Experimental psychology
Experimental psychology is the work done by those who apply experimental methods to psychological study and the underlying processes. Experimental psychologists employ human participants and animal subjects to study a great many topics, including sensation, perception, memory, cognition, learning, motivation, emotion; developmental processes, social psychology, and the neural substrates of all of these.
History
Early experimental psychology
Wilhelm Wundt
Experimental psychology emerged as a modern academic discipline in the 19th century when Wilhelm Wundt introduced a mathematical and experimental approach to the field. Wundt founded the first psychology laboratory in Leipzig, Germany. Other experimental psychologists, including Hermann Ebbinghaus and Edward Titchener, included introspection in their experimental methods.Charles Bell
was a British physiologist whose main contribution to the medical and scientific community was his research on the nervous system. He wrote a pamphlet summarizing his research on rabbits. His research concluded that sensory nerves enter at the posterior roots of the spinal cord, and motor nerves emerge from the anterior roots of the spinal cord. Eleven years later, a French physiologist, Francois Magendie, published the same findings without being aware of Bell's research. As a result of Bell not publishing his research, this discovery was called the Bell–Magendie law to honor both individuals. Bell's discovery disproved the belief that nerves transmitted either vibrations or spirits.Ernst Heinrich Weber
, a German physician, is credited as one of experimental psychology's founders. Weber's main interests were the sense of touch and kinesthesis. His most memorable contribution to the field of experimental psychology is the suggestion that judgments of sensory differences are relative and not absolute. This relativity is expressed in "Weber's Law," which suggests that the just-noticeable difference or jnd is a constant proportion of the ongoing stimulus level. Weber's Law is stated as an equation:where is the original intensity of stimulation, is the addition to it required for the difference to be perceived, and k is a constant. Thus, for k to remain constant, must rise as I increases. Weber's law is considered to be the first quantitative law in the history of psychology.
Gustav Fechner
published in 1860 what is considered to be the first work of experimental psychology, "Elemente der Psychophysik." Some historians date the beginning of experimental psychology to the publication of "Elemente." Ernst Heinrich Weber was not a psychologist, but it was Fechner who realized the importance of Weber's research to psychology. Weber's law and Fechner's law was published in Fechner's work, "Elemente der Psychophysik," and Fechner, a student of Weber named his first law in honor of his mentor. Fechner was profoundly interested in establishing a scientific study of the mind-body relationship, which became known as psychophysics. Much of Fechner's research focused on the measurement of psychophysical thresholds and just-noticeable differences. He invented the psychophysical method of limits, the method of constant stimuli, and the method of adjustment, which are still in use.Oswald Külpe
Oswald Külpe is the main founder of the Würzburg School in Germany. He was a pupil of Wilhelm Wundt for about twelve years. Unlike Wundt, Külpe believed experiments were possible to test higher mental processes. In 1883 he wrote Grundriss der Psychologie, which had strictly scientific facts and no mention of thought. The lack of thought in his book is odd because the Würzburg School put a lot of emphasis on mental set and imageless thought.Würzburg School
The work of the Würzburg School was a milestone in the development of experimental psychology. The School was founded by a group of psychologists led by Oswald