Types of Experiment in Psychology: Lab, Field, Natural, Quasi

In one of psychology’s best-known field experiments, 21 of 22 hospital nurses were ready to give a patient double the maximum dose of an unfamiliar drug, simply because a stranger claiming to be a doctor phoned and told them to.

The experiment is the only research method in psychology that can show one thing causes another. But not every experiment looks the same. Some happen in a quiet university room with a stopwatch, some happen on a hospital ward or a busy street without anyone knowing they are taking part, and some happen when a researcher spots a change in the world, such as a new law or the arrival of television, and measures what it does. The AQA specification groups these as “types of experiment, laboratory and field experiments; natural and quasi-experiments” (AQA, 2015).

Knowing the four types matters because the type of experiment decides what a study can and cannot tell you. It is separate from the experimental design, which is about how participants are split between conditions, and it has a direct effect on validity: the more control a researcher has, the more confident they can be about cause and effect, and the less the study usually looks like everyday life.

This guide explains what makes a study an experiment, then takes each type in turn with a definition, a real example, and its strengths and weaknesses. It compares laboratory with field experiments and natural with quasi-experiments, the two pairs students most often mix up, and ends with a quick method for identifying any experiment, a scenario quiz and advice on exam questions.

What Are the Types of Experiment in Psychology?

The four types of experiment in psychology are laboratory experiments, field experiments, natural experiments and quasi-experiments. They differ in two ways: whether the researcher deliberately manipulates the independent variable, and whether the study takes place in a controlled setting or in the participants’ everyday environment.

• Laboratory experiment: the researcher manipulates the independent variable in a controlled, artificial setting.
• Field experiment: the researcher manipulates the independent variable in a natural, everyday setting.
• Natural experiment: the independent variable changes naturally, because of an event the researcher did not cause, and the researcher measures its effect.
• Quasi-experiment: the independent variable is a difference that already exists between people, such as age, gender or a diagnosis, so it cannot be manipulated at all.

What Makes a Study an Experiment?

A study is an experiment when it compares conditions of an independent variable (IV) and measures the effect on a dependent variable (DV), while keeping other variables as constant as possible. The IV is the thing that changes between conditions, and the DV is the behaviour or outcome that is measured. If the DV differs between conditions and everything else was the same, the difference can be put down to the IV.

For example, if a researcher wants to know whether background music affects revision, the IV is the music (music or silence) and the DV might be the number of facts recalled in a test. The researcher would try to keep the room, the time of day, the material and the test the same in both conditions, so that the only thing that differs is the music. Anything else that could affect recall, such as tiredness or prior knowledge, is an extraneous variable, and if it changes systematically with the IV it becomes a confounding variable that ruins the comparison.

A proper experiment normally starts with a clear, testable prediction. Writing one well is covered in our guide to aims and hypotheses in psychology.

True Experiments and Quasi-Experiments

A true experiment is one in which the researcher manipulates the IV and randomly allocates participants to conditions. Random allocation matters because it spreads participant differences, such as intelligence, mood or motivation, evenly across the conditions, so they cannot explain the result. In the standard research methods text on the subject, Shadish, Cook and Campbell (2002) define a quasi-experiment as one that lacks random assignment to conditions.

Laboratory and field experiments are usually true experiments. Natural and quasi-experiments are not, because the researcher cannot decide who experiences the IV: nature, circumstance or the participants’ own characteristics have already decided. This is the single most useful idea for understanding the four types, and it explains why natural and quasi-experiments are weaker at showing cause and effect.

The Four Types of Experiment Compared

The four types of experiment can be compared on who controls the IV, where the study happens, whether participants can be randomly allocated and how much control the researcher has over extraneous variables. The table summarises the pattern, and each type is explained in full below.

Notice that the setting does not decide the type on its own. A quasi-experiment can take place in a laboratory, and a natural experiment can involve participants being tested in a laboratory after the event. What decides the type is the IV: who changed it, or whether it could be changed at all.

