experimental method examples psychology

Experimental Psychology: 10 Examples & Definition

Dave Cornell (PhD)

Dr. Cornell has worked in education for more than 20 years. His work has involved designing teacher certification for Trinity College in London and in-service training for state governments in the United States. He has trained kindergarten teachers in 8 countries and helped businessmen and women open baby centers and kindergartens in 3 countries.

Learn about our Editorial Process

Chris Drew (PhD)

This article was peer-reviewed and edited by Chris Drew (PhD). The review process on Helpful Professor involves having a PhD level expert fact check, edit, and contribute to articles. Reviewers ensure all content reflects expert academic consensus and is backed up with reference to academic studies. Dr. Drew has published over 20 academic articles in scholarly journals. He is the former editor of the Journal of Learning Development in Higher Education and holds a PhD in Education from ACU.

Experimental psychology refers to studying psychological phenomena using scientific methods. Originally, the primary scientific method involved manipulating one variable and observing systematic changes in another variable.

Today, psychologists utilize several types of scientific methodologies.

Experimental psychology examines a wide range of psychological phenomena, including: memory, sensation and perception, cognitive processes, motivation, emotion, developmental processes, in addition to the neurophysiological concomitants of each of these subjects.

Studies are conducted on both animal and human participants, and must comply with stringent requirements and controls regarding the ethical treatment of both.

Definition of Experimental Psychology

Experimental psychology is a branch of psychology that utilizes scientific methods to investigate the mind and behavior.

It involves the systematic and controlled study of human and animal behavior through observation and experimentation .

Experimental psychologists design and conduct experiments to understand cognitive processes, perception, learning, memory, emotion, and many other aspects of psychology. They often manipulate variables ( independent variables ) to see how this affects behavior or mental processes (dependent variables).

The findings from experimental psychology research are often used to better understand human behavior and can be applied in a range of contexts, such as education, health, business, and more.

Experimental Psychology Examples

1. The Puzzle Box Studies (Thorndike, 1898) Placing different cats in a box that can only be escaped by pulling a cord, and then taking detailed notes on how long it took for them to escape allowed Edward Thorndike to derive the Law of Effect: actions followed by positive consequences are more likely to occur again, and actions followed by negative consequences are less likely to occur again (Thorndike, 1898).

2. Reinforcement Schedules (Skinner, 1956) By placing rats in a Skinner Box and changing when and how often the rats are rewarded for pressing a lever, it is possible to identify how each schedule results in different behavior patterns (Skinner, 1956). This led to a wide range of theoretical ideas around how rewards and consequences can shape the behaviors of both animals and humans.

3. Observational Learning (Bandura, 1980) Some children watch a video of an adult punching and kicking a Bobo doll. Other children watch a video in which the adult plays nicely with the doll. By carefully observing the children’s behavior later when in a room with a Bobo doll, researchers can determine if television violence affects children’s behavior (Bandura, 1980).

4. The Fallibility of Memory (Loftus & Palmer, 1974) A group of participants watch the same video of two cars having an accident. Two weeks later, some are asked to estimate the rate of speed the cars were going when they “smashed” into each other. Some participants are asked to estimate the rate of speed the cars were going when they “bumped” into each other. Changing the phrasing of the question changes the memory of the eyewitness.

5. Intrinsic Motivation in the Classroom (Dweck, 1990) To investigate the role of autonomy on intrinsic motivation, half of the students are told they are “free to choose” which tasks to complete. The other half of the students are told they “must choose” some of the tasks. Researchers then carefully observe how long the students engage in the tasks and later ask them some questions about if they enjoyed doing the tasks or not.

6. Systematic Desensitization (Wolpe, 1958) A clinical psychologist carefully documents his treatment of a patient’s social phobia with progressive relaxation. At first, the patient is trained to monitor, tense, and relax various muscle groups while viewing photos of parties. Weeks later, they approach a stranger to ask for directions, initiate a conversation on a crowded bus, and attend a small social gathering. The therapist’s notes are transcribed into a scientific report and published in a peer-reviewed journal.

7. Study of Remembering (Bartlett, 1932) Bartlett’s work is a seminal study in the field of memory, where he used the concept of “schema” to describe an organized pattern of thought or behavior. He conducted a series of experiments using folk tales to show that memory recall is influenced by cultural schemas and personal experiences.

8. Study of Obedience (Milgram, 1963) This famous study explored the conflict between obedience to authority and personal conscience. Milgram found that a majority of participants were willing to administer what they believed were harmful electric shocks to a stranger when instructed by an authority figure, highlighting the power of authority and situational factors in driving behavior.

9. Pavlov’s Dog Study (Pavlov, 1927) Ivan Pavlov, a Russian physiologist, conducted a series of experiments that became a cornerstone in the field of experimental psychology. Pavlov noticed that dogs would salivate when they saw food. He then began to ring a bell each time he presented the food to the dogs. After a while, the dogs began to salivate merely at the sound of the bell. This experiment demonstrated the principle of “classical conditioning.”

10, Piaget’s Stages of Development (Piaget, 1958) Jean Piaget proposed a theory of cognitive development in children that consists of four distinct stages: the sensorimotor stage (birth to 2 years), where children learn about the world through their senses and motor activities, through to the the formal operational stage (12 years and beyond), where abstract reasoning and hypothetical thinking develop. Piaget’s theory is an example of experimental psychology as it was developed through systematic observation and experimentation on children’s problem-solving behaviors .

Types of Research Methodologies in Experimental Psychology 

Researchers utilize several different types of research methodologies since the early days of Wundt (1832-1920).

1. The Experiment

The experiment involves the researcher manipulating the level of one variable, called the Independent Variable (IV), and then observing changes in another variable, called the Dependent Variable (DV).

The researcher is interested in determining if the IV causes changes in the DV. For example, does television violence make children more aggressive?

So, some children in the study, called research participants, will watch a show with TV violence, called the treatment group. Others will watch a show with no TV violence, called the control group.

So, there are two levels of the IV: violence and no violence. Next, children will be observed to see if they act more aggressively. This is the DV.

If TV violence makes children more aggressive, then the children that watched the violent show will me more aggressive than the children that watched the non-violent show.

A key requirement of the experiment is random assignment . Each research participant is assigned to one of the two groups in a way that makes it a completely random process. This means that each group will have a mix of children: different personality types, diverse family backgrounds, and range of intelligence levels.

2. The Longitudinal Study

A longitudinal study involves selecting a sample of participants and then following them for years, or decades, periodically collecting data on the variables of interest.

For example, a researcher might be interested in determining if parenting style affects academic performance of children. Parenting style is called the predictor variable , and academic performance is called the outcome variable .

Researchers will begin by randomly selecting a group of children to be in the study. Then, they will identify the type of parenting practices used when the children are 4 and 5 years old.

A few years later, perhaps when the children are 8 and 9, the researchers will collect data on their grades. This process can be repeated over the next 10 years, including through college.

If parenting style has an effect on academic performance, then the researchers will see a connection between the predictor variable and outcome variable.

Children raised with parenting style X will have higher grades than children raised with parenting style Y.

3. The Case Study

The case study is an in-depth study of one individual. This is a research methodology often used early in the examination of a psychological phenomenon or therapeutic treatment.

For example, in the early days of treating phobias, a clinical psychologist may try teaching one of their patients how to relax every time they see the object that creates so much fear and anxiety, such as a large spider.

The therapist would take very detailed notes on how the teaching process was implemented and the reactions of the patient. When the treatment had been completed, those notes would be written in a scientific form and submitted for publication in a scientific journal for other therapists to learn from.

There are several other types of methodologies available which vary different aspects of the three described above. The researcher will select a methodology that is most appropriate to the phenomenon they want to examine.

They also must take into account various practical considerations such as how much time and resources are needed to complete the study. Conducting research always costs money.

People and equipment are needed to carry-out every study, so researchers often try to obtain funding from their university or a government agency. 

Origins and Key Developments in Experimental Psychology

Wilhelm Maximilian Wundt (1832-1920) is considered one of the fathers of modern psychology. He was a physiologist and philosopher and helped establish psychology as a distinct discipline (Khaleefa, 1999).  

In 1879 he established the world’s first psychology research lab at the University of Leipzig. This is considered a key milestone for establishing psychology as a scientific discipline. In addition to being the first person to use the term “psychologist,” to describe himself, he also founded the discipline’s first scientific journal Philosphische Studien in 1883.

Another notable figure in the development of experimental psychology is Ernest Weber . Trained as a physician, Weber studied sensation and perception and created the first quantitative law in psychology.

The equation denotes how judgments of sensory differences are relative to previous levels of sensation, referred to as the just-noticeable difference (jnd). This is known today as Weber’s Law (Hergenhahn, 2009).    

Gustav Fechner , one of Weber’s students, published the first book on experimental psychology in 1860, titled Elemente der Psychophysik. His worked centered on the measurement of psychophysical facets of sensation and perception, with many of his methods still in use today.    

The first American textbook on experimental psychology was Elements of Physiological Psychology, published in 1887 by George Trumball Ladd .

Ladd also established a psychology lab at Yale University, while Stanley Hall and Charles Sanders continued Wundt’s work at a lab at Johns Hopkins University.

In the late 1800s, Charles Pierce’s contribution to experimental psychology is especially noteworthy because he invented the concept of random assignment (Stigler, 1992; Dehue, 1997).

Go Deeper: 15 Random Assignment Examples

This procedure ensures that each participant has an equal chance of being placed in any of the experimental groups (e.g., treatment or control group). This eliminates the influence of confounding factors related to inherent characteristics of the participants.

Random assignment is a fundamental criterion for a study to be considered a valid experiment.

From there, experimental psychology flourished in the 20th century as a science and transformed into an approach utilized in cognitive psychology, developmental psychology, and social psychology .

Today, the term experimental psychology refers to the study of a wide range of phenomena and involves methodologies not limited to the manipulation of variables.

The Scientific Process and Experimental Psychology

The one thing that makes psychology a science and distinguishes it from its roots in philosophy is the reliance upon the scientific process to answer questions. This makes psychology a science was the main goal of its earliest founders such as Wilhelm Wundt.

There are numerous steps in the scientific process, outlined in the graphic below.

1. Observation

First, the scientist observes an interesting phenomenon that sparks a question. For example, are the memories of eyewitnesses really reliable, or are they subject to bias or unintentional manipulation?

2. Hypothesize

Next, this question is converted into a testable hypothesis. For instance: the words used to question a witness can influence what they think they remember.

3. Devise a Study

Then the researcher(s) select a methodology that will allow them to test that hypothesis. In this case, the researchers choose the experiment, which will involve randomly assigning some participants to different conditions.

In one condition, participants are asked a question that implies a certain memory (treatment group), while other participants are asked a question which is phrased neutrally and does not imply a certain memory (control group).

The researchers then write a proposal that describes in detail the procedures they want to use, how participants will be selected, and the safeguards they will employ to ensure the rights of the participants.

That proposal is submitted to an Institutional Review Board (IRB). The IRB is comprised of a panel of researchers, community representatives, and other professionals that are responsible for reviewing all studies involving human participants.

4. Conduct the Study

If the IRB accepts the proposal, then the researchers may begin collecting data. After the data has been collected, it is analyzed using a software program such as SPSS.

Those analyses will either support or reject the hypothesis. That is, either the participants’ memories were affected by the wording of the question, or not.

5. Publish the study

Finally, the researchers write a paper detailing their procedures and results of the statistical analyses. That paper is then submitted to a scientific journal.

The lead editor of that journal will then send copies of the paper to 3-5 experts in that subject. Each of those experts will read the paper and basically try to find as many things wrong with it as possible. Because they are experts, they are very good at this task.

After reading those critiques, most likely, the editor will send the paper back to the researchers and require that they respond to the criticisms, collect more data, or reject the paper outright.

In some cases, the study was so well-done that the criticisms were minimal and the editor accepts the paper. It then gets published in the scientific journal several months later.

That entire process can easily take 2 years, usually more. But, the findings of that study went through a very rigorous process. This means that we can have substantial confidence that the conclusions of the study are valid.

Experimental psychology refers to utilizing a scientific process to investigate psychological phenomenon.

There are a variety of methods employed today. They are used to study a wide range of subjects, including memory, cognitive processes, emotions and the neurophysiological basis of each.

The history of psychology as a science began in the 1800s primarily in Germany. As interest grew, the field expanded to the United States where several influential research labs were established.

