studying the effects of environmental factors on behavior, exploring the impact of traumatic experiences, and conducting field experiments to understand human responses.

Researchers use natural experiments to observe how individuals respond to situational constraints without direct manipulation by the experimenter. These studies help in understanding how real-world factors such as socioeconomic status, urban environments, or natural disasters influence human behavior. For instance, they can investigate how exposure to green spaces affects stress levels or how community support impacts recovery from traumatic events.

In the context of mental health, natural experiments provide valuable insights into the long-term consequences of adversity and resilience mechanisms. By examining populations exposed to different levels of adversity, researchers can identify protective factors that buffer against psychological distress. This approach helps in designing interventions to support individuals facing similar challenges in the future.

Field experiments executed in naturalistic settings offer a unique opportunity to study human behavior in authentic environments. Researchers can observe spontaneous reactions to stimuli and interactions in real time, providing valuable data that may be difficult to capture in controlled laboratory settings. These experiments often involve observing group dynamics, social behaviors, or decision-making processes in public spaces, enhancing the understanding of how individuals interact with their surroundings.

Studying the Effects of Environmental Factors on Behavior

Natural experiments assist in investigating how environmental factors influence behavior within communities and shape individuals’ attitudes, offering valuable insights into social dynamics.

These types of studies are particularly useful in observing real-world scenarios where researchers do not manipulate the situation intentionally. By observing how certain events or changes in the environment affect people’s behavior and beliefs, researchers can draw conclusions about the impact of these external factors.

Natural experiments provide a more ethical approach to studying the effects of environmental variables since they occur naturally without any interference from researchers. This allows for a better understanding of how individuals respond to changes in their surroundings without artificial constraints.

Examining the Effects of Policy Changes on Mental Health

Natural experiments provide a platform for examining the effects of policy changes on mental health conditions such as depression, bipolar disorder, and schizophrenia, shedding light on the outcomes of varying interventions.

By leveraging naturally occurring events or policies as the experimental setting, researchers can observe real-world impacts on mental health without direct intervention, allowing for a more comprehensive understanding of how certain policies or changes influence psychological well-being. This methodology enables researchers to assess the effectiveness of interventions in a practical context, offering insights into which strategies are most beneficial in addressing these complex mental health conditions.

Investigating the Impact of Natural Disasters on Psychological Well-being

By studying the impact of natural disasters on psychological well-being, natural experiments offer insights into how genetic predispositions and environmental stressors interact to influence individuals’ mental health outcomes.

Researchers utilize natural experiments to observe the aftermath of natural disasters, allowing them to analyze how individuals with specific genetic makeups respond to varying levels of environmental stress that arise from catastrophic events.

These studies highlight the intricate relationship between nature and nurture, shedding light on how genetic factors can either amplify or mitigate the psychological impacts of traumatic incidents.

Through these investigations, scientists aim to unravel the complexities of human resilience in the face of adversity, providing valuable knowledge for developing effective interventions and support systems for those affected by such crises.

Studying the Effects of Cultural Differences on Behavior

Natural experiments are instrumental in investigating how cultural differences influence behavior across genders and age groups, providing valuable insights into the diversity of human responses.

These experimental studies involve observing and analyzing individuals’ behaviors without any direct manipulation by researchers, allowing cultural variations to naturally influence the participants’ actions and reactions. By comparing these natural variations in different cultural settings, psychologists can gain a deeper understanding of how societal norms, values, and expectations shape behaviors, especially in relation to gender roles and age-related behaviors.

Exploring the Influence of Genetics on Behavior

Through the study of twins and genetic factors, natural experiments help researchers explore the influence of genetics and environmental interactions on behavior, uncovering critical insights into the complexities of human traits.

Natural experiments play a pivotal role in shedding light on how our genetic predispositions interact with the environment to shape our behavior. By comparing identical and fraternal twins raised in different environments, researchers can isolate the impact of genetics versus environmental influences.

Genetic analyses complement these studies by pinpointing specific genes that may contribute to certain behaviors or traits. This comprehensive approach of combining twin studies and genetic analyses allows scientists to delve deeper into the intricate mechanisms underlying human behavior.

Frequently Asked Questions

What are natural experiments in psychology and why are they significant.

Natural experiments in psychology are studies that take advantage of naturally occurring events or phenomena to investigate the relationship between variables. They are significant because they allow researchers to study the effects of variables in real-life settings, rather than in a controlled laboratory environment, which may not accurately reflect the complexities of the real world.