What Is a Laboratory Experiment?

A laboratory experiment is an experiment carried out in a controlled environment, where the researcher manipulates the independent variable, measures the dependent variable and controls extraneous variables as tightly as possible. Participants usually know they are in a study, and the procedure is standardised so that every participant has the same experience apart from the IV.

“Laboratory” does not have to mean a room full of scientific equipment. A classroom, an office or a quiet room in a school counts, as long as the researcher controls the setting and the participants have come to it for the purpose of the study. What makes it a laboratory experiment is the control, not the white coats.

Laboratory Experiment Example: Loftus and Palmer (1974)

Loftus and Palmer (1974) is a textbook laboratory experiment. Students watched short films of traffic accidents and then answered questions about them. The IV was the verb in one critical question: “About how fast were the cars going when they smashed into each other?” For other participants the verb was collided, bumped, hit or contacted. The DV was the speed they estimated.

The wording changed the answers. Participants asked about cars that “smashed” estimated an average of about 41 mph, while those asked about cars that “contacted” each other estimated under 32 mph. In a second experiment a week later, 16 of the 50 participants in the “smashed” condition said they had seen broken glass, compared with 7 of 50 in the “hit” condition, even though there was no broken glass in the film (Loftus & Palmer, 1974). You can read the full study in our guide to Loftus and Palmer’s car crash experiment.

Everything else was held constant: the same films, the same questionnaire and the same instructions. That control is what lets us say the verb, and nothing else, caused the difference. Other classic laboratory experiments include Milgram’s obedience study and Bandura’s Bobo doll research on imitation.

Strengths of Laboratory Experiments

• Cause and effect. Laboratory experiments offer the most control of any type, so researchers can be confident the IV caused the change in the DV. This is high internal validity.
• Replication. A standardised procedure can be written down and repeated exactly by other researchers, which lets them check whether a finding is reliable.
• Precise measurement. Researchers can use accurate equipment and measures, such as reaction times in milliseconds or exact recall scores, which are hard to collect in the outside world.
• Random allocation. Participants can be randomly allocated to conditions, which reduces the chance that participant variables explain the results.
• Easier ethics. Participants can give informed consent in advance and be fully debriefed afterwards.

Weaknesses of Laboratory Experiments

• Low ecological validity. An artificial setting may produce behaviour that people would not show in everyday life, so the results may not generalise beyond the laboratory.
• Low mundane realism. The task itself is often unlike real life. Watching a short film clip and estimating speed on a questionnaire is not the same as witnessing a real crash, with the fear, noise and consequences that go with it.
• Demand characteristics. Participants know they are being studied and may try to work out the aim and behave accordingly. Orne (1962) argued that a psychological experiment is a social situation in its own right, and that participants’ wish to be “good subjects” can shape what they do.
• Investigator effects. The researcher’s expectations, tone or body language can influence participants without anyone intending it.
• Narrow samples. Laboratory studies often rely on university students who volunteer, which limits how far results can be generalised to other groups.

What Is a Field Experiment?

A field experiment is an experiment carried out in a natural, everyday setting, where the researcher still manipulates the independent variable. The “field” is wherever the behaviour normally happens: a street, a school, a hospital, a train or a shop. Participants are often unaware they are taking part, which is the main reason field experiments produce more natural behaviour.

The defining feature is that the researcher still controls the IV. They decide who gets which condition, just as in a laboratory, but they give up control over the environment. That makes field experiments a middle ground: more realistic than the laboratory, but more controlled than a natural experiment.

Field Experiment Example: Hofling et al. (1966)

Hofling and colleagues (1966) tested obedience in a real hospital. A researcher phoned nurses on duty, claimed to be a doctor they had never met, and asked them to give a patient 20 mg of a drug called Astroten. The bottle, placed in the drug cabinet for the study, stated that the maximum daily dose was 10 mg. Hospital rules forbade taking instructions by phone from an unknown doctor, and the drug was not on the approved list.