As more methodologies were developed, the field of psychology as a science evolved into a prolific scientific discipline that has provided invaluable insights into human behavior.

Bartlett, F. C., & Bartlett, F. C. (1995).  Remembering: A study in experimental and social psychology . Cambridge university press.

Dehue, T. (1997). Deception, efficiency, and random groups: Psychology and the gradual origination of the random group design. Isis , 88 (4), 653-673.

Ebbinghaus, H. (2013). Memory: A contribution to experimental psychology.  Annals of neurosciences ,  20 (4), 155.

Hergenhahn, B. R. (2009). An introduction to the history of psychology. Belmont. CA: Wadsworth Cengage Learning .

Khaleefa, O. (1999). Who is the founder of psychophysics and experimental psychology? American Journal of Islam and Society , 16 (2), 1-26.

Loftus, E. F., & Palmer, J. C. (1974).  Reconstruction of auto-mobile destruction : An example of the interaction between language and memory.  Journal of Verbal Learning and Verbal behavior , 13, 585-589.

Pavlov, I.P. (1927). Conditioned reflexes . Dover, New York.

Piaget, J. (1959).  The language and thought of the child  (Vol. 5). Psychology Press.

Piaget, J., Fraisse, P., & Reuchlin, M. (2014). Experimental psychology its scope and method: Volume I (Psychology Revivals): History and method . Psychology Press.

Skinner, B. F. (1956). A case history in scientlfic method. American Psychologist, 11 , 221-233

Stigler, S. M. (1992). A historical view of statistical concepts in psychology and educational research. American Journal of Education , 101 (1), 60-70.

Thorndike, E. L. (1898). Animal intelligence: An experimental study of the associative processes in animals. Psychological Review Monograph Supplement 2 .

Wolpe, J. (1958). Psychotherapy by reciprocal inhibition. Stanford, CA: Stanford University Press.

Appendix: Images reproduced as Text

Definition: Experimental psychology is a branch of psychology that focuses on conducting systematic and controlled experiments to study human behavior and cognition.

Overview: Experimental psychology aims to gather empirical evidence and explore cause-and-effect relationships between variables. Experimental psychologists utilize various research methods, including laboratory experiments, surveys, and observations, to investigate topics such as perception, memory, learning, motivation, and social behavior .

Example: The Pavlov’s Dog experimental psychology experiment used scientific methods to develop a theory about how learning and association occur in animals. The same concepts were subsequently used in the study of humans, wherein psychology-based ideas about learning were developed. Pavlov’s use of the empirical evidence was foundational to the study’s success.

Experimental Psychology Milestones:

1890: William James publishes “The Principles of Psychology”, a foundational text in the field of psychology.

1896: Lightner Witmer opens the first psychological clinic at the University of Pennsylvania, marking the beginning of clinical psychology.

1913: John B. Watson publishes “Psychology as the Behaviorist Views It”, marking the beginning of Behaviorism.

1920: Hermann Rorschach introduces the Rorschach inkblot test.

1938: B.F. Skinner introduces the concept of operant conditioning .

1967: Ulric Neisser publishes “Cognitive Psychology” , marking the beginning of the cognitive revolution.

1980: The third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) is published, introducing a new classification system for mental disorders.

The Scientific Process

• Observe an interesting phenomenon
• Formulate testable hypothesis
• Select methodology and design study
• Submit research proposal to IRB
• Collect and analyzed data; write paper
• Submit paper for critical reviews

• Dave Cornell (PhD) https://helpfulprofessor.com/author/dave-cornell-phd/ 23 Achieved Status Examples
• Dave Cornell (PhD) https://helpfulprofessor.com/author/dave-cornell-phd/ 25 Defense Mechanisms Examples
• Dave Cornell (PhD) https://helpfulprofessor.com/author/dave-cornell-phd/ 15 Theory of Planned Behavior Examples
• Dave Cornell (PhD) https://helpfulprofessor.com/author/dave-cornell-phd/ 18 Adaptive Behavior Examples

• Chris Drew (PhD) https://helpfulprofessor.com/author/chris-drew-phd/ 23 Achieved Status Examples
• Chris Drew (PhD) https://helpfulprofessor.com/author/chris-drew-phd/ 15 Ableism Examples
• Chris Drew (PhD) https://helpfulprofessor.com/author/chris-drew-phd/ 25 Defense Mechanisms Examples
• Chris Drew (PhD) https://helpfulprofessor.com/author/chris-drew-phd/ 15 Theory of Planned Behavior Examples

Leave a Comment Cancel Reply

Your email address will not be published. Required fields are marked *

Experimental Methods In Psychology

March 7, 2021 - paper 2 psychology in context | research methods.

There are three experimental methods in the field of psychology; Laboratory, Field and Natural Experiments. Each of the experimental methods holds different characteristics in relation to; the manipulation of the IV, the control of the EVs and the ability to accurately replicate the study in exactly the same way.

When conducting research, it is important to create an aim and a hypothesis,  click here  to learn more about the formation of aims and hypotheses.

We're not around right now. But you can send us an email and we'll get back to you, asap.

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.

• History & Society
• Science & Tech
• Biographies
• Animals & Nature
• Geography & Travel
• Arts & Culture
• Games & Quizzes
• On This Day
• One Good Fact
• New Articles
• Lifestyles & Social Issues
• Philosophy & Religion
• Politics, Law & Government
• World History
• Health & Medicine
• Browse Biographies
• Birds, Reptiles & Other Vertebrates
• Bugs, Mollusks & Other Invertebrates
• Environment
• Fossils & Geologic Time
• Entertainment & Pop Culture
• Sports & Recreation
• Visual Arts
• Demystified
• Image Galleries
• Infographics
• Top Questions
• Britannica Kids
• Saving Earth
• Space Next 50
• Student Center

experimental psychology

Our editors will review what you’ve submitted and determine whether to revise the article.

• American Psychological Association - Understanding Experimental Psychology

experimental psychology , a method of studying psychological phenomena and processes. The experimental method in psychology attempts to account for the activities of animals (including humans) and the functional organization of mental processes by manipulating variables that may give rise to behaviour; it is primarily concerned with discovering laws that describe manipulable relationships. The term generally connotes all areas of psychology that use the experimental method.

These areas include the study of sensation and perception , learning and memory , motivation , and biological psychology . There are experimental branches in many other areas, however, including child psychology , clinical psychology , educational psychology , and social psychology . Usually the experimental psychologist deals with normal, intact organisms; in biological psychology, however, studies are often conducted with organisms modified by surgery, radiation, drug treatment, or long-standing deprivations of various kinds or with organisms that naturally present organic abnormalities or emotional disorders. See also psychophysics .

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

6.1 Experiment Basics

Learning objectives.

• Explain what an experiment is and recognize examples of studies that are experiments and studies that are not experiments.
• Explain what internal validity is and why experiments are considered to be high in internal validity.
• Explain what external validity is and evaluate studies in terms of their external validity.
• Distinguish between the manipulation of the independent variable and control of extraneous variables and explain the importance of each.
• Recognize examples of confounding variables and explain how they affect the internal validity of a study.

What Is an Experiment?

As we saw earlier in the book, an experiment is a type of study designed specifically to answer the question of whether there is a causal relationship between two variables. Do changes in an independent variable cause changes in a dependent variable? Experiments have two fundamental features. The first is that the researchers manipulate, or systematically vary, the level of the independent variable. The different levels of the independent variable are called conditions. For example, in Darley and Latané’s experiment, the independent variable was the number of witnesses that participants believed to be present. The researchers manipulated this independent variable by telling participants that there were either one, two, or five other students involved in the discussion, thereby creating three conditions. The second fundamental feature of an experiment is that the researcher controls, or minimizes the variability in, variables other than the independent and dependent variable. These other variables are called extraneous variables. Darley and Latané tested all their participants in the same room, exposed them to the same emergency situation, and so on. They also randomly assigned their participants to conditions so that the three groups would be similar to each other to begin with. Notice that although the words manipulation and control have similar meanings in everyday language, researchers make a clear distinction between them. They manipulate the independent variable by systematically changing its levels and control other variables by holding them constant.

Internal and External Validity

Internal validity.

Recall that the fact that two variables are statistically related does not necessarily mean that one causes the other. “Correlation does not imply causation.” For example, if it were the case that people who exercise regularly are happier than people who do not exercise regularly, this would not necessarily mean that exercising increases people’s happiness. It could mean instead that greater happiness causes people to exercise (the directionality problem) or that something like better physical health causes people to exercise and be happier (the third-variable problem).

The purpose of an experiment, however, is to show that two variables are statistically related and to do so in a way that supports the conclusion that the independent variable caused any observed differences in the dependent variable. The basic logic is this: If the researcher creates two or more highly similar conditions and then manipulates the independent variable to produce just one difference between them, then any later difference between the conditions must have been caused by the independent variable. For example, because the only difference between Darley and Latané’s conditions was the number of students that participants believed to be involved in the discussion, this must have been responsible for differences in helping between the conditions.

An empirical study is said to be high in internal validity if the way it was conducted supports the conclusion that the independent variable caused any observed differences in the dependent variable. Thus experiments are high in internal validity because the way they are conducted—with the manipulation of the independent variable and the control of extraneous variables—provides strong support for causal conclusions.

External Validity

At the same time, the way that experiments are conducted sometimes leads to a different kind of criticism. Specifically, the need to manipulate the independent variable and control extraneous variables means that experiments are often conducted under conditions that seem artificial or unlike “real life” (Stanovich, 2010). In many psychology experiments, the participants are all college undergraduates and come to a classroom or laboratory to fill out a series of paper-and-pencil questionnaires or to perform a carefully designed computerized task. Consider, for example, an experiment in which researcher Barbara Fredrickson and her colleagues had college students come to a laboratory on campus and complete a math test while wearing a swimsuit (Fredrickson, Roberts, Noll, Quinn, & Twenge, 1998). At first, this might seem silly. When will college students ever have to complete math tests in their swimsuits outside of this experiment?

The issue we are confronting is that of external validity. An empirical study is high in external validity if the way it was conducted supports generalizing the results to people and situations beyond those actually studied. As a general rule, studies are higher in external validity when the participants and the situation studied are similar to those that the researchers want to generalize to. Imagine, for example, that a group of researchers is interested in how shoppers in large grocery stores are affected by whether breakfast cereal is packaged in yellow or purple boxes. Their study would be high in external validity if they studied the decisions of ordinary people doing their weekly shopping in a real grocery store. If the shoppers bought much more cereal in purple boxes, the researchers would be fairly confident that this would be true for other shoppers in other stores. Their study would be relatively low in external validity, however, if they studied a sample of college students in a laboratory at a selective college who merely judged the appeal of various colors presented on a computer screen. If the students judged purple to be more appealing than yellow, the researchers would not be very confident that this is relevant to grocery shoppers’ cereal-buying decisions.

We should be careful, however, not to draw the blanket conclusion that experiments are low in external validity. One reason is that experiments need not seem artificial. Consider that Darley and Latané’s experiment provided a reasonably good simulation of a real emergency situation. Or consider field experiments that are conducted entirely outside the laboratory. In one such experiment, Robert Cialdini and his colleagues studied whether hotel guests choose to reuse their towels for a second day as opposed to having them washed as a way of conserving water and energy (Cialdini, 2005). These researchers manipulated the message on a card left in a large sample of hotel rooms. One version of the message emphasized showing respect for the environment, another emphasized that the hotel would donate a portion of their savings to an environmental cause, and a third emphasized that most hotel guests choose to reuse their towels. The result was that guests who received the message that most hotel guests choose to reuse their towels reused their own towels substantially more often than guests receiving either of the other two messages. Given the way they conducted their study, it seems very likely that their result would hold true for other guests in other hotels.

A second reason not to draw the blanket conclusion that experiments are low in external validity is that they are often conducted to learn about psychological processes that are likely to operate in a variety of people and situations. Let us return to the experiment by Fredrickson and colleagues. They found that the women in their study, but not the men, performed worse on the math test when they were wearing swimsuits. They argued that this was due to women’s greater tendency to objectify themselves—to think about themselves from the perspective of an outside observer—which diverts their attention away from other tasks. They argued, furthermore, that this process of self-objectification and its effect on attention is likely to operate in a variety of women and situations—even if none of them ever finds herself taking a math test in her swimsuit.