How are natural experiments different from other types of experiments in psychology?

Natural experiments differ from other types of experiments because they do not involve the manipulation of variables by the researcher. Instead, the variables occur naturally, and the researcher observes and measures their effects. This makes natural experiments more ecologically valid, as they reflect real-life situations.

What are some examples of natural experiments in psychology?

Some examples of natural experiments in psychology include studying the effects of natural disasters on mental health, observing the differences in social behavior between individuals living in urban and rural environments, and examining the impact of birth order on personality traits.

What are the advantages of using natural experiments in psychology?

One advantage of natural experiments is that they allow researchers to study variables that cannot be manipulated ethically or practically, such as the effects of poverty or early childhood experiences. They also provide more ecologically valid results, as they reflect real-life situations.

What are the limitations of natural experiments in psychology?

One limitation of natural experiments is that the variables may not occur frequently enough or in a controlled enough manner to draw reliable conclusions. Additionally, it may be challenging to control for confounding variables in natural experiments, as the researcher does not have control over the variables being studied.

In what ways can the findings from natural experiments in psychology be applied?

The findings from natural experiments in psychology can be applied in various ways, such as informing public policy, developing interventions or treatments, and improving understanding of real-life phenomena. They can also be used to validate or refute findings from laboratory experiments, providing a more comprehensive understanding of psychological processes.

Ethan Clarke holds a Master’s in Organizational Psychology and has spent years consulting for Fortune 500 companies. His expertise in workplace behavior and employee well-being has led to significant organizational changes and improved company cultures. Ethan is passionate about applying psychological principles to enhance productivity and job satisfaction. Through his writing, he aims to bridge the gap between academic research and practical application in the workplace, providing readers with actionable insights for professional growth and organizational development.

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Research Methods In Psychology

Saul McLeod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

Research methods in psychology are systematic procedures used to observe, describe, predict, and explain behavior and mental processes. They include experiments, surveys, case studies, and naturalistic observations, ensuring data collection is objective and reliable to understand and explain psychological phenomena.

Hypotheses are statements about the prediction of the results, that can be verified or disproved by some investigation.

There are four types of hypotheses :

• Null Hypotheses (H0 ) – these predict that no difference will be found in the results between the conditions. Typically these are written ‘There will be no difference…’
• Alternative Hypotheses (Ha or H1) – these predict that there will be a significant difference in the results between the two conditions. This is also known as the experimental hypothesis.
• One-tailed (directional) hypotheses – these state the specific direction the researcher expects the results to move in, e.g. higher, lower, more, less. In a correlation study, the predicted direction of the correlation can be either positive or negative.
• Two-tailed (non-directional) hypotheses – these state that a difference will be found between the conditions of the independent variable but does not state the direction of a difference or relationship. Typically these are always written ‘There will be a difference ….’

All research has an alternative hypothesis (either a one-tailed or two-tailed) and a corresponding null hypothesis.

Once the research is conducted and results are found, psychologists must accept one hypothesis and reject the other. 

So, if a difference is found, the Psychologist would accept the alternative hypothesis and reject the null.  The opposite applies if no difference is found.

Sampling techniques

Sampling is the process of selecting a representative group from the population under study.

A sample is the participants you select from a target population (the group you are interested in) to make generalizations about.

Representative means the extent to which a sample mirrors a researcher’s target population and reflects its characteristics.

Generalisability means the extent to which their findings can be applied to the larger population of which their sample was a part.

• Volunteer sample : where participants pick themselves through newspaper adverts, noticeboards or online.
• Opportunity sampling : also known as convenience sampling , uses people who are available at the time the study is carried out and willing to take part. It is based on convenience.
• Random sampling : when every person in the target population has an equal chance of being selected. An example of random sampling would be picking names out of a hat.
• Systematic sampling : when a system is used to select participants. Picking every Nth person from all possible participants. N = the number of people in the research population / the number of people needed for the sample.
• Stratified sampling : when you identify the subgroups and select participants in proportion to their occurrences.
• Snowball sampling : when researchers find a few participants, and then ask them to find participants themselves and so on.
• Quota sampling : when researchers will be told to ensure the sample fits certain quotas, for example they might be told to find 90 participants, with 30 of them being unemployed.

Experiments always have an independent and dependent variable .

• The independent variable is the one the experimenter manipulates (the thing that changes between the conditions the participants are placed into). It is assumed to have a direct effect on the dependent variable.
• The dependent variable is the thing being measured, or the results of the experiment.

