What is Experimental Psychology?

August 12, 2019
Experimental psychology focuses on scientific research and experiments in order to study the relationship between human behavior and the mind in-depth.

To arrive at a precise and safe conclusion, researchers often employ different scientific methods. This is what experimental psychology mainly focuses on. Experimental psychology explores basic concepts such as memory and motivation in areas such as child, social, and educational psychology.

Almost all experimental psychology work is carried out in controlled environments like research laboratories. Experimental psychologists manipulate research variables to explore the relationship between cognition and behavior.

While the other branches of psychology strive to understand human behavior and thought processes, experimental psychology focuses on conducting controlled experiments with designated variables, test subjects, and statistical results.

The origin of experimental psychology

For many, Charles Darwin and his work On the Origin of Species initiated the field of experimental psychology. On one hand, there’s no doubt that Darwin’s revolutionary theory sparked interest in the relationship between biology and psychology. In the early 1900s, psychologists began using natural sciences to analyze and explain the human mind.

However, functionalist theories replaced people’s inaccurate thought of the human mind being a machine. For example, William James, the father of American psychology, was strongly influenced by evolutionary biology. He promoted the idea that the mind is naturally adaptive, sensitive, and intelligent.

In the end, it was behaviorism and other branches of modern psychology that contributed to what we know today as experimental psychology.

A drawing of a brain.

What do experimental psychologists do?

Experimental psychologists seek to study behaviors and the different processes and functions that support them. They test subjects to understand and learn about different topics like perception, memory, sensation, learning, motivation, and emotions.

For these psychological studies to be reliable, four fundamental principles must be present:

  • Determinism: Experimental psychologists, like most scientists, accept the concept of determinism. It refers to the assumption that the state of an object or event is determined by its previous states. In other words, cause and effect usually originate behavioral or mental phenomena. If a phenomenon is general and widely confirmed, one could say it’s a ‘law’. Psychological theories serve to organize and integrate laws.
  • Empiricism: Knowledge mainly comes from experiences related to the senses. Therefore, the only things we can study are those that are observable. The concept of empiricism requires a contrast between hypotheses and theories with observations of the natural world and not with previous reasoning, intuition, or revelation.
  • Parsimony: It’s the search for simplicity. According to this principle, research must be carried out on the simplest of theories. If we face two different, contrasting theories, we’d prefer the most parsimonious or basic one.
  • Probability: According to this principle, hypotheses and theories should be testable over time. Scientists consider a theory meaningless if they can’t prove it in any conceivable way. Probability implies ‘falsifiability’, which is the idea that a set of observations could prove a theory wrong.

We can also add operationalism to these definitions. It implies that a concept is defined in terms of concrete and observable procedures. Experimental psychologists try to define currently unobservable phenomena by connecting them to observations and reasoning.

Reliability and validity

Reliability measures the consistency, verifiability, or repeatability of a study. If the research delivers the same results when repeated (either in a different set of participants or over a different period of time), then one can consider it reliable.

On the other hand, validity measures the relative precision or accuracy of the conclusions drawn from a study. It refers to the relative accuracy of psychological studies. To determine the validity of a quantitative measure, one must compare it with a criterion.

Here are the several types of validity:

  • Internal validity: The study provides strong evidence of causality between two factors. A study that has a high internal validity reaches the conclusion that, in fact, the manipulation of the independent variable is responsible for the changes in the dependent variable.
  • External validity: The study would deliver the same results even when applied to a different population.
  • Construct validity: The researcher finds that the independent and dependent variables are precise representations of the abstract concepts that are being studied.
  • Conceptual validity: In which the hypothesis that was being tested supports the broader theory that the researcher is also studying.
Researchers making use of experimental psychology methods.

Final comments

Although many consider experimental psychology a branch of psychology, all areas of psychology use experimental methods.

For example, developmental psychologists use experimental methods to study how people grow during childhood and throughout life.

Social psychologists, on the other hand, use experimental techniques to study how groups influence people. On the other hand, health psychologists also use experimentation to better understand the factors that contribute to well-being and diseases.

  • Boring, Edwin G. (1950). A History of Experimental Psychology Prentice-Hall.
  • García Vega, L. (1985). Lecciones de historia de la psicología. Madrid: Editorial de la Universidad Complutense.
  • Leahey, T. (1998). Historia de la psicología. Madrid: Prenti Hall.
  • Solso, Robert L. & MacLin, M. Kimberly (2001). Experimental Psychology: A Case Approach. Boston: Allyn & Bacon.