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.
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?
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,
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