Twenty-one of the 22 nurses were stopped on their way to give the drug (Hofling et al., 1966). Yet when the procedure was described to a separate group of nurses and nursing students and they were asked what they would do, almost all of them said they would refuse. The gap between what people say and what they do in a real setting is exactly what field experiments can reveal and laboratory tasks or questionnaires can miss.

A later hospital study by Rank and Jacobson (1977), published as “a failure to replicate”, found much lower compliance when conditions were different, which shows how strongly field results depend on the particular setting.

More Field Experiment Examples

Bickman (1974), the power of a uniform. A researcher stopped passers-by in the street and asked them to do small tasks, such as picking up a paper bag or moving away from a bus stop. The IV was how the researcher was dressed: as a civilian, a milkman or a guard. People complied more with the guard than with either of the others (Bickman, 1974). The street was real and the people did not know they were in a study, but the researcher controlled the IV.

Piliavin, Rodin and Piliavin (1969), the subway Samaritan. On New York subway trains, a researcher collapsed in front of passengers. The IV was whether he appeared ill, carrying a cane, or drunk, carrying a bottle. Passengers helped the apparently ill man far more often and more quickly than the apparently drunk man, and the number of bystanders made little difference (Piliavin et al., 1969). That last result sits awkwardly with laboratory studies of the bystander effect, which found that more bystanders means less helping, and it is a good example of a field experiment testing whether a laboratory finding holds up in real life.

Strengths of Field Experiments

• Higher ecological validity. Behaviour happens in its normal setting, so findings are more likely to generalise to everyday life.
• Fewer demand characteristics. When participants do not know they are being studied, they cannot change their behaviour to fit what they think the researcher wants.
• Cause and effect is still possible. Because the researcher manipulates the IV and can often allocate conditions at random, field experiments keep much of the causal power of the laboratory.
• Real consequences. The situations involve real people, real stakes and real decisions, which is why field results such as Hofling’s are so striking.

Weaknesses of Field Experiments

• Less control. Weather, noise, other people and countless other extraneous variables can change from one trial to the next, making it harder to be sure the IV caused the result.
• Ethical problems. Participants usually cannot give informed consent, may be deceived, and may never be debriefed. Studies like Hofling’s could cause real distress, and there are wider questions about researching people in public without their knowledge. Our guide to social sensitivity and research ethics covers these issues.
• Hard to replicate. A real setting can never be recreated exactly, so repeating a field experiment and getting the same result is harder.
• Sampling problems. Researchers often cannot choose who passes by, so the sample may be biased by time, place and chance.
• Precise measurement is difficult. Researchers may have to rely on observation in busy conditions rather than accurate measures.

Lab vs Field Experiments: What’s the Difference?

The difference between a laboratory experiment and a field experiment is the setting. In both, the researcher manipulates the IV. In a laboratory experiment the setting is controlled and artificial, and participants know they are being studied. In a field experiment the setting is natural, extraneous variables are harder to control, and participants often do not know they are taking part.

Same Question, Different Settings

Obedience research shows how the setting can change a result. In Milgram’s original laboratory study at Yale University, 26 of 40 participants (65%) continued to the maximum 450-volt shock (Milgram, 1963). When Milgram moved the procedure to a run-down office in Bridgeport, with no visible link to the university, obedience fell to 47.5% (Milgram, 1974). The prestige of the setting was part of what produced the behaviour.

Hofling’s field experiment found even higher obedience than Milgram, in a real workplace where following a doctor’s orders is part of the job. Taken together, these studies show that neither setting gives “the true answer”. Each tells you what happens under a particular set of conditions, and comparing them tells you which conditions matter.

Do Laboratory Findings Hold Up in the Real World?

Laboratory findings often hold up in the real world, but not always, and it depends on the area of psychology. Anderson, Lindsay and Bushman (1999) compared laboratory and field results on 38 research topics drawn from 21 meta-analyses, covering aggression, helping, leadership, depression and memory, and found considerable agreement between the two. They concluded that the psychological laboratory has generally produced truths rather than trivialities.