Operationalization of variables means making them measurable/quantifiable. We must use operationalization to ensure that variables are in a form that can be easily tested.

For instance, we can’t really measure ‘happiness’, but we can measure how many times a person smiles within a two-hour period. 

By operationalizing variables, we make it easy for someone else to replicate our research. Remember, this is important because we can check if our findings are reliable.

Extraneous variables are all variables which are not independent variable but could affect the results of the experiment.

It can be a natural characteristic of the participant, such as intelligence levels, gender, or age for example, or it could be a situational feature of the environment such as lighting or noise.

Demand characteristics are a type of extraneous variable that occurs if the participants work out the aims of the research study, they may begin to behave in a certain way.

For example, in Milgram’s research , critics argued that participants worked out that the shocks were not real and they administered them as they thought this was what was required of them. 

Extraneous variables must be controlled so that they do not affect (confound) the results.

Randomly allocating participants to their conditions or using a matched pairs experimental design can help to reduce participant variables. 

Situational variables are controlled by using standardized procedures, ensuring every participant in a given condition is treated in the same way

Experimental Design

Experimental design refers to how participants are allocated to each condition of the independent variable, such as a control or experimental group.

• Independent design ( between-groups design ): each participant is selected for only one group. With the independent design, the most common way of deciding which participants go into which group is by means of randomization. 
• Matched participants design : each participant is selected for only one group, but the participants in the two groups are matched for some relevant factor or factors (e.g. ability; sex; age).
• Repeated measures design ( within groups) : each participant appears in both groups, so that there are exactly the same participants in each group.
• The main problem with the repeated measures design is that there may well be order effects. Their experiences during the experiment may change the participants in various ways.
• They may perform better when they appear in the second group because they have gained useful information about the experiment or about the task. On the other hand, they may perform less well on the second occasion because of tiredness or boredom.
• Counterbalancing is the best way of preventing order effects from disrupting the findings of an experiment, and involves ensuring that each condition is equally likely to be used first and second by the participants.

If we wish to compare two groups with respect to a given independent variable, it is essential to make sure that the two groups do not differ in any other important way. 

Experimental Methods

All experimental methods involve an iv (independent variable) and dv (dependent variable)..

The researcher decides where the experiment will take place, at what time, with which participants, in what circumstances,  using a standardized procedure.

• Field experiments are conducted in the everyday (natural) environment of the participants. The experimenter still manipulates the IV, but in a real-life setting. It may be possible to control extraneous variables, though such control is more difficult than in a lab experiment.
• Natural experiments are when a naturally occurring IV is investigated that isn’t deliberately manipulated, it exists anyway. Participants are not randomly allocated, and the natural event may only occur rarely.

Case studies are in-depth investigations of a person, group, event, or community. It uses information from a range of sources, such as from the person concerned and also from their family and friends.

Many techniques may be used such as interviews, psychological tests, observations and experiments. Case studies are generally longitudinal: in other words, they follow the individual or group over an extended period of time. 

Case studies are widely used in psychology and among the best-known ones carried out were by Sigmund Freud . He conducted very detailed investigations into the private lives of his patients in an attempt to both understand and help them overcome their illnesses.

Case studies provide rich qualitative data and have high levels of ecological validity. However, it is difficult to generalize from individual cases as each one has unique characteristics.

Correlational Studies

Correlation means association; it is a measure of the extent to which two variables are related. One of the variables can be regarded as the predictor variable with the other one as the outcome variable.

Correlational studies typically involve obtaining two different measures from a group of participants, and then assessing the degree of association between the measures. 

The predictor variable can be seen as occurring before the outcome variable in some sense. It is called the predictor variable, because it forms the basis for predicting the value of the outcome variable.

Relationships between variables can be displayed on a graph or as a numerical score called a correlation coefficient.

• If an increase in one variable tends to be associated with an increase in the other, then this is known as a positive correlation .
• If an increase in one variable tends to be associated with a decrease in the other, then this is known as a negative correlation .
• A zero correlation occurs when there is no relationship between variables.

After looking at the scattergraph, if we want to be sure that a significant relationship does exist between the two variables, a statistical test of correlation can be conducted, such as Spearman’s rho.

The test will give us a score, called a correlation coefficient . This is a value between 0 and 1, and the closer to 1 the score is, the stronger the relationship between the variables. This value can be both positive e.g. 0.63, or negative -0.63.

A correlation between variables, however, does not automatically mean that the change in one variable is the cause of the change in the values of the other variable. A correlation only shows if there is a relationship between variables.