Manipulation of the Independent Variable

Again, to manipulate an independent variable means to change its level systematically so that different groups of participants are exposed to different levels of that variable, or the same group of participants is exposed to different levels at different times. For example, to see whether expressive writing affects people’s health, a researcher might instruct some participants to write about traumatic experiences and others to write about neutral experiences. The different levels of the independent variable are referred to as conditions , and researchers often give the conditions short descriptive names to make it easy to talk and write about them. In this case, the conditions might be called the “traumatic condition” and the “neutral condition.”

Notice that the manipulation of an independent variable must involve the active intervention of the researcher. Comparing groups of people who differ on the independent variable before the study begins is not the same as manipulating that variable. For example, a researcher who compares the health of people who already keep a journal with the health of people who do not keep a journal has not manipulated this variable and therefore not conducted an experiment. This is important because groups that already differ in one way at the beginning of a study are likely to differ in other ways too. For example, people who choose to keep journals might also be more conscientious, more introverted, or less stressed than people who do not. Therefore, any observed difference between the two groups in terms of their health might have been caused by whether or not they keep a journal, or it might have been caused by any of the other differences between people who do and do not keep journals. Thus the active manipulation of the independent variable is crucial for eliminating the third-variable problem.

Of course, there are many situations in which the independent variable cannot be manipulated for practical or ethical reasons and therefore an experiment is not possible. For example, whether or not people have a significant early illness experience cannot be manipulated, making it impossible to do an experiment on the effect of early illness experiences on the development of hypochondriasis. This does not mean it is impossible to study the relationship between early illness experiences and hypochondriasis—only that it must be done using nonexperimental approaches. We will discuss this in detail later in the book.

In many experiments, the independent variable is a construct that can only be manipulated indirectly. For example, a researcher might try to manipulate participants’ stress levels indirectly by telling some of them that they have five minutes to prepare a short speech that they will then have to give to an audience of other participants. In such situations, researchers often include a manipulation check in their procedure. A manipulation check is a separate measure of the construct the researcher is trying to manipulate. For example, researchers trying to manipulate participants’ stress levels might give them a paper-and-pencil stress questionnaire or take their blood pressure—perhaps right after the manipulation or at the end of the procedure—to verify that they successfully manipulated this variable.

Control of Extraneous Variables

An extraneous variable is anything that varies in the context of a study other than the independent and dependent variables. In an experiment on the effect of expressive writing on health, for example, extraneous variables would include participant variables (individual differences) such as their writing ability, their diet, and their shoe size. They would also include situation or task variables such as the time of day when participants write, whether they write by hand or on a computer, and the weather. Extraneous variables pose a problem because many of them are likely to have some effect on the dependent variable. For example, participants’ health will be affected by many things other than whether or not they engage in expressive writing. This can make it difficult to separate the effect of the independent variable from the effects of the extraneous variables, which is why it is important to control extraneous variables by holding them constant.

Extraneous Variables as “Noise”

Extraneous variables make it difficult to detect the effect of the independent variable in two ways. One is by adding variability or “noise” to the data. Imagine a simple experiment on the effect of mood (happy vs. sad) on the number of happy childhood events people are able to recall. Participants are put into a negative or positive mood (by showing them a happy or sad video clip) and then asked to recall as many happy childhood events as they can. The two leftmost columns of Table 6.1 “Hypothetical Noiseless Data and Realistic Noisy Data” show what the data might look like if there were no extraneous variables and the number of happy childhood events participants recalled was affected only by their moods. Every participant in the happy mood condition recalled exactly four happy childhood events, and every participant in the sad mood condition recalled exactly three. The effect of mood here is quite obvious. In reality, however, the data would probably look more like those in the two rightmost columns of Table 6.1 “Hypothetical Noiseless Data and Realistic Noisy Data” . Even in the happy mood condition, some participants would recall fewer happy memories because they have fewer to draw on, use less effective strategies, or are less motivated. And even in the sad mood condition, some participants would recall more happy childhood memories because they have more happy memories to draw on, they use more effective recall strategies, or they are more motivated. Although the mean difference between the two groups is the same as in the idealized data, this difference is much less obvious in the context of the greater variability in the data. Thus one reason researchers try to control extraneous variables is so their data look more like the idealized data in Table 6.1 “Hypothetical Noiseless Data and Realistic Noisy Data” , which makes the effect of the independent variable is easier to detect (although real data never look quite that good).

Table 6.1 Hypothetical Noiseless Data and Realistic Noisy Data

One way to control extraneous variables is to hold them constant. This can mean holding situation or task variables constant by testing all participants in the same location, giving them identical instructions, treating them in the same way, and so on. It can also mean holding participant variables constant. For example, many studies of language limit participants to right-handed people, who generally have their language areas isolated in their left cerebral hemispheres. Left-handed people are more likely to have their language areas isolated in their right cerebral hemispheres or distributed across both hemispheres, which can change the way they process language and thereby add noise to the data.

In principle, researchers can control extraneous variables by limiting participants to one very specific category of person, such as 20-year-old, straight, female, right-handed, sophomore psychology majors. The obvious downside to this approach is that it would lower the external validity of the study—in particular, the extent to which the results can be generalized beyond the people actually studied. For example, it might be unclear whether results obtained with a sample of younger straight women would apply to older gay men. In many situations, the advantages of a diverse sample outweigh the reduction in noise achieved by a homogeneous one.

Extraneous Variables as Confounding Variables

The second way that extraneous variables can make it difficult to detect the effect of the independent variable is by becoming confounding variables. A confounding variable is an extraneous variable that differs on average across levels of the independent variable. For example, in almost all experiments, participants’ intelligence quotients (IQs) will be an extraneous variable. But as long as there are participants with lower and higher IQs at each level of the independent variable so that the average IQ is roughly equal, then this variation is probably acceptable (and may even be desirable). What would be bad, however, would be for participants at one level of the independent variable to have substantially lower IQs on average and participants at another level to have substantially higher IQs on average. In this case, IQ would be a confounding variable.

To confound means to confuse, and this is exactly what confounding variables do. Because they differ across conditions—just like the independent variable—they provide an alternative explanation for any observed difference in the dependent variable. Figure 6.1 “Hypothetical Results From a Study on the Effect of Mood on Memory” shows the results of a hypothetical study, in which participants in a positive mood condition scored higher on a memory task than participants in a negative mood condition. But if IQ is a confounding variable—with participants in the positive mood condition having higher IQs on average than participants in the negative mood condition—then it is unclear whether it was the positive moods or the higher IQs that caused participants in the first condition to score higher. One way to avoid confounding variables is by holding extraneous variables constant. For example, one could prevent IQ from becoming a confounding variable by limiting participants only to those with IQs of exactly 100. But this approach is not always desirable for reasons we have already discussed. A second and much more general approach—random assignment to conditions—will be discussed in detail shortly.

Figure 6.1 Hypothetical Results From a Study on the Effect of Mood on Memory

Because IQ also differs across conditions, it is a confounding variable.

Key Takeaways

• An experiment is a type of empirical study that features the manipulation of an independent variable, the measurement of a dependent variable, and control of extraneous variables.
• Studies are high in internal validity to the extent that the way they are conducted supports the conclusion that the independent variable caused any observed differences in the dependent variable. Experiments are generally high in internal validity because of the manipulation of the independent variable and control of extraneous variables.
• Studies are high in external validity to the extent that the result can be generalized to people and situations beyond those actually studied. Although experiments can seem “artificial”—and low in external validity—it is important to consider whether the psychological processes under study are likely to operate in other people and situations.
• Practice: List five variables that can be manipulated by the researcher in an experiment. List five variables that cannot be manipulated by the researcher in an experiment.

Practice: For each of the following topics, decide whether that topic could be studied using an experimental research design and explain why or why not.

• Effect of parietal lobe damage on people’s ability to do basic arithmetic.
• Effect of being clinically depressed on the number of close friendships people have.
• Effect of group training on the social skills of teenagers with Asperger’s syndrome.
• Effect of paying people to take an IQ test on their performance on that test.

Cialdini, R. (2005, April). Don’t throw in the towel: Use social influence research. APS Observer . Retrieved from http://www.psychologicalscience.org/observer/getArticle.cfm?id=1762 .

Fredrickson, B. L., Roberts, T.-A., Noll, S. M., Quinn, D. M., & Twenge, J. M. (1998). The swimsuit becomes you: Sex differences in self-objectification, restrained eating, and math performance. Journal of Personality and Social Psychology, 75 , 269–284.

Stanovich, K. E. (2010). How to think straight about psychology (9th ed.). Boston, MA: Allyn & Bacon.

Research Methods in Psychology Copyright © 2016 by University of Minnesota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

Experimental Method

The experimental method.

Experiments are one of the most popular and useful research methods in psychology. The key types are laboratory and field experiments.

Role in psychology

• Experiments play a major role throughout psychology.
• As a method, experiments allow one variable to be manipulated while keeping everything the same.
• This allows researchers to show cause and effect.

Laboratory experiments

• Some experiments take place under controlled condition, such as in a university room supervised by the researchers.
• These are called laboratory (or ‘lab’) experiments.
• The advantage of laboratory experiments is that they increase the level of control that a researcher can have.
• But they reduce the level of ecological validity of the research.

Field experiments

• Other experiments take place in a participant’s natural surroundings, such as their school or workplace.
• These are called field experiments.
• The advantage of field experiments is that they increase the ecological validity of the study by making the surroundings more realistic.
• But they reduce the level of control.

True experiments

• Both field experiments and lab experiments control the variables under investigation, and randomly allocate participants to groups.
• These characteristics mean that they are true experiments.

Quasi-Experiments

Quasi-experiments are not true experiments because they lack control over the experimental groups used.

Lack of random allocation

• For example, if one of the variables under investigation is gender, people can’t be randomly allocated to ‘male’ and ‘female’ conditions.
• A study is termed a quasi-experiment if it lacks random allocation to groups but is like a true experiment in most or all other ways.

Examples of quasi-experiments

• Other examples of quasi-experiments include studies which compare different types of personality (e.g. introverts versus extroverts) or compare people who have a psychological disorder with a control group who do not.
• Such studies cannot randomly allocate people to groups.

Quasi vs lab

• Quasi-experiments could take place in a lab, and all other aspects of the research and data gathering can be controlled.
• This means they are easy to mix up with laboratory experiments.

Natural Experiments

Natural experiments are logically similar to true experiments, but the situation happens by itself and so is completely uncontrolled by the researcher.

• For example, it wouldn’t be ethically correct to expose people to a lot of stress to investigate its effects.
• In such situations, a researcher may use a natural experiment.

Similarity to true experiments

• For example, they could compare the educational outcomes of school pupils who experience a lot of stress versus those who do not.

Differences to true experiments

• In contrast to a true experiment or a quasi-experiment, the variable under investigation happens by itself and so is completely uncontrolled by the researcher.
• The researcher also has no control at all over who is in each ‘experimental’ group.

Location of natural experiments

• Because natural experiments are not set up by the researcher, they always take place in participants’ everyday surroundings such as their home or school.
• This means they are easy to mix up with field experiments.