Mitchell (2012) repeated and extended that analysis with 217 laboratory-field comparisons from 82 meta-analyses and found a more mixed picture. Laboratory results from industrial and organisational psychology predicted field results well, but effects found in social psychology laboratories were the most likely to change direction in the field, and large laboratory effects replicated more reliably than small ones. So the criticism that laboratory experiments “lack ecological validity” is too simple for an exam answer: it is truer for some topics than others, and it is something that can be tested rather than assumed.

What Is a Natural Experiment?

A natural experiment is a study in which the independent variable changes because of an event the researcher did not cause, and the researcher measures the effect of that change on a dependent variable. The IV might be a new law, a natural disaster, a change in school policy or the arrival of a new technology. The word “natural” refers to the IV occurring naturally, not to the setting.

Natural experiments let psychologists study things that would be impossible or unethical to manipulate. No ethics committee would allow a researcher to take television away from a community, place children in an institution or close a town’s hospital. When these things happen anyway, a researcher can compare people before and after the event, or compare those affected with similar people who were not.

Natural Experiment Example: Television Arrives on St Helena

St Helena is a remote British island in the South Atlantic, with a population of around 5,600 in 1994 and, until March 1995, no broadcast television. Charlton and colleagues video-recorded the free play of 3- to 8-year-olds in two school playgrounds four months before television arrived, and again five years afterwards (Charlton et al., 2000). The IV was the arrival of television; the DV was the children’s pro-social and anti-social behaviour, coded from the recordings.

Very little changed. Out of 64 before-and-after comparisons, only nine showed a significant shift, and none showed an increase in anti-social behaviour. The two changes in anti-social behaviour were decreases, both among boys (Charlton et al., 2000). The researchers suggested that a close-knit community with strong social controls may limit how far aggression learned from the screen is acted out. The study is a useful counterweight to laboratory findings on aggression and social learning. The full paper is available from the University of Gloucestershire.

The researchers could not decide whether or when St Helena got television, so they did not control the IV. That is what makes it a natural experiment rather than a field experiment, even though the children were filmed in their own playgrounds.

Natural Experiment Example: The English and Romanian Adoptees Study

Some Romanian children who spent their earliest months or years in severely depriving institutions were later adopted by families in the UK. Rutter and the English and Romanian Adoptees (ERA) study team followed 111 Romanian children adopted into the UK before the age of two and compared them at age four with 52 children adopted within the UK before six months of age (Rutter & ERA Study Team, 1998).

The Romanian children were severely delayed when they arrived, with about half below the third percentile for height, weight, head size and development. Children adopted before six months had almost completely caught up by age four. Those adopted later had also made large gains but still scored lower: a mean General Cognitive Index of 92, compared with 109 for the UK adoptees. Age at adoption was the strongest predictor of cognitive functioning (Rutter & ERA Study Team, 1998).

The IV, age at which a child left the institution, was decided by events, not by the researchers. Deliberately depriving children to test the effects would be unthinkable, which is why natural experiments are so valuable for questions about early development and attachment.

Strengths of Natural Experiments

• Ethical access to difficult questions. Natural experiments allow research on variables that could never be manipulated, such as deprivation, disasters or major social change.
• High ecological validity. The IV is a real event in people’s lives, so the findings relate directly to the real world.
• Fewer demand characteristics. The change in the IV has nothing to do with the research, so participants have little reason to act differently because of it.
• Large-scale and long-term effects. Natural experiments can follow the effects of an event on a whole community over years, which laboratory studies cannot do.