Correlation does not always prove causation, as a third variable may be involved. 

Interview Methods

Interviews are commonly divided into two types: structured and unstructured.

A fixed, predetermined set of questions is put to every participant in the same order and in the same way. 

Responses are recorded on a questionnaire, and the researcher presets the order and wording of questions, and sometimes the range of alternative answers.

The interviewer stays within their role and maintains social distance from the interviewee.

There are no set questions, and the participant can raise whatever topics he/she feels are relevant and ask them in their own way. Questions are posed about participants’ answers to the subject

Unstructured interviews are most useful in qualitative research to analyze attitudes and values.

Though they rarely provide a valid basis for generalization, their main advantage is that they enable the researcher to probe social actors’ subjective point of view. 

Questionnaire Method

Questionnaires can be thought of as a kind of written interview. They can be carried out face to face, by telephone, or post.

The choice of questions is important because of the need to avoid bias or ambiguity in the questions, ‘leading’ the respondent or causing offense.

• Open questions are designed to encourage a full, meaningful answer using the subject’s own knowledge and feelings. They provide insights into feelings, opinions, and understanding. Example: “How do you feel about that situation?”
• Closed questions can be answered with a simple “yes” or “no” or specific information, limiting the depth of response. They are useful for gathering specific facts or confirming details. Example: “Do you feel anxious in crowds?”

Its other practical advantages are that it is cheaper than face-to-face interviews and can be used to contact many respondents scattered over a wide area relatively quickly.

Observations

There are different types of observation methods :

• Covert observation is where the researcher doesn’t tell the participants they are being observed until after the study is complete. There could be ethical problems or deception and consent with this particular observation method.
• Overt observation is where a researcher tells the participants they are being observed and what they are being observed for.
• Controlled : behavior is observed under controlled laboratory conditions (e.g., Bandura’s Bobo doll study).
• Natural : Here, spontaneous behavior is recorded in a natural setting.
• Participant : Here, the observer has direct contact with the group of people they are observing. The researcher becomes a member of the group they are researching.  
• Non-participant (aka “fly on the wall): The researcher does not have direct contact with the people being observed. The observation of participants’ behavior is from a distance

Pilot Study

A pilot  study is a small scale preliminary study conducted in order to evaluate the feasibility of the key s teps in a future, full-scale project.

A pilot study is an initial run-through of the procedures to be used in an investigation; it involves selecting a few people and trying out the study on them. It is possible to save time, and in some cases, money, by identifying any flaws in the procedures designed by the researcher.

A pilot study can help the researcher spot any ambiguities (i.e. unusual things) or confusion in the information given to participants or problems with the task devised.

Sometimes the task is too hard, and the researcher may get a floor effect, because none of the participants can score at all or can complete the task – all performances are low.

The opposite effect is a ceiling effect, when the task is so easy that all achieve virtually full marks or top performances and are “hitting the ceiling”.

Research Design

In cross-sectional research , a researcher compares multiple segments of the population at the same time

Sometimes, we want to see how people change over time, as in studies of human development and lifespan. Longitudinal research is a research design in which data-gathering is administered repeatedly over an extended period of time.

In cohort studies , the participants must share a common factor or characteristic such as age, demographic, or occupation. A cohort study is a type of longitudinal study in which researchers monitor and observe a chosen population over an extended period.

Triangulation means using more than one research method to improve the study’s validity.

Reliability

Reliability is a measure of consistency, if a particular measurement is repeated and the same result is obtained then it is described as being reliable.

• Test-retest reliability :  assessing the same person on two different occasions which shows the extent to which the test produces the same answers.
• Inter-observer reliability : the extent to which there is an agreement between two or more observers.

Meta-Analysis

Meta-analysis is a statistical procedure used to combine and synthesize findings from multiple independent studies to estimate the average effect size for a particular research question.

Meta-analysis goes beyond traditional narrative reviews by using statistical methods to integrate the results of several studies, leading to a more objective appraisal of the evidence.

This is done by looking through various databases, and then decisions are made about what studies are to be included/excluded.

• Strengths : Increases the conclusions’ validity as they’re based on a wider range.
• Weaknesses : Research designs in studies can vary, so they are not truly comparable.

Peer Review

A researcher submits an article to a journal. The choice of the journal may be determined by the journal’s audience or prestige.

The journal selects two or more appropriate experts (psychologists working in a similar field) to peer review the article without payment. The peer reviewers assess: the methods and designs used, originality of the findings, the validity of the original research findings and its content, structure and language.