1 Social Influence

1.1 Social Influence

1.1.1 Conformity

1.1.2 Asch (1951)

1.1.3 Sherif (1935)

1.1.4 Conformity to Social Roles

1.1.5 BBC Prison Study

1.1.6 End of Topic Test - Conformity

1.1.7 Obedience

1.1.8 Analysing Milgram's Experiment

1.1.9 Agentic State & Legitimate Authority

1.1.10 Variables of Obedience

1.1.11 Resistance to Social Influence

1.1.12 Minority Influence & Social Change

1.1.13 Minority Influence & Social Impact Theory

1.1.14 End of Topic Test - Social Influences

1.1.15 Exam-Style Question - Conformity

1.1.16 Top Grade AO2/AO3 - Social Influence

2.1.1 Multi-Store Model of Memory

2.1.2 Short-Term vs Long-Term Memory

2.1.3 Long-Term Memory

2.1.4 Support for the Multi-Store Model of Memory

2.1.5 Duration Studies

2.1.6 Capacity Studies

2.1.7 Coding Studies

2.1.8 The Working Memory Model

2.1.9 The Working Memory Model 2

2.1.10 Support for the Working Memory Model

2.1.11 Explanations for Forgetting

2.1.12 Studies on Interference

2.1.13 Cue-Dependent Forgetting

2.1.14 Eye Witness Testimony - Loftus & Palmer

2.1.15 Eye Witness Testimony Loftus

2.1.16 Eyewitness Testimony - Post-Event Discussion

2.1.17 Eyewitness Testimony - Age & Misleading Questions

2.1.18 Cognitive Interview

2.1.19 Cognitive Interview - Geiselman & Fisher

2.1.20 End of Topic Test - Memory

2.1.21 Exam-Style Question - Memory

2.1.22 A-A* (AO3/4) - Memory

3 Attachment

3.1 Attachment

3.1.1 Caregiver-Infant Interaction

3.1.2 Condon & Sander (1974)

3.1.3 Schaffer & Emerson (1964)

3.1.4 Multiple Attachments

3.1.5 Studies on the Role of the Father

3.1.6 Animal Studies of Attachment

3.1.7 Explanations of Attachment

3.1.8 Attachment Types - Strange Situation

3.1.9 Cultural Differences in Attachment

3.1.10 Disruption of Attachment

3.1.11 Disruption of Attachment - Privation

3.1.12 Overcoming the Effects of Disruption

3.1.13 The Effects of Institutionalisation

3.1.14 Early Attachment

3.1.15 Critical Period of Attachment

3.1.16 End of Topic Test - Attachment

3.1.17 Exam-Style Question - Attachment

3.1.18 Top Grade AO2/AO3 - Attachment

4 Psychopathology

4.1 Psychopathology

4.1.1 Definitions of Abnormality

4.1.2 Definitions of Abnormality 2

4.1.3 Phobias, Depression & OCD

4.1.4 Phobias: Behavioural Approach

4.1.5 Evaluation of Behavioural Explanations of Phobias

4.1.6 Depression: Cognitive Approach

4.1.7 OCD: Biological Approach

4.1.8 Evidence for the Biological Approach

4.1.9 End of Topic Test - Psychopathy

4.1.10 Exam-Style Question - Phobias

4.1.11 Top Grade AO2/AO3 - Psychopathology

5 Approaches in Psychology

5.1 Approaches in Psychology

5.1.1 Psychology as a Science

5.1.2 Origins of Psychology

5.1.3 Reductionism & Problems with Introspection

5.1.4 The Behaviourist Approach - Classical Conditioning

5.1.5 Pavlov's Experiment

5.1.6 Little Albert Study

5.1.7 The Behaviourist Approach - Operant Conditioning

5.1.8 Social Learning Theory

5.1.9 The Cognitive Approach 1

5.1.10 The Cognitive Approach 2

5.1.11 The Biological Approach

5.1.12 Gottesman (1991) - Twin Studies

5.1.13 Brain Scanning

5.1.14 Structure of Personality & Little Hans

5.1.15 The Psychodynamic Approach (A2 only)

5.1.16 Humanistic Psychology (A2 only)

5.1.17 Aronoff (1957) (A2 Only)

5.1.18 Rogers' Client-Centred Therapy (A2 only)

5.1.19 End of Topic Test - Approaches in Psychology

5.1.20 Exam-Style Question - Approaches in Psychology

5.2 Comparison of Approaches (A2 only)

5.2.1 Psychodynamic Approach

5.2.2 Cognitive Approach

5.2.3 Biological Approach

5.2.4 Behavioural Approach

5.2.5 End of Topic Test - Comparison of Approaches

6 Biopsychology

6.1 Biopsychology

6.1.1 Nervous System Divisions

6.1.2 Neuron Structure & Function

6.1.3 Neurotransmitters

6.1.4 Endocrine System Function

6.1.5 Fight or Flight Response

6.1.6 The Brain (A2 only)

6.1.7 Localisation of Brain Function (A2 only)

6.1.8 Studying the Brain (A2 only)

6.1.9 CIMT (A2 Only) & Postmortem Examinations

6.1.10 Biological Rhythms (A2 only)

6.1.11 Studies on Biological Rhythms (A2 Only)

6.1.12 End of Topic Test - Biopsychology

6.1.13 Top Grade AO2/AO3 - Biopsychology

7 Research Methods

7.1 Research Methods

7.1.1 Experimental Method

7.1.2 Observational Techniques

7.1.3 Covert, Overt & Controlled Observation

7.1.4 Self-Report Techniques

7.1.5 Correlations

7.1.6 Exam-Style Question - Research Methods

7.1.7 End of Topic Test - Research Methods

7.2 Scientific Processes

7.2.1 Aims, Hypotheses & Sampling

7.2.2 Pilot Studies & Design

7.2.3 Questionnaires

7.2.4 Variables & Control

7.2.5 Demand Characteristics & Investigator Effects

7.2.6 Ethics

7.2.7 Limitations of Ethical Guidelines

7.2.8 Consent & Protection from Harm Studies

7.2.9 Peer Review & The Economy

7.2.10 Validity (A2 only)

7.2.11 Reliability (A2 only)

7.2.12 Features of Science (A2 only)

7.2.13 Paradigms & Falsifiability (A2 only)

7.2.14 Scientific Report (A2 only)

7.2.15 Scientific Report 2 (A2 only)

7.2.16 End of Topic Test - Scientific Processes

7.3 Data Handling & Analysis

7.3.1 Types of Data

7.3.2 Descriptive Statistics

7.3.3 Correlation

7.3.4 Evaluation of Descriptive Statistics

7.3.5 Presentation & Display of Data

7.3.6 Levels of Measurement (A2 only)

7.3.7 Content Analysis (A2 only)

7.3.8 Case Studies (A2 only)

7.3.9 Thematic Analysis (A2 only)

7.3.10 End of Topic Test - Data Handling & Analysis

7.4 Inferential Testing

7.4.1 Introduction to Inferential Testing

7.4.2 Sign Test

7.4.3 Piaget Conservation Experiment

7.4.4 Non-Parametric Tests

8 Issues & Debates in Psychology (A2 only)

8.1 Issues & Debates in Psychology (A2 only)

8.1.1 Culture Bias

8.1.2 Sub-Culture Bias

8.1.3 Gender Bias

8.1.4 Ethnocentrism

8.1.5 Cross Cultural Research

8.1.6 Free Will & Determinism

8.1.7 Comparison of Free Will & Determinism

8.1.8 Reductionism & Holism

8.1.9 Reductionist & Holistic Approaches

8.1.10 Nature-Nurture Debate

8.1.11 Interactionist Approach

8.1.12 Nature-Nurture Methods

8.1.13 Nature-Nurture Approaches

8.1.14 Idiographic & Nomothetic Approaches

8.1.15 Socially Sensitive Research

8.1.16 End of Topic Test - Issues and Debates

9 Option 1: Relationships (A2 only)

9.1 Relationships: Sexual Relationships (A2 only)

9.1.1 Sexual Selection & Human Reproductive Behaviour

9.1.2 Intersexual & Intrasexual Selection

9.1.3 Evaluation of Sexual Selection Behaviour

9.1.4 Factors Affecting Attraction: Self-Disclosure

9.1.5 Evaluation of Self-Disclosure Theory

9.1.6 Self Disclosure in Computer Communication

9.1.7 Factors Affecting Attraction: Physical Attributes

9.1.8 Matching Hypothesis Studies

9.1.9 Factors Affecting Physical Attraction

9.1.10 Factors Affecting Attraction: Filter Theory 1

9.1.11 Factors Affecting Attraction: Filter Theory 2

9.1.12 Evaluation of Filter Theory

9.1.13 End of Topic Test - Sexual Relationships

9.2 Relationships: Romantic Relationships (A2 only)

9.2.1 Social Exchange Theory

9.2.2 Evaluation of Social Exchange Theory

9.2.3 Equity Theory

9.2.4 Evaluation of Equity Theory

9.2.5 Rusbult’s Investment Model

9.2.6 Evaluation of Rusbult's Investment Model

9.2.7 Relationship Breakdown

9.2.8 Studies on Relationship Breakdown

9.2.9 Evaluation of Relationship Breakdown

9.2.10 End of Topic Test - Romantic relationships

9.3 Relationships: Virtual & Parasocial (A2 only)

9.3.1 Virtual Relationships in Social Media

9.3.2 Evaluation of Reduced Cues & Hyperpersonal

9.3.3 Parasocial Relationships

9.3.4 Attachment Theory & Parasocial Relationships

9.3.5 Evaluation of Parasocial Relationship Theories

9.3.6 End of Topic Test - Virtual & Parasocial Realtions

10 Option 1: Gender (A2 only)

10.1 Gender (A2 only)

10.1.1 Sex, Gender & Androgyny

10.1.2 Gender Identity Disorder

10.1.3 Biological & Social Explanations of GID

10.1.4 Biological Influences on Gender

10.1.5 Effects of Hormones on Gender

10.1.6 End of Topic Test - Gender 1

10.1.7 Kohlberg’s Theory of Gender Constancy

10.1.8 Evaluation of Kohlberg's Theory

10.1.9 Gender Schema Theory

10.1.10 Psychodynamic Approach to Gender Development 1

10.1.11 Psychodynamic Approach to Gender Development 2

10.1.12 Social Approach to Gender Development

10.1.13 Criticisms of Social Theory

10.1.14 End of Topic Test - Gender 2

10.1.15 Media Influence on Gender Development

10.1.16 Cross Cultural Research

10.1.17 Childcare & Gender Roles

10.1.18 End of Topic Test - Gender 3

11 Option 1: Cognition & Development (A2 only)

11.1 Cognition & Development (A2 only)

11.1.1 Piaget’s Theory of Cognitive Development 1

11.1.2 Piaget's Theory of Cognitive Development 2

11.1.3 Schema Accommodation Assimilation & Equilibration

11.1.4 Piaget & Inhelder’s Three Mountains Task (1956)

11.1.5 Conservation & Class Inclusion

11.1.6 Evaluation of Piaget

11.1.7 End of Topic Test - Cognition & Development 1

11.1.8 Vygotsky

11.1.9 Evaluation of Vygotsky

11.1.10 Baillargeon

11.1.11 Baillargeon's studies

11.1.12 Evaluation of Baillargeon

11.1.13 End of Topic Test - Cognition & Development 2

11.1.14 Sense of Self & Theory of Mind

11.1.15 Baron-Cohen Studies

11.1.16 Selman’s Five Levels of Perspective Taking

11.1.17 Biological Basis of Social Cognition

11.1.18 Evaluation of Biological Basis of Social Cognition

11.1.19 Important Issues in Social Neuroscience

11.1.20 End of Topic Test - Cognition & Development 3

11.1.21 Top Grade AO2/AO3 - Cognition & Development

12 Option 2: Schizophrenia (A2 only)

12.1 Schizophrenia: Diagnosis (A2 only)

12.1.1 Classification & Diagnosis

12.1.2 Reliability & Validity of Diagnosis

12.1.3 Gender & Cultural Bias

12.1.4 Pinto (2017) & Copeland (1971)

12.1.5 End of Topic Test - Scizophrenia Diagnosis

12.2 Schizophrenia: Treatment (A2 only)

12.2.1 Family-Based Psychological Explanations

12.2.2 Evaluation of Family-Based Explanations

12.2.3 Cognitive Explanations

12.2.4 Drug Therapies

12.2.5 Evaluation of Drug Therapies

12.2.6 Biological Explanations for Schizophrenia

12.2.7 Dopamine Hypothesis

12.2.8 End of Topic Test - Schizoprenia Treatment 1

12.2.9 Psychological Therapies 1

12.2.10 Psychological Therapies 2

12.2.11 Evaluation of Psychological Therapies

12.2.12 Interactionist Approach - Diathesis-Stress Model

12.2.13 Interactionist Approach - Triggers & Treatment

12.2.14 Evaluation of the Interactionist Approach

12.2.15 End of Topic Test - Scizophrenia Treatments 2

13 Option 2: Eating Behaviour (A2 only)

13.1 Eating Behaviour (A2 only)

13.1.1 Explanations for Food Preferences

13.1.2 Birch et al (1987) & Lowe et al (2004)

13.1.3 Control of Eating Behaviours

13.1.4 Control of Eating Behaviour: Leptin

13.1.5 Biological Explanations for Anorexia Nervosa

13.1.6 Psychological Explanations: Family Systems Theory

13.1.7 Psychological Explanations: Social Learning Theory

13.1.8 Psychological Explanations: Cognitive Theory

13.1.9 Biological Explanations for Obesity

13.1.10 Biological Explanations: Studies

13.1.11 Psychological Explanations for Obesity

13.1.12 Psychological Explanations: Studies

13.1.13 End of Topic Test - Eating Behaviour

14 Option 2: Stress (A2 only)

14.1 Stress (A2 only)

14.1.1 Physiology of Stress

14.1.2 Role of Stress in Illness

14.1.3 Role of Stress in Illness: Studies

14.1.4 Social Readjustment Rating Scales

14.1.5 Hassles & Uplifts Scales

14.1.6 Stress, Workload & Control

14.1.7 Stress Level Studies

14.1.8 End of Topic Test - Stress 1

14.1.9 Physiological Measures of Stress

14.1.10 Individual Differences

14.1.11 Stress & Gender

14.1.12 Drug Therapy & Biofeedback for Stress

14.1.13 Stress Inoculation Therapy

14.1.14 Social Support & Stress

14.1.15 End of Topic Test - Stress 2

15 Option 3: Aggression (A2 only)

15.1 Aggression: Physiological (A2 only)

15.1.1 Neural Mechanisms

15.1.2 Serotonin

15.1.3 Hormonal Mechanisms

15.1.4 Genetic Factors

15.1.5 Genetic Factors 2

15.1.6 End of Topic Test - Aggression: Physiological 1

15.1.7 Ethological Explanation

15.1.8 Innate Releasing Mechanisms & Fixed Action Pattern

15.1.9 Evolutionary Explanations

15.1.10 Buss et al (1992) - Sex Differences in Jealousy

15.1.11 Evaluation of Evolutionary Explanations

15.1.12 End of Topic Test - Aggression: Physiological 2

15.2 Aggression: Social Psychological (A2 only)

15.2.1 Social Psychological Explanation

15.2.2 Buss (1963) - Frustration/Aggression

15.2.3 Social Psychological Explanation 2

15.2.4 Social Learning Theory (SLT) 1

15.2.5 Social Learning Theory (SLT) 2

15.2.6 Limitations of Social Learning Theory (SLT)

15.2.7 Deindividuation

15.2.8 Deindividuation 2

15.2.9 Deindividuation - Diener et al (1976)

15.2.10 End of Topic Test - Aggression: Social Psychology

15.2.11 Institutional Aggression: Prisons

15.2.12 Evaluation of Dispositional & Situational

15.2.13 Influence of Computer Games

15.2.14 Influence of Television

15.2.15 Evaluation of Studies on Media

15.2.16 Desensitisation & Disinhibition

15.2.17 Cognitive Priming

15.2.18 End of Topic Test - Aggression: Social Psychology

16 Option 3: Forensic Psychology (A2 only)

16.1 Forensic Psychology (A2 only)

16.1.1 Defining Crime

16.1.2 Measuring Crime

16.1.3 Offender Profiling

