Experimental psychology

Experimental psychology approaches psychology as one of the natural sciences, and therefore assumes that it is susceptible to the experimental method. Many experimental psychologists have gone further, and have assumed that all methods of investigation other than experimentation are suspect. In particular, experimental psychologists have been inclined to discount the case study and interview methods as they have been used in clinical and developmental psychology.

Since it is a methodological rather than a substantive category, experimental psychology embraces a disparate collection of areas of study. It is usually taken to include the study of perception, cognitive psychology, comparative psychology, the experimental analysis of behavior, and some aspects of physiological psychology and developmental psychology.

Ibn al-Haytham (Alhacen) is considered by some to have been a forerunner of experimental psychology, for his experimental approach to the psychology of visual perception and optical illusions in his Book of Optics (1021). An experimental approach was also developed by his contemporary Abū Rayhān al-Bīrūnī, a Persian psychologist who discovered the concept of reaction time. Further progress was not made until the 19th century when Wilhelm Wundt, considered the father of experimental psychology, founded experimental psychology as a discipline and introduced a mathematical and quantitative approach to experimental psychology. Wundt was the first to call himself a "psychologist", and was also the first research/experimental psychologist. He established the first psychology laboratory in Leipzig and he founded the structuralist school of psychology.

Other early experimental psychologists, including Hermann Ebbinghaus and Edward Titchener, included introspection among their experimental methods. However, in the first half of the twentieth century, experimental psychology became closely allied with behaviourism, especially in the United States, and this led to some neglect of mental phenomena. In Europe this was less so, and under the influence of psychologists such as Sir Frederic Bartlett, Kenneth Craik, W. E. Hick and Donald Broadbent, experimental psychologists focused on topics such as thinking, memory and attention. This laid the foundations for the subsequent development of cognitive psychology.

In the latter half of the twentieth century, the phrase "experimental psychology" has shifted in meaning due to the expansion of psychology as a discipline and the growth in the size and number of its sub-disciplines. Experimental psychologists use a range of methods and do not confine themselves to a strictly experimental approach, partly because developments in the philosophy of science have had an impact on the exclusive prestige of experimentation. In contrast, an experimental method is now widely used in fields such as developmental and social psychology, which were not previously part of experimental psychology. The phrase continues in use, however, in the titles of a number of well-established, high prestige learned societies and scientific journals, as well as some university courses of study in psychology.