Weaknesses of Natural Experiments

• No random allocation. Participants are not randomly allocated to conditions, so the groups may differ in other ways. In the ERA study, children adopted later may have differed from those adopted early in health or the conditions they experienced.
• Confounding variables. Other things often change at the same time as the IV. Over five years on St Helena, the children, the schools and the wider world all changed as well as television.
• Rare and unrepeatable. A natural event may happen only once, so the study cannot be replicated, and the researcher has to wait for the opportunity to arise.
• Small or unusual samples. The people affected by a particular event may not be typical, which limits generalisation. St Helena’s close community is part of the explanation offered for its results.
• Weaker evidence of cause and effect. Without control of the IV, researchers can only be cautious about causal conclusions.

Natural Experiments Beyond Psychology

Natural experiments are used across the social sciences, not only in psychology. The 2021 Nobel Prize in Economic Sciences was awarded to David Card, Joshua Angrist and Guido Imbens, with Angrist and Imbens recognised for “their methodological contributions to the analysis of causal relationships”. The Nobel Prize announcement explains that the key is to use situations where chance events or policy changes lead to groups of people being treated differently, in a way that resembles a clinical trial (Royal Swedish Academy of Sciences, 2021).

What Is a Quasi-Experiment?

A quasi-experiment is a study in which the independent variable is a difference between people that already exists, such as age, gender, handedness, occupation or a diagnosis, so the researcher cannot manipulate it or randomly allocate participants to conditions. “Quasi” means “almost”: it is almost an experiment, because conditions are compared, but the researcher does not create them.

A quasi-experiment can still be highly controlled. It often takes place in a laboratory with a standardised procedure and precise measures. The only thing missing is control over who ends up in which condition, because participants are already one thing or the other. You cannot randomly assign someone to be 70 years old or to have a diagnosis of depression.

Quasi-Experiment Example: London Taxi Drivers

Maguire and colleagues (2000) used brain scans to compare licensed London taxi drivers with people who did not drive taxis. London taxi drivers have to learn the city’s streets in great detail to qualify. The posterior hippocampus, a brain area involved in spatial memory, was significantly larger in the taxi drivers, and its size was related to how long they had been driving a taxi (Maguire et al., 2000).

The IV, being a taxi driver or not, was an existing difference between people. The researchers could not assign some people to spend years learning London’s streets. The link between hippocampal size and time spent driving suggests the job changed the brain, but on its own a quasi-experiment cannot rule out the alternative explanation that people with a larger hippocampus are more likely to become, and stay, taxi drivers.

Other common quasi-experiments compare males and females on a task, children of different ages on a memory test, or people with and without a particular condition on a measure of attention. Whenever the IV is something about the participants themselves, it is a quasi-experiment.

Strengths of Quasi-Experiments

• Studying differences that matter. Quasi-experiments are the only way to compare groups defined by age, gender, culture or diagnosis, which are some of the most important questions in psychology.
• Controlled conditions. Because they are often carried out in a laboratory, quasi-experiments can keep the benefits of standardised procedures, precise measurement and replication.
• Ethical. The researcher does not have to impose anything harmful on participants, because the difference already exists.

Weaknesses of Quasi-Experiments

• No random allocation. The groups may differ in many ways besides the IV. Older and younger people differ in education, health and experience of technology as well as age.
• Cause and effect is uncertain. Because the IV was not manipulated, the researcher cannot be sure it caused the difference in the DV, or which way round any causal link goes.
• Risk of bias in interpretation. Comparing groups such as men and women can reinforce stereotypes if small or confounded differences are over-interpreted.
• Demand characteristics can still occur. Participants in a laboratory quasi-experiment know they are being studied, just as in a laboratory experiment.

Natural vs Quasi-Experiments: What’s the Difference?

The difference between a natural experiment and a quasi-experiment is where the IV comes from. In a natural experiment the IV is an event or change that happens to people, such as the arrival of television or a change in the law. In a quasi-experiment the IV is a characteristic that people already have, such as their age, gender or occupation. In neither case does the researcher manipulate the IV.

A quick test is to ask whether the IV could, in theory, have been assigned by someone. Television could, in principle, have been switched on for one island and not another, so its arrival is a natural experiment. Age or gender could never be assigned, so a comparison of age groups or genders is a quasi-experiment.