16.1.4 Evaluation of Offender Profiling

16.1.5 John Duffy Case Study

16.1.6 Biological Explanations 1

16.1.7 Biological Explanations 2

16.1.8 Evaluation of the Biological Explanation

16.1.9 Cognitive Explanations

16.1.10 Moral Reasoning

16.1.11 Psychodynamic Explanation 1

16.1.12 Psychodynamic Explanation 2

16.1.13 End of Topic Test - Forensic Psychology 1

16.1.14 Differential Association Theory

16.1.15 Custodial Sentencing

16.1.16 Effects of Prison

16.1.17 Evaluation of the Effects of Prison

16.1.18 Recidivism

16.1.19 Behavioural Treatments & Therapies

16.1.20 Effectiveness of Behavioural Treatments

16.1.21 Restorative Justice

16.1.22 End of Topic Test - Forensic Psychology 2

17 Option 3: Addiction (A2 only)

17.1 Addiction (A2 only)

17.1.1 Definition

17.1.2 Brain Neurochemistry Explanation

17.1.3 Learning Theory Explanation

17.1.4 Evaluation of a Learning Theory Explanation

17.1.5 Cognitive Bias

17.1.6 Griffiths on Cognitive Bias

17.1.7 Evaluation of Cognitive Theory (A2 only)

17.1.8 End of Topic Test - Addiction 1

17.1.9 Gambling Addiction & Learning Theory

17.1.10 Social Influences on Addiction 1

17.1.11 Social Influences on Addiction 2

17.1.12 Personal Influences on Addiction

17.1.13 Genetic Explanations of Addiction

17.1.14 End of Topic Test - Addiction 2

17.2 Treating Addiction (A2 only)

17.2.1 Drug Therapy

17.2.2 Behavioural Interventions

17.2.3 Cognitive Behavioural Therapy

17.2.4 Theory of Reasoned Action

17.2.5 Theory of Planned Behaviour

17.2.6 Six Stage Model of Behaviour Change

17.2.7 End of Topic Test - Treating Addiction

Jump to other topics

Unlock your full potential with GoStudent tutoring

Affordable 1:1 tutoring from the comfort of your home

Tutors are matched to your specific learning needs

30+ school subjects covered

Top Grade AO2/AO3 - Biopsychology

Observational Techniques

Experimental Psychology Studies Humans and Animals

Understanding Experimental Psychology

Our personalities, and to some degree our life experiences, are defined by the way we behave. But what influences the way we behave in the first place? How does our behavior shape our experiences throughout our lives? 

Experimental psychologists are interested in exploring theoretical questions, often by creating a hypothesis and then setting out to prove or disprove it through experimentation. They study a wide range of behavioral topics among humans and animals, including sensation, perception, attention, memory, cognition and emotion.

Experimental Psychology Applied

Experimental psychologists use scientific methods to collect data and perform research. Often, their work builds, one study at a time, to a larger finding or conclusion. Some researchers have devoted their entire career to answering one complex research question. 

These psychologists work in a variety of settings, including universities, research centers, government agencies and private businesses. The focus of their research is as varied as the settings in which they work. Often, personal interest and educational background will influence the research questions they choose to explore. 

In a sense, all psychologists can be considered experimental psychologists since research is the foundation of the discipline, and many psychologists split their professional focus among research, patient care, teaching or program administration. Experimental psychologists, however, often devote their full attention to research — its design, execution, analysis and dissemination. 

Those focusing their careers specifically on experimental psychology contribute work across subfields . For example, they use scientific research to provide insights that improve teaching and learning, create safer workplaces and transportation systems, improve substance abuse treatment programs and promote healthy child development.

Related books

Deliberate Practice in Interpersonal Psychotherapy

APA Handbook of Health Psychology

Methodological Issues and Strategies, 5e

Essentials of Constructivist Critical Incident ...

How to Mix Methods

Psychology subfields

7 Important Methods in Psychology With Examples

Psychology is a scientific study of the human mind, mental processes, and behavior. It is called a scientific study because psychologists also do various systematic research and experiments to study and formulate psychological theories like other scientists. Psychological researches involve understanding complex mental processes, human behavior, and collecting different types of data (physiological, psychological, physical, and demographic data), psychologists use various research methods as it is difficult to obtain accurate and reliable results if we use a single research method for collecting research data. The type of method they use depends upon the type of research. Broadly, researches are divide into two types, i.e., experimental and non-experimental researches. Experimental researches involve two or more variables, and it studies the effect of the independent variable on the dependent variable (cause-effect relationship), whereas non-experimental researches do not involve the manipulations of variables. The concept of variables is briefly explained further in this article. Let’s get familiar with some widely used methods of collecting psychology research data.

1. Experimental Method

To understand the experimental method, firstly we need to be familiar with the term ‘variable.’ A variable is an event or stimulus that varies, and its values can be measured. It is to be noted that we can not regard any object as a variable; in fact, the attributes related to that object are called variables. For example, A person is not a variable, but the height of the person is a variable because different people may have different heights. In the experiment method of data collection, we mainly concern with two types of variables, i.e., independent variables and dependent variables. If the value of the variable is manipulated by the researcher to observe its effects, then it is called the independent variable, and the variable that is affected by the change in the independent variable is called the dependent variable. For example, if we want to study the influence of alcohol on the reaction time and driving abilities of the driver, then the amount of alcohol that the driver consumes is the independent variable, and the driving performance of the driver is called the dependent variable. Experimental methods are conducted to establish the relationship between the independent variable (cause) and dependent variables (effect). The experiments are conducted very carefully, and any variables other than the independent variable are kept constant or negligible so that an accurate relationship between the cause and effect can be established. In the above example, other factors like the driver’s stress, anxiety, or mood (extraneous variables) can interfere with the dependent variable (driving ability). It is difficult to avoid these extraneous variables; extraneous variables are the undesired variables that are not studied under the experiments, and their manipulation can alter the results of the study, but we should always try to make them constant or negligible for accurate results.

Control Group and Experimental Group

Experiments generally consist of several research groups that are broadly categorized into control groups and experimental groups. The group that undergoes the manipulation of the independent variable is called the experimental group, whereas the group that does not undergoes the independent variable manipulation, but its other factors or variables are kept the same as the experimental group, is called a control group. The control group basically acts as a comparison group as it is used to measure the changes caused by the independent variable on the experimental group. For example, if a researcher wants to study that how does the conduction of exams affects the learning ability of the student, then, here, the learning ability of the student is the dependent variable and exams are the independent variable. In this experiment, some lectures will be delivered to the students of the same class and of nearly the same learning abilities (based on their previous exam scores or other criteria), and then the students are divide into different groups, one group is not subjected to give the exams, while the other group has to give the exam of what they have learned in the lesson. The group of students that were not subjected to give the exams is called the control group, and the group of students that were subjected to give the exams is called the experimental group. The number of experimental groups can be more than one based on how often does the exams are conducted for each group. At the end of the experiments, the researcher can find the results by comparing the experimental group with the control group.

Types of Experimental Method

Some major types of the experimental method include,

1. Lab Experiments

It is difficult to conduct some experiments in natural settings as many extraneous variables can become a problem for the research. So, researchers conduct the experiments in a controlled manner in laboratories or research centers. It is easy to manage the independent and dependent variables in the controlled settings. For example, if the researcher wants to study the effect of different kinds of music like pop, classical, etc., on the health of the patients, then the researcher will conduct this study in a room rather than in a natural environment as it’s easy to keep extraneous variables constant in the closed settings. Here, music is the independent variable and health is the dependent variable. If the same experiment is conducted outside the lab, then extraneous variables like sunlight, weather, noise, etc., may interfere with the study and manipulate the results of the research.

2. Field Experiments

Sometimes, lab experiment results face criticism for their lack of generalizability as they are not conducted in real-life settings. Field experiments are conducted in the natural environment and real-life settings like schools, industries, hospitals, etc., so they are more ecologically valid than lab experiments. For example, if we want to study whether classroom learning or open environment learning is the best teaching method for students, the researcher would prefer the field experiment over the lab experiment. However, in field experiments, it is very difficult to control the undesired or extraneous variables, which makes it difficult to establish an accurate cause-effect relationship. Moreover, they consume more time than the lab experiments.

3. Quasi Experiments

In lab experiments or fields experiments, sometimes, it is difficult to manipulate some variables due to ethical issues or other constraints. Quasi-experiments are conducted in this situation. In quasi-experiments, the researcher studies that how does a single or many independent variables impact the dependent variable but without manipulating the independent variable. For instance, if the researcher wants to study the effect of terrorism or bomb blasts on the children who have lost their families, then it is difficult to create this situation artificially, so researchers use the quasi-experiments approach. Here, the researcher selects the independent variable instead of manipulating it and compare it with the dependent variable. The researchers will take a group of children who have lost their families (experimental group), and the children who suffered the bomb blast but did not lose their families (control group), and by comparing both these groups, the researcher can analyze the effect of terrorism on the children who lost their families.

2. Observational Method

The observational method is a non-experimental and qualitative research method in which the behavior of the subject under research is observed. An observational method is a great tool for data collection in psychology because the researcher does not require any special types of equipment to collect the research data. We observe several items throughout our day, but psychological researches are different from our daily observations as it involves some important steps such as selection of the area of interest, noting the observations, and analyzing the obtained data. Gathering the data through observation is itself a skill as an observer should be well aware of his actual area of research and he/she should have a clear picture in mind that what qualities or attributes he should observe, and what he should avoid. The researcher should have a good understanding of the correct methods of recording and analyzing the gathered data. The major problem of the observational method is the observer’s biases, there are high chances that the observer may judge the event according to his/her biases rather than interpreting the event in its natural form. We can relate it to a famous saying,

We see things as we are and not as things are”

So, it is the responsibility of the observer to make accurate observations by minimizing his/her biases.