Feedback from the reviewer determines whether the article is accepted. The article may be: Accepted as it is, accepted with revisions, sent back to the author to revise and re-submit or rejected without the possibility of submission.

The editor makes the final decision whether to accept or reject the research report based on the reviewers comments/ recommendations.

Peer review is important because it prevent faulty data from entering the public domain, it provides a way of checking the validity of findings and the quality of the methodology and is used to assess the research rating of university departments.

Peer reviews may be an ideal, whereas in practice there are lots of problems. For example, it slows publication down and may prevent unusual, new work being published. Some reviewers might use it as an opportunity to prevent competing researchers from publishing work.

Some people doubt whether peer review can really prevent the publication of fraudulent research.

The advent of the internet means that a lot of research and academic comment is being published without official peer reviews than before, though systems are evolving on the internet where everyone really has a chance to offer their opinions and police the quality of research.

Types of Data

• Quantitative data is numerical data e.g. reaction time or number of mistakes. It represents how much or how long, how many there are of something. A tally of behavioral categories and closed questions in a questionnaire collect quantitative data.
• Qualitative data is virtually any type of information that can be observed and recorded that is not numerical in nature and can be in the form of written or verbal communication. Open questions in questionnaires and accounts from observational studies collect qualitative data.
• Primary data is first-hand data collected for the purpose of the investigation.
• Secondary data is information that has been collected by someone other than the person who is conducting the research e.g. taken from journals, books or articles.

Validity means how well a piece of research actually measures what it sets out to, or how well it reflects the reality it claims to represent.

Validity is whether the observed effect is genuine and represents what is actually out there in the world.

• Concurrent validity is the extent to which a psychological measure relates to an existing similar measure and obtains close results. For example, a new intelligence test compared to an established test.
• Face validity : does the test measure what it’s supposed to measure ‘on the face of it’. This is done by ‘eyeballing’ the measuring or by passing it to an expert to check.
• Ecological validit y is the extent to which findings from a research study can be generalized to other settings / real life.
• Temporal validity is the extent to which findings from a research study can be generalized to other historical times.

Features of Science

• Paradigm – A set of shared assumptions and agreed methods within a scientific discipline.
• Paradigm shift – The result of the scientific revolution: a significant change in the dominant unifying theory within a scientific discipline.
• Objectivity – When all sources of personal bias are minimised so not to distort or influence the research process.
• Empirical method – Scientific approaches that are based on the gathering of evidence through direct observation and experience.
• Replicability – The extent to which scientific procedures and findings can be repeated by other researchers.
• Falsifiability – The principle that a theory cannot be considered scientific unless it admits the possibility of being proved untrue.

Statistical Testing

A significant result is one where there is a low probability that chance factors were responsible for any observed difference, correlation, or association in the variables tested.

If our test is significant, we can reject our null hypothesis and accept our alternative hypothesis.

If our test is not significant, we can accept our null hypothesis and reject our alternative hypothesis. A null hypothesis is a statement of no effect.

In Psychology, we use p < 0.05 (as it strikes a balance between making a type I and II error) but p < 0.01 is used in tests that could cause harm like introducing a new drug.

A type I error is when the null hypothesis is rejected when it should have been accepted (happens when a lenient significance level is used, an error of optimism).

A type II error is when the null hypothesis is accepted when it should have been rejected (happens when a stringent significance level is used, an error of pessimism).

Ethical Issues

• Informed consent is when participants are able to make an informed judgment about whether to take part. It causes them to guess the aims of the study and change their behavior.
• To deal with it, we can gain presumptive consent or ask them to formally indicate their agreement to participate but it may invalidate the purpose of the study and it is not guaranteed that the participants would understand.
• Deception should only be used when it is approved by an ethics committee, as it involves deliberately misleading or withholding information. Participants should be fully debriefed after the study but debriefing can’t turn the clock back.
• All participants should be informed at the beginning that they have the right to withdraw if they ever feel distressed or uncomfortable.
• It causes bias as the ones that stayed are obedient and some may not withdraw as they may have been given incentives or feel like they’re spoiling the study. Researchers can offer the right to withdraw data after participation.
• Participants should all have protection from harm . The researcher should avoid risks greater than those experienced in everyday life and they should stop the study if any harm is suspected. However, the harm may not be apparent at the time of the study.
• Confidentiality concerns the communication of personal information. The researchers should not record any names but use numbers or false names though it may not be possible as it is sometimes possible to work out who the researchers were.