Why the Terms Get Confusing

Outside A level, researchers often use “quasi-experiment” as an umbrella term for any study without random allocation, which includes natural experiments. The St Helena paper itself refers to earlier television studies as “quasi-experimental” (Charlton et al., 2000), and you will also see the phrase “quasi-natural experiment”. The A level definitions are narrower and treat the two as separate types, so follow your specification in the exam.

Exam boards also differ in which types they list. AQA names all four types (AQA, 2015). OCR lists laboratory, field and quasi-experiments (OCR, 2026), and Edexcel refers to field and laboratory experiments in its methods section (Pearson Edexcel, 2015). Check your own specification so you know which terms you can be asked to define.

How to Identify the Type of Experiment

To identify the type of experiment, first identify the IV, then ask two questions: did the researcher manipulate it, and where did the study take place? Those two questions sort almost every scenario an exam can give you.

1. Find the IV. What is being compared between the conditions?
2. Did the researcher manipulate the IV? If yes, it is a laboratory or field experiment. Go to step 3. If no, go to step 4.
3. Was the setting controlled or everyday? A controlled setting the participants came to for the study means a laboratory experiment. The participants’ normal environment means a field experiment.
4. Is the IV an event or a characteristic? An event or change that happened to people means a natural experiment. A difference people already have, such as age or gender, means a quasi-experiment.

Watch out for the setting as a distraction. A quasi-experiment carried out in a laboratory is still a quasi-experiment, and a natural experiment where participants are tested in a laboratory is still a natural experiment. Always decide on the IV first.

Name That Experiment

Try the method on the ten scenarios below. Most are made up for practice, and each answer explains the clue that decides it.

Which Type of Experiment Should Researchers Use?

The right type of experiment depends on the research question, what can ethically be manipulated, and whether the priority is proving cause and effect or showing how behaviour works in real life. There is no single best type, and many areas of psychology build their evidence by combining several.

• If the aim is to establish cause and effect and the IV can be manipulated safely, a laboratory experiment gives the strongest evidence.
• If the concern is whether a finding happens in real life, a field experiment tests it where the behaviour normally occurs.
• If the IV cannot ethically be manipulated, such as deprivation or a disaster, a natural experiment takes advantage of events that happen anyway.
• If the IV is part of who people are, such as age or gender, a quasi-experiment is the only option.

The type of experiment is one decision among several. Researchers also choose an experimental design, a way of sampling participants, and later a statistical test, which depends on the design and the level of measurement. Our guide to which statistical test to use takes you through that step. When an IV cannot be studied with any type of experiment, researchers turn to other methods, such as correlations, observations or a case study.

How to Answer Types of Experiment Exam Questions

Exam questions on types of experiment usually ask you to identify the type used in a described study and justify your answer, or to evaluate the type in the context of that study. The marks come from linking your answer to the details of the scenario, not from reciting a general definition.

Identify and Justify

A typical question describes a study and asks you to identify the type of experiment and explain your choice. Name the type, then give the reason using the scenario: "This is a quasi-experiment because the IV, whether the participant is a child or an adult, is a pre-existing difference that the researcher could not manipulate." Naming the IV in your justification is what turns a guess into an answer that earns the second mark.

Evaluate in Context

When asked for a strength or limitation of the type of experiment used, make the point, explain it, and apply it to the study. For example: "A limitation of this field experiment is the lack of control over extraneous variables. Shoppers in the supermarket may have been in a hurry or distracted by other people, which could have affected whether they helped, rather than the researcher's clothing." A general point about field experiments, with no reference to the supermarket, would earn fewer marks.