Types of Observations

The observational methods are broadly categorized into the following types,

1. Naturalistic Observation

If the researcher has made the observations in real-life or natural settings such as schools, institutes, homes, open environments, etc., without interfering with the phenomena under observation, then it is known as naturalistic observation. In this type of observation, the researcher does not manipulate or control any situation, and he/she only records the spontaneous behavior of the subject (individual or event under investigation) in their natural environment. Naturalistic observations provide more generalized results because of the natural settings, but it’s difficult to manage the extraneous variables in natural observations and ethical issues of privacy interference and observer bias are some other major problems of naturalistic observations.

2. Controlled Observation

The observations that are conducted in the closed settings, i.e., their various conditions and variable are highly under control, are known as controlled observations. In these observations, variables are manipulated according to the need of the research. For example, if the researcher wants to study the effect of induced workload on the worker’s performance, the research should be conducted in a controlled setting as the researcher can control the independent variable (workload). However, due to the controlled settings approach, these observations are far less to ecological validity than the naturalistic observations, and the behavior of the participants or subjects that are being studied may change because of their awareness of being observed.

3. Participant Observation

The types of observation in which the observer or the researcher itself becomes part of the research are called participant observations. The other participants in the research may or may not be informed about the presence of the observer in the group. However, if the participants are not aware of the observer’s presence, then the results gathered will be more reliable and satisfy ecological validity. In participant observation as the researcher acts as an active member of the observed group, the observer has to be cautious about the fact that other members of the group won’t recognize him/her, and he/she should maintain the proper relationships and a good rapport with the participants under investigation. The strength of the participant observation is that it provides the researcher a holistic approach to understand the process not only from his/her own perspective but also from the participant’s perspective, which reduces the research biases. However, Participant observation is time-consuming, and the findings of this type of observation are usually not generalizable because of the small research groups.

4. Non-Participant Observation

In this type of research, the observer is not present in the research, but he/she uses other means to observe the spontaneous activities or behavior of the individual or group members, this may include installing the camera in the rooms that need to be observed. The main benefit of non-participants’ observation is that the actual behavior of the participants can be observed without making them aware of being under observation. An example of non-participation observation is a school principal who observes the classroom activities of the teacher and students through the CCTV cameras in his/her office.

3. Case Study

In the case study method, the researcher does qualitative research and in-depth analysis of a specific case (subject under investigation). The results obtained from this method are highly reliable; in fact, many famous theories such as the psychoanalytic theory of Sigmund Freud and Jean Piaget’s cognitive development theory are the results of well-structured and proper case studies of the subjects. The case study method allows the researcher to deeply study the psyche of the cases. The researcher does the case studies of the people or events that provide some critical information about the new or less discovered phenomena of the human mind. The number of cases can be one or more, or they are of different or same characteristics, for example, a patient suffering from a mental disorder, a group of people belonging to the same gender, class, or ethnicity, and effect on the people of various natural or man-made disasters such as flood, tsunami, terrorism, and industrialization. Case studies involve the multi-method approach as it uses various other research methods like unstructured interviews, psychological testings, and observations to get detailed information about the subjects. It is the best method to deeply understand and analyze the impact of certain traumatic events on the psychological health of the individual, and it is widely used by clinical psychologists to diagnose various psychological disorders of the patients.

4. Correlational Research

The researcher uses the correlational method if he/she wants to examine the relationship between the two variables. It is to be noted that here researcher does not vary the independent variable as he is only concerned about whether the two variables are linked to each other or not. For example, if you are interested in finding the relation between yoga and the psychological health of the person, then you simply try to find the relationship between these two factors rather than manipulating anything. The degree of the association between the variables is represented by the correlational coefficients ranges from +1.0 to -1.0. The correlation can be of three types, i.e., positive correlation, negative correlation, or zero correlation. If we increase or decrease the value of one variable, the value of another variable also increases or decreases respectively, then it is called a positive correlation, and the value of the correlation coefficient would be near +1.0. If we increase or decrease the value of one variable, the value of another variable decreases or increases respectively, then it is called the negative correlation, and the value of correlational coefficient would be near -1.0, and if the changes in the value of one variable do not affect the other variable, then there does not exist any relationship between the variables, and it is called zero correlation with the correlation value near or equal to zero.

5. Content Analysis

In content analysis research methods, the researcher analyses and quantifies various types of content pieces such as articles, texts, interviews, researches, and other important documents to get useful information about their area of research. Content analyses involve various steps that are data collection, examining the research data, and getting familiar with it, developing ṭhe set of rules for selecting coding units, making coding units (coding unit is the smallest parts of the content that is analyzed) as per the developed rules, and then, finally, analyzing the findings and drawing conclusions. Content analysis is generally of two types, i.e., conceptual analysis, and relational analysis. These are briefly discussed below.

Conceptual Analyses

It involves the selection of the concept (word, phrase, sentence), and then examining the occurrence of the selected concept in the available research data. In conceptual analyses, the researcher selects the sample according to the research question and divides the content into different categories, which makes it easier to focus on the specific data that gives useful information about the research, and then coding and analyzing the results.

Relational Analyses

The initial steps of the relational analyses are the same as the conceptual analyses like selecting the concept, but it’s different from the conceptual analyses because it involves finding the associations or relationships among the concepts. In conceptual analyses, we analyze every concept, but in relational analyses, the individual concepts do not have any importance, instead, the useful information is assessed by finding the associations among the concepts present in the research data.

6. Survey Research Method

Survey research is the most popular mean of data collection in almost every branch of social sciences. It finds its applications in election poll results (election surveys), literacy rate, and population rate analysis. The survey research methods help the researchers understand the actual ground reality of the event by analyzing the social views, attitudes, behavior, and opinions of the people. The researchers use various techniques of survey research methods, which are briefly discussed below.

1. Direct Interviews

An interview process involves direct communication between the interviewer/researcher (who asks the question) and the interviewee/respondent (who answers the questions). Interviews give better in-depth results than any other technique of data collection as the researcher gets first-hand information about the respondent’s mind through communication and observation of his/her behavior. Interviews may be structured or unstructured, when the researcher prepares the sequential list of the questions about when and what questions to be asked in the interview, it is called a structured interview, whereas if the questions to be asked in the interview are not pre-planned, and flexibility is provided to the interviewer to ask questions according to the situation, then it is called the unstructured interview. The responses to the questions in the case of structured interviews are also specified to some extent, such questions are called close-ended questions, while in the case of unstructured interviews, the respondent is free to answer the questions according to his/her desire, and these types of questions are called open-ended questions. For instance, if you ask the respondent whether he/she likes the coffee, then the answer would be either yes or no, i.e., a close-ended question. However, if you ask the respondents about their hobbies, then the respondent will answer it according to his/her will, hence it is an open-ended question. An interview can be of the following types, depending upon the number of interviewers and interviewees involved in the interview. For example,

• One to One Interview: When only the interviewer and one interviewee are present in the interview process.
• Individual to group Interview: When one interviewer interviews a group of people.
• Group to Individual: It is also called group panel interview, in this case, an individual is interviewed by a group of interviewers.
• Group to Group: When a group of interviewers, interviews a group of interviewees.

The most important thing in direct interviews is that the researcher/interviewer should have good interviewing skills, and the ability to build a good rapport with the respondent and making him/her comfortable enough to give accurate answers to the questions asked. The main purpose of conducting an interview is to gather the data about the subject, but the interviewer should be sensitive to the emotions and behavior of the respondent and should not pressurize him/her to give the answers to which he/she is not comfortable enough. The process of the interview is very time-consuming, so it is not much effective as in psychology researches, it would become tedious to take interviews of a large section of society, which is why it is usually preferred for some specific population that may include illiterate or blind people as the interviewer can verbally ask them questions and make sure that whether they understood the questions or not.

2. Telephonic or Digital Surveys

Telephonic surveys involve asking questions about the survey through direct calls or messages. Digital surveys through ‘Google forms’ are also commonly used these days. Telephone and digital surveys are easy to conduct, and they do not consume much time. However, they have many limitations such as the results obtained through them are not much reliable because in this method the researcher does not have proper evidence of certain factors like respondents’ age, gender, and qualifications, etc., and the respondents may have given the manipulative or vague answers.

3. Questionnaires

Questionnaires consist of a well-structured set of questions that are distributed to the people to mark or write the answers. The questions can be open-ended or close-ended, depending upon the type of survey. It is one of the most commonly used survey techniques as it is easy to conduct, less time-consuming, and a cost-effective method to collect research information. It is a better method than the interview for obtaining accurate answers because, in this method, the proper assurance of confidentiality is provided to the respondent, hence the respondent is more likely to mark the accurate answer. Earlier, only paper-based questionnaires were used, but due to the advancement of technology, digital questionnaires, which are sent to people through emails or google forms, are also used these days.

7. Psychological Testing

Psychological testing is also known as psychometrics. Psychological tests are scientifically proven and standardized tests that are constructed by psychologists. These are used to assess the various characteristics of humans such as attitude, aptitude, personality, intelligence quotient, and emotional quotient. There are many psychological tests available these days such as aptitude testing, mental health assessment, educational testing, personality assessment, etc., which are used for different purposes. The multiple-choice questions (MCQs) of the psychological tests are carefully designed, and the factors like gender, age, class, qualification, etc., are considered before conducting these tests. Psychological tests can be conducted offline (pen-paper-based) or online (digital format), depending upon the applicability and availability. The necessary part of the psychological tests is that the participants or the subjects, upon whom the test is conducted, should be properly informed about the testing procedure, and proper instructions about marking or filling the test, time durations of the test, should be verbally provided to them for their better understanding. These tests are constructed by following a systematic approach and three important factors, i.e., validity, reliability, and norms. These are briefly discussed below,

• Validity : The most obvious criterion of constructing the test is that it should be valid. The validity of the test implies that the test should measure what it is designed for. For example, the psychological health assessment test should measure the psychological health of the person rather than the physical health.
• Reliability : The results obtained by the psychological test should be reliable, i.e., there should be almost negligible variations in test scores if the same test is repeated upon the same subjects after some time.
• Norm : For every psychological test, norms are developed, these are the standard values that represent the average performance of the subject or the group of subjects in the tasks that are provided them. Norms enable psychologists to interpret and compare the results obtained by the psychological tests. There are various types of norms for different types of psychological tests such as descriptive norms,  grade norms, age norms, and percentile norms.

Rorschach Psychological Test

Related Posts

Accounting for Hire Purchase

Halo Effect Examples

8 Game Theory Examples in Real Life

3 Allegory of the Cave Examples in Real Life

17 Monopoly Examples in Real Life

Psychology: Definition, Types, Perspectives

Thank you for sharing this very useful knowledge for a psychology student (in this case). Very explanatory, clear to understand. successes.

Well explained 👏 Thanks

Add Comment Cancel Reply

Learning Materials

• Business Studies
• Combined Science
• Computer Science
• Engineering
• English Literature
• Environmental Science
• Human Geography
• Macroeconomics
• Microeconomics
• Experimental Method

A key aim of psychology is to learn and understand more about psychological phenomena. This is usually done through a process called the experimental method . The experimental method in psychology research attempts to investigate the cause-and-effect relationship between variables . The crucial aspect of the experimental method is that it follows a 'scientific routine' to increase the chances of establishing valid and reliable results. As you can expect with all kinds of research, there are many advantages and disadvantages of the experimental method in psychology research. 

Create learning materials about Experimental Method with our free learning app!

• Instand access to millions of learning materials
• Flashcards, notes, mock-exams and more
• Everything you need to ace your exams

Millions of flashcards designed to help you ace your studies

• Cell Biology

What are the three different designs that can be used in the experimental method? 

What is the definition of the experimental method?

What are the three main features of the experimental method?

What does IV stand for, and what is its definition?

What does DV stand for, and what is its definition?

What do extraneous variables affect? 

Can a research be considered valid if many extraneous variables have been found to affect the study? 

What are the different techniques used to improve the validity of research? 

What is an independent group design?

What is a repeated measures design?

What is a matched pairs design?

• Approaches in Psychology
• Basic Psychology
• Biological Bases of Behavior
• Biopsychology
• Careers in Psychology
• Clinical Psychology
• Bartlett War of the Ghosts
• Brain Development
• Bruner and Minturn Study of Perceptual Set
• Case Studies Psychology
• Computation
• Conservation of Number Piaget
• Constructive Processes in Memory
• Correlation
• Data handling
• Depth Cues Psychology
• Designing Research
• Developmental Research
• Dweck's Theory of Mindset
• Ethical considerations in research
• Factors Affecting Perception
• Factors Affecting the Accuracy of Memory
• Formulation of Hypothesis
• Gibson's Theory of Direct Perception
• Gregory's Constructivist Theory of Perception
• Gunderson et al 2013 study
• Hughes Policeman Doll Study
• Issues and Debates in Developmental Psychology
• Language and Perception
• McGarrigle and Donaldson Naughty Teddy
• Memory Processes
• Memory recall
• Nature and Nurture in Development
• Normal Distribution Psychology
• Perception Research
• Perceptual Set
• Piagets Theory in Education
• Planning and Conducting Research
• Population Samples
• Primary and Secondary Data
• Quantitative Data
• Quantitative and Qualitative Data
• Quantitative and Qualitative Methods
• Research Procedures
• Serial Position Effect
• Short-term Retention
• Structures of Memory
• Tables, Charts and Graphs
• The Effects of Learning on Development
• The Gilchrist And Nesberg Study Of Motivation
• Three Mountains Task
• Types of Variable
• Types of bias and how to control
• Visual Cues and Constancies
• Visual illusions
• Willingham's Learning Theory
• Cognition and Development
• Cognitive Psychology
• Data Handling and Analysis
• Developmental Psychology
• Eating Behaviour
• Emotion and Motivation
• Famous Psychologists
• Forensic Psychology
• Health Psychology
• Individual Differences Psychology
• Issues and Debates in Psychology
• Personality in Psychology
• Psychological Treatment
• Relationships
• Research Methods in Psychology
• Schizophrenia
• Scientific Foundations of Psychology
• Scientific Investigation
• Sensation and Perception
• Social Context of Behaviour
• Social Psychology

The experimental method is a research process that involves following scientific guidelines to test hypotheses and establish causal relationships between variables .

• To begin with our learning of the experiment method, we will start with a quick recap covering the elements that make up research.
• We will then move on to discuss the experimental method in psychology research.
• To finish off, we will discuss the advantages and disadvantages of the experimental method in psychology.

Experimental Method of Research

Before we get into the experimental method in psychology research, let's take a quick look at what are the basic components that make up scientific research .

Hypotheses and variables

The hypothesis is an important component of research. The hypothesis is formed at the start of an experiment with the purpose of stating what the researcher expects to find in their study. The hypothesis is important because it is used to identify if the results support or negate psychological theories.

The h ypothesis is a specific, testable statement about the expected outcomes after comparing two (or more) variables.

The hypothesis needs to state the variables being investigated in the research.

The independent variable (IV) is the variable that the researcher manipulates/ changes in their study. This is the variable that the researcher believes these changes in the IV will cause a change in the dependent variable (DV).

The DV is the variable that is being observed and measured. The DV is thought of as the effect that is caused by the changes in the IV.

There are other types of variables, such as extraneous variables, participant variables and situational variables. These are variables that may cause changes in the DV. Ideally, psychology research that follows the scientific method should not have these types of variables. However, it is next to impossible to control for every potential variable that should not affect the DV.

Stages of the experimental method in psychology research

The experimental method has a standardised procedure and has several fixed steps to it that are usually carried out in a lab setting .

• Identify the topic of interest/research and form a hypothesis.
• Identify the IV(s) and DV(s), determine the design and type of experiment, and determine how to measure the IV and DV, e.g. self-report measure, observations, etc.
• Prepare the materials needed in the study and recruit participants through an appropriate sampling method.
• Conduct the experiment in a carefully planned scientific manner, collect the data and statistically analyse the results.
• Write up the lab report, evaluate the study and give suggestions for further research.

Experimental Method Example

A hypothetical study has been described below to show how the experimental method is used in psychology research.

• The researchers researched previously published work on the effects of caffeine on reaction times. The researchers hypothesised that drinking caffeine would affect reaction times based on the previous findings.
• The researchers identified reaction time as the DV and caffeine as the IV; they decided to carry out the study in a lab setting.
• The next stage involved preparing a test that measured reaction times, and participants were randomly assigned to three groups (drink with high levels of caffeine, drink with low levels of caffeine and no caffeine).
• The study was then carried out in a manner to prevent the reliability and validity of the study from being lowered.
• The results of the study were written up in the correct psychology format.

The Features of the Experimental Method

There are three essential requirements of research that follows the experimental method.

We will now discuss each of these and identify how researchers can try and make sure that their research meets these requirements.

Research needs to be considered empirical. Empirical research means that the findings should be reflective of objective facts that the researcher has observed rather than their subjective opinion.

The next requirement, reliability, is important as it makes sure that research findings are consistent across time, in different situations, settings and when applied to other people. When research is found to be reliable, then it is thought that the research findings are representative of the population and can be applied to real-life settings.

Reliability refers to how consistent the results of an experiment are. If the results are similar when the same procedure has been carried out on different occasions, settings or using different participants, then the findings will be considered reliable.

Testing the same study vigorously using the same methodology but on different days, settings, and times or using different samples is used to identify if a study is reliable.

The third requirement of research that follows the experimental method is validity.

Validity is how well a test measures what it intends to.

Validity is important because if the researcher is not in fact measuring what they claim they are measuring, then the results are not accurate and cannot be accurately interpreted or applied. For example, if a test claims it measures personality type but instead measures emotion level, it cannot be a valid test.

The researcher should ensure that their subjective opinion does not influence the research methodology and analysis to ensure research is valid. Researchers can try and combat this through:

Random allocation : Participants are randomly assigned to the experimental or control group; this is used to ensure that individual differences do not cause the results.

Single/Double-blind technique: The researcher is unaware of which experimental condition the participants are in. This prevents the researcher from giving subconscious hints that may influence the participants' behaviour.

Studies that do not use this may measure participants' artificial responses, so the results may not be considered valid.

Types of Experimental Method in Psychology: Experimental Designs

The allocation of participants in experimental/ control conditions is important to ensure that a study is valid. The experimental design is the different ways the participants are split into different conditions/groups of the IV. There are different types of experimental designs .

The independent group's design (IGD)

The IGD is when different participants are assigned to each condition.

When investigating the effect of sleep on reaction times, if using an IGD you would have one group with less sleep (4 hours) and one group with more sleep (11 hours), and the results between the two groups would be compared.

The advantages of this design are that it is less time-consuming than the alternative methods. As different participants are used for each condition there is less chance of participants guessing the hypothesis and altering their behaviour and order effects is not an issue.

However, the disadvantages of this design are that the researcher needs to recruit more participants compared to the other designs. Moreover, there is an increased chance of individual differences influencing the results.

The repeated measures design (RMD)

The RMD is when the same participants are used in all of the conditions.

RMD may be used when investigating if participants are better at memorising information from educational videos or from reading books. The study would involve testing memory after watching an educational video and after reading a book. Each participant would be tested in both conditions.

The advantages of this design are that individual differences will not influence the results of the study as each participant is tested in both conditions and fewer participants may be required to be recruited in comparison to IGD.

In contrast, a disadvantage of this design is that there is a higher risk of order effects influencing the results. This is the idea that the order of conditions tested may influence the study's results.

The matched pairs design (MPD)

The MPD is when participants in each condition are matched on specific variables relevant to the study, e.g. gender, age, IQ, etc.

The advantages of the MPD are that there is no chance of order effects since each condition has a different set of participants and there is less risk of individual differences affecting the results since participants have been matched on such variables.

The disadvantages of this design are that matching participants may be a difficult, costly and time-consuming process.

Advantages and Disadvantages of the Experimental Method in Psychology

Let's move on to discuss the advantages and disadvantages of the experimental method as a whole.

Advantages of the experimental method

• The experimental method gives researchers a high level of control since they choose the IVs and DVs, how to measure them, and the procedure of the study. This means the studies are likely to be high in validity.
• Because of the standardised procedures, experiments can be replicated and their reliability can be tested.

The experimental method allows cause and effect relationships to be determined, which is the goal of psychological research.

The conclusions of these experiments allow useful applications to the real world.

Disadvantages of the experimental method

• Results are subject to human error and subjectivity, e.g. researcher bias, social desirability bias, order effects, etc and so it can be difficult to strictly adhere to the experimental method.
• The procedure of the experimental method can be time-consuming and costly.
• Can include practical problems, e.g. some variables may be hard to manipulate or measure.
• Extraneous variables sometimes can't be controlled, which can lower the validity of a study and its results.
• Participants' behaviour can be influenced by the researcher or the conditions of the experiment.

The Experimental Method - Key Takeaways

• The experimental method is a research process that involves following scientific guidelines to test hypotheses and establish causal relationships between variables.
• There are three important requirements of scientific research that follow the experimental method; these are that research should be empirical, reliable and valid.
• The experimental designs used in psychology research are the independent measures design, repeated measures design and matched pairs design .
• There are advantages and disadvantages of the experimental method in psychology.

Flashcards in Experimental Method 17

The independent measures design, repeated measures design and matched pairs design. 

The experimental method is a research process that involves following scientific guidelines to test hypotheses and establish causal relationships between variables. 

Research should be empirical, reliable and valid. 

Independent Variable (IV) - is the variable that the researcher manipulates/ changes in their study. This is the variable that the researcher believes these changes in the IV will cause a change in the dependent variable (DV). 

Dependent Variable (DV)  - The DV is the variable that is being observed and measured. The DV is thought of as the effect caused by the changes in the independent variable. 

Learn with 17 Experimental Method flashcards in the free Vaia app

We have 14,000 flashcards about Dynamic Landscapes.

Already have an account? Log in

Frequently Asked Questions about Experimental Method

What are the five steps in the experimental method?

The five steps of the experimental method are:

Who used the experimental method?

Some famous researchers who used the experimental method in psychology research are Loftus and Palmer's (1974) experiment on the accuracy of eyewitness testimony, Asch's (1951) Conformity study, and Milgram's (1963) Obedience experiment. 

What is the quasi-experimental method?

The quasi-experimental method is similar to the experimental method in that it tests how changes in the independent variable affect the dependent variable. 

The difference between the two types of the experimental method is that quasi-experimental methods do not randomly assign participants to control and experimental groups, whereas the experimental method does.   

What is the experimental method of psychology?

The experimental method is a research process that involves following scientific guidelines to test hypotheses and establish causal relationships between variables. 

What are the main advantages of the experimental method?

The main advantages of the experimental method are:

• Because of the standardised procedures, experiments can be replicated, and their reliability can be tested.

Test your knowledge with multiple choice flashcards

Can the experimental method be used to identify if there is a cause-and-effect relationship between variables? 

Join the Vaia App and learn efficiently with millions of flashcards and more!

Keep learning, you are doing great.

Discover learning materials with the free Vaia app

Vaia is a globally recognized educational technology company, offering a holistic learning platform designed for students of all ages and educational levels. Our platform provides learning support for a wide range of subjects, including STEM, Social Sciences, and Languages and also helps students to successfully master various tests and exams worldwide, such as GCSE, A Level, SAT, ACT, Abitur, and more. We offer an extensive library of learning materials, including interactive flashcards, comprehensive textbook solutions, and detailed explanations. The cutting-edge technology and tools we provide help students create their own learning materials. StudySmarter’s content is not only expert-verified but also regularly updated to ensure accuracy and relevance.

Vaia Editorial Team

Team Psychology Teachers

• 10 minutes reading time
• Checked by Vaia Editorial Team

Study anywhere. Anytime.Across all devices.

Create a free account to save this explanation..

Save explanations to your personalised space and access them anytime, anywhere!

By signing up, you agree to the Terms and Conditions and the Privacy Policy of Vaia.

Sign up to highlight and take notes. It’s 100% free.

Join over 22 million students in learning with our Vaia App

The first learning app that truly has everything you need to ace your exams in one place

• Flashcards & Quizzes
• AI Study Assistant
• Study Planner
• Smart Note-Taking

Privacy Overview

Get unlimited access with a free vaia account..

• Instant access to millions of learning materials.
• Flashcards, notes, mock-exams, AI tools and more.
• Everything you need to ace your exams.

Purdue Online Writing Lab Purdue OWL® College of Liberal Arts

APA Sample Paper: Experimental Psychology

Welcome to the Purdue OWL

This page is brought to you by the OWL at Purdue University. When printing this page, you must include the entire legal notice.