Common Mistakes to Avoid

• Deciding by setting alone. A study in a school is not automatically a field experiment. If the IV is age, it is a quasi-experiment wherever it happens.
• Confusing "natural experiment" with "naturalistic observation". A naturalistic observation has no IV at all; a natural experiment has an IV that changes naturally.
• Confusing type with design. "Independent groups" and "repeated measures" are experimental designs, not types of experiment.
• Saying laboratory experiments "have no ecological validity". They can have lower ecological validity, but the evidence shows many laboratory findings do generalise. Avoid absolute statements.
• Forgetting random allocation. The lack of random allocation is the key weakness of natural and quasi-experiments, and it is the clearest way to explain why they are weaker at showing cause and effect.

Evaluation points about types of experiment often overlap with reliability and validity, so revise those topics together. The ability to replicate a laboratory experiment is a point about reliability; ecological validity is a point about validity.

Conclusion

The four types of experiment differ in who controls the independent variable and where the study takes place. Laboratory and field experiments both manipulate the IV, with the laboratory giving more control and the field more realism. Natural experiments study the effects of events researchers could not or should not create, and quasi-experiments compare groups that already differ. Each type answers a different kind of question, and the strongest conclusions in psychology come from findings that hold up across several types. Once a study has been carried out and written up, it faces one more check before it enters the scientific record: peer review.

Frequently Asked Questions

What are the 4 types of experiment in psychology?

Psychology recognises four types of experiment: laboratory, field, natural and quasi. In the first two, researchers deliberately change the independent variable, either in a controlled room or in everyday surroundings. In natural experiments an outside event changes it, and in quasi-experiments it is a characteristic participants already have, such as their age.

What is the difference between a natural and a quasi experiment?

A natural experiment measures the effect of something that happens to people, like a flood, a school closure or a new policy. A quasi-experiment compares people on something they already are, like male or female, young or old. Neither lets the researcher manipulate the independent variable or randomly allocate participants.

What is the difference between a lab and a field experiment?

Both involve the researcher manipulating the independent variable, so the difference lies in where they happen. A lab experiment uses a controlled setting that participants attend for the study. A field experiment happens in people's normal surroundings, such as a street or workplace, often without them knowing, which trades some control for more natural behaviour.

Is a natural experiment a true experiment?

No. A true experiment needs the researcher to manipulate the independent variable and randomly allocate participants to conditions. In a natural experiment an outside event does the manipulating and nobody chooses who is affected, so it cannot meet either requirement. That is why its conclusions about cause and effect are more tentative.

What is an example of a field experiment in psychology?

Bickman's 1974 study of uniforms is a clear example. A researcher dressed as a civilian, a milkman or a guard asked people in the street to do small tasks, and more people obeyed the guard. The setting was ordinary and the passers-by did not know they were in a study, yet the researcher controlled the independent variable, clothing.

What is a quasi experiment in simple terms?

It is a comparison between groups of people who already differ, where the researcher measures whether that difference goes with a difference in behaviour. Comparing the memory of 20-year-olds and 70-year-olds is one. The researcher cannot choose who is in which group, which is why it is only "almost" an experiment.

Which type of experiment has the highest ecological validity?

Natural and field experiments usually score highest, because the behaviour is measured in real-life settings and, for natural experiments, the independent variable is a real event. Lab and quasi-experiments carried out in controlled rooms tend to score lowest. Ecological validity still depends on the task, so a field study with an odd task may generalise poorly.

What is a quasi-natural experiment?

"Quasi-natural experiment" is a label used mainly in economics and the social sciences for a study that exploits a real-world event to create comparison groups without random assignment. It means much the same as a natural experiment. A level psychology does not use the term, so in an exam describe the study as a natural experiment.