Copyright ©1995-2018 by The Writing Lab & The OWL at Purdue and Purdue University. All rights reserved. This material may not be published, reproduced, broadcast, rewritten, or redistributed without permission. Use of this site constitutes acceptance of our terms and conditions of fair use.

• Bipolar Disorder
• Therapy Center
• When To See a Therapist
• Types of Therapy
• Best Online Therapy
• Best Couples Therapy
• Managing Stress
• Sleep and Dreaming
• Understanding Emotions
• Self-Improvement
• Healthy Relationships
• Student Resources
• Personality Types
• Sweepstakes
• Guided Meditations
• Verywell Mind Insights
• 2024 Verywell Mind 25
• Mental Health in the Classroom
• Editorial Process
• Meet Our Review Board
• Crisis Support

Classic Psychology Experiments

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

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

Harlow’s Rhesus Monkey Experiments

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

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

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

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

Pavlov’s Classical Conditioning Experiments

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

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

The Asch Conformity Experiments

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

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

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

Skinner's Operant Conditioning Experiments

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

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

Milgram’s Obedience Experiments

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

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

Why This Experiment Is Notable

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

The Stanford Prison Experiment

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

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

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

Van rosmalen L, Van der veer R, Van der horst FCP. The nature of love: Harlow, Bowlby and Bettelheim on affectionless mothers. Hist Psychiatry. 2020. doi:10.1177/0957154X19898997

Gantt WH . Ivan Pavlov . Encyclopaedia Brittanica .

Jeon, HL. The environmental factor within the Solomon Asch Line Test . International Journal of Social Science and Humanity. 2014;4(4):264-268. doi:10.7763/IJSSH.2014.V4.360 

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

B.F. Skinner Foundation. A brief survey of operant behavior .

Gonzalez-franco M, Slater M, Birney ME, Swapp D, Haslam SA, Reicher SD. Participant concerns for the Learner in a Virtual Reality replication of the Milgram obedience study. PLoS ONE. 2018;13(12):e0209704. doi:10.1371/journal.pone.0209704

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

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

Perry G. Deception and illusion in Milgram's accounts of the Obedience Experiments . Theoretical & Applied Ethics . 2013;2(2):79-92.

Specter M. Drool: How Everyone Gets Pavlov Wrong . The New Yorker. 2014; November 24.

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

Experimenter Bias (Definition + Examples)

In the early 1900s, a German high school teacher named Wilhelm Von Osten thought that the intelligence of animals was underrated. He decided to teach his horse, Hans, some basic arithmetics to prove his point. Clever Hans, as the horse came to be known, was learning quickly. Soon he could add, subtract, multiply, and divide and would give correct answers by tapping his hoof. It took scientists over a year to prove that the horse wasn’t doing the calculations himself. It turned out that Clever Hans was picking up subtle cues from his owner’s facial expressions and gestures.

Influencing the outcome of an experiment in this way is called "experimenter bias" or "observer-expectancy bias."

What is Experimenter Bias?

Experimenter bias occurs when a researcher either intentionally or unintentionally affects data, participants, or results in an experiment. 

The phenomenon is also known as observer bias, information bias, research bias, expectancy bias, experimenter effect, observer-expectancy effect, experimenter-expectancy effect, and observer effect. 

One of the leading causes of experimenter bias is the human inability to remain completely objective. Biases like confirmation bias and  hindsight bias  affect our judgment every day! In the case of the experimenter bias, people conducting research may lean toward their original expectations about a hypothesis without the experimenter being aware of making an error or treating participants differently. These expectations can influence how studies are structured, conducted, and interpreted. They may negatively affect the results, making them flawed or irrelevant. In a way, this is often a more specific case of confirmation bias .

Rosenthal and Fode Experiment

One of the best-known examples of experimenter bias is the experiment conducted by psychologists Robert Rosenthal and Kermit Fode in 1963. 

Rosenthal and Kermit asked two groups of psychology students to assess the ability of rats to navigate a maze. While one group was told their rats were “bright”, the other was convinced they were assigned “dull” rats. The rats were randomly chosen, and no significant difference existed between them. 

Interestingly, the students who were told their rats were maze-bright reported faster running times than those who did not expect their rodents to perform well. In other words, the students’ expectations directly influenced the obtained results. 

Rosenthal and Fode’s experiment shows how the outcomes of a study can be modified as a consequence of the interaction between the experimenter and the subject. 

However, experimenter-subject interaction is not the only source of experimenter bias. (It's not the only time bias may appear as one observes another person's actions. We are influenced by the  actor-observer bias  daily, whether or not we work in a psychology lab!)

Types of Experimenter Bias

Experimenter bias can occur in all study phases, from the initial background research and survey design to data analysis and the final presentation of results. 

Design bias

Design bias is one of the most frequent types of experimenter biases. It happens when researchers establish a particular hypothesis and shape their entire methodology to confirm it. Rosenthal showed that 70% of experimenter biases influence outcomes in favor of the researcher‘s hypothesis.

Example of Experimenter Bias (Design Bias)

An experimenter believes separating men and women for long periods eventually makes them restless and hostile. It's a silly hypothesis, but it could be "proven" through design bias. Let's say a psychologist sets this idea as their hypothesis. They measure participants' stress levels before the experiment begins. During the experiment, the participants are separated by gender and isolated from the world. Their diets are off. Routines are shifted. Participants don't have access to their friends or family. Surely, they are going to get restless. The psychologist could argue that these results prove his point. But does it?

Not all examples of design bias are this extreme, but it shows how it can influence outcomes.

Sampling bias

Sampling or selection bias refers to choosing participants so that certain demographics are underrepresented or overrepresented in a study. Studies affected by the sampling bias are not based on a fully representative group.

The omission bias occurs when participants of certain ethnic or age groups are omitted from the sample. In the inclusive bias, on the contrary, samples are selected for convenience, such as all participants fitting a narrow demographic range. 

Example of Experimenter Bias (Sampling Bias)

Philip Zimbardo created the Stanford Prison Experiment to answer the question, "What happens when you put good people in an evil place?" The experiment is now one of the most infamous experiments in social psychology. But there is (at least) one problem with Zimbardo's attempt to answer such a vague question. He does not put all types of "good people" in an evil place. All the participants in the Stanford Prison Experiment were young men. Can 24 young men of the same age and background reflect the mindsets of all "good people?" Not really.

Procedural bias

Procedural bias arises when how the experimenter carries out a study affects the results. If participants are given only a short time to answer questions, their responses will be rushed and not correctly show their opinions or knowledge.

Example of Experimenter Bias (Procedural Bias)

Once again, the Stanford Prison Experiment offers a good example of experimenter bias. This example is merely an accusation. Years after the experiment made headlines, Zimbardo was accused of "coaching" the guards. The coaching allegedly encouraged the guards to act aggressively toward the prisoners. If this is true, then the findings regarding the guards' aggression should not reflect the premise of the experiment but the procedure. What happens when you put good people in an evil place and coach them to be evil?

Measurement bias

Measurement bias is a systematic error during the data collection phase of research. It can take place when the equipment used is faulty or when it is not being used correctly. 

Example of Experimenter Bias (Measurement Bias)

Failing to calibrate scales can drastically change the results of a study! Another example of this is rounding up or down. If an experimenter is not exact with their measurements, they could skew the results. Bias does not have to be nefarious, it can just be neglectful.

Interviewer bias

Interviewers can consciously or subconsciously influence responses by providing additional information and subtle clues. As we have seen in the rat-maze experiment, the subject's response will inevitably lean towards the interviewer’s opinions. 

Example of Experimenter Bias (Interview Bias)

Think about the difference between the following sets of questions:

• "How often do you bathe?" vs. "I'm sure you're very hygienic, right?"
• "On a scale from 1-10, how much pain did you experience?" vs. "Was the pain mild, moderate, or excruciating?"
• "Who influenced you to become kind?" vs. "Did your mother teach you to use manners?"

The differences between these questions are subtle. In some contexts, researchers may not consider them to be biased! If you are creating questions for an interview, be sure to consult a diverse group of researchers. Interview bias can come from our upbringing, media consumption, and other factors we cannot control!

Response bias

Response bias is a tendency to answer questions inaccurately. Participants may want to provide the answers they think are correct, for instance, or those more socially acceptable than they truly believe. Responders are often subject to  the Hawthorne effect , a phenomenon where people make more efforts and perform better in a study because they know they are being observed. 

Example of Experimenter Bias (Response Bias)

The Asch Line Study is a great example of this bias. Of course, researchers created this study to show the impact of response bias. In the study, participants sat among several "actors." The researcher asked the room to identify a certain line. Every actor in the room answered incorrectly. To confirm, many participants went along with the wrong answer. This is response bias, and it happens more often than you think.

Reporting bias

Reporting bias, also called selective reporting, arises when the nature of the results influences the dissemination of research findings. This type of bias is usually out of the researcher’s control. Even though studies with negative results can be just as significant as positive ones, the latter are much more likely to be reported, published, and cited by others. 

Example of Experimenter Bias (Reporting Bias)

Why do we hear about the Stanford Prison Experiment more than other experiments? Reporting bias! The Stanford Prison Experiment is fascinating. The drama surrounding the results makes great headlines. Stanford is a prestigious school. There is even a movie about it! Yes, some biases went into the study. However, psychologists and content creators will continue discussing this experiment for many years.

How Can You Remove Experimenter Bias From Research?

Unfortunately, experimenter bias cannot be wholly stamped out as long as humans are involved in the experiment process. Our upbringing, education, and experience may always color how we gather and analyze data. However, experimenter bias can be controlled by sharing this phenomenon with people involved in conducting experiments first! 

How Can Experimenter Bias Be Controlled? 

One way to control experimenter bias is to intentionally put together a diverse team and encourage open communication about how to conduct experiments. The larger the group, the more perspectives will be shared, and biases will be revealed. Biases should be considered at every step of the process. 

Strategies to Avoid Experimenter Bias

Most modern experiments are designed to reduce the possibility of bias-distorted results. In general, biases can be kept to a minimum if experimenters are properly trained and clear rules and procedures are implemented. 

There are several concrete ways in which researchers can avoid experimenter bias.

Blind analysis

A blind analysis is an optimal way of reducing experimenter bias in many research fields. All the information which may influence the outcome of the experiment is withheld. Researchers are sometimes not informed about the true results until they have completed the analysis. Similarly, when participants are unaware of the hypothesis, they cannot influence the experiment's outcome. 

Double-blind study

Double-blind techniques are commonly used in clinical research. In contrast to an open trial, a double-blind study is done so that neither the clinician nor the patients know the nature of the treatment. They don’t know who is receiving an actual treatment and who is given a placebo, thus eliminating any design or interview biases from the experiment.

Minimizing exposure 

The less exposure respondents have to experimenters, the less likely they will pick up any cues that would impact their answers. One of the common ways to minimize the interaction between participants and experimenters is to pre-record the instructions.

Peer review

Peer review involves assessing work by individuals possessing comparable expertise to the researcher. Their role is to identify potential biases and thus make sure that the study is reliable and worthy of publication.

Understanding and addressing experimenter bias is crucial in psychological research and beyond. It reminds us that human perception and interpretation can significantly shape outcomes, whether it's Clever Hans responding to his owner's cues or students' expectations influencing their rats' performances.

Researchers can strive for more accurate, reliable, and meaningful results by acknowledging and actively working to minimize these biases. This awareness enhances the integrity of scientific research. It deepens our understanding of the complex interplay between observer and subject, ultimately leading to more profound insights into the human mind and behavior.

Related posts:

• 19+ Experimental Design Examples (Methods + Types)
• Backward Design (Lesson Planning + Examples)
• Actor Observer Bias (Definition + Examples)
• Philip Zimbardo (Biography + Experiments)
• Confirmation Bias (Examples + Definition)

Reference this article:

About The Author

Free Personality Test

Free Memory Test

Free IQ Test

PracticalPie.com is a participant in the Amazon Associates Program. As an Amazon Associate we earn from qualifying purchases.

Follow Us On:

Youtube Facebook Instagram X/Twitter

Psychology Resources

Developmental

Personality

Relationships

Psychologists

Serial Killers

Psychology Tests

Personality Quiz

Memory Test

Depression test

Type A/B Personality Test

© PracticalPsychology. All rights reserved

Privacy Policy | Terms of Use