References

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• Charlton, T., Panting, C., Davie, R., Coles, D., & Whitmarsh, L. (2000). Children's playground behaviour across five years of broadcast television: A naturalistic study in a remote community. Emotional and Behavioural Difficulties, 5(4), 4-12.
• Hofling, C. K., Brotzman, E., Dalrymple, S., Graves, N., & Pierce, C. M. (1966). An experimental study in nurse-physician relationships. The Journal of Nervous and Mental Disease, 143(2), 171-180.
• Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal Behavior, 13(5), 585-589.
• Maguire, E. A., Gadian, D. G., Johnsrude, I. S., Good, C. D., Ashburner, J., Frackowiak, R. S. J., & Frith, C. D. (2000). Navigation-related structural change in the hippocampi of taxi drivers. Proceedings of the National Academy of Sciences, 97(8), 4398-4403.
• Milgram, S. (1963). Behavioral study of obedience. Journal of Abnormal and Social Psychology, 67(4), 371-378.
• Milgram, S. (1974). Obedience to authority: An experimental view. Harper & Row.
• Mitchell, G. (2012). Revisiting truth or triviality: The external validity of research in the psychological laboratory. Perspectives on Psychological Science, 7(2), 109-117.
• OCR. (2026). A Level Psychology H567 specification (Version 1.5). OCR.
• Orne, M. T. (1962). On the social psychology of the psychological experiment: With particular reference to demand characteristics and their implications. American Psychologist, 17(11), 776-783.
• Pearson Edexcel. (2015). Pearson Edexcel Level 3 Advanced GCE in Psychology (9PS0) specification. Pearson.
• Piliavin, I. M., Rodin, J., & Piliavin, J. A. (1969). Good Samaritanism: An underground phenomenon? Journal of Personality and Social Psychology, 13(4), 289-299.
• Rank, S. G., & Jacobson, C. K. (1977). Hospital nurses' compliance with medication overdose orders: A failure to replicate. Journal of Health and Social Behavior, 18(2), 188-193.
• Royal Swedish Academy of Sciences. (2021). The Prize in Economic Sciences 2021: Press release. Nobel Prize Outreach.
• Rutter, M., & English and Romanian Adoptees (ERA) Study Team. (1998). Developmental catch-up, and deficit, following adoption after severe global early privation. Journal of Child Psychology and Psychiatry, 39(4), 465-476.
• Shadish, W. R., Cook, T. D., & Campbell, D. T. (2002). Experimental and quasi-experimental designs for generalized causal inference. Houghton Mifflin.

Further Reading and Research

Recommended Articles

• Experimental Design in Psychology: 3 Types With Examples
• Validity in Psychology: Types, Assessment and Improvement
• Statistical Significance, P-Values, Errors and Effect Sizes

Suggested Books

• Coolican, H. (2019). Research Methods and Statistics in Psychology (7th ed.). Routledge.
  • The standard research methods textbook for A level and undergraduate psychology, with detailed chapters on experiments, validity and the strengths and weaknesses of each type.
• Shadish, W. R., Cook, T. D., & Campbell, D. T. (2002). Experimental and Quasi-Experimental Designs for Generalized Causal Inference. Houghton Mifflin.
  • The classic advanced text on experiments without random assignment, explaining the threats to validity they face and the designs that reduce them.
• Milgram, S. (1974). Obedience to Authority: An Experimental View. Harper & Row.
  • Milgram's own account of his obedience research, including the variations such as the Bridgeport office, which show how changing the setting changes behaviour.

Recommended Websites

• AQA A-level Psychology (7182)
  • The official specification, past papers and mark schemes, including the research methods content on types of experiment.
• The Nobel Prize: Economic Sciences 2021
  • Accessible and advanced explanations of how natural experiments are used to answer questions about cause and effect.
• British Psychological Society Research Digest
  • Short, readable summaries of new psychology studies, useful for spotting how different types of experiment are used in current research.

Kathy Brodie

Kathy Brodie is an Early Years Professional, Trainer and Author of multiple books on Early Years Education and Child Development. She is the founder of Early Years TV and the Early Years Summit.

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To cite this article please use:

Early Years TV Types of Experiment in Psychology: Lab, Field, Natural, Quasi. Available at: https://www.earlyyears.tv/types-of-experiment-psychology-lab-field-natural-quasi/ (Accessed: 2 October 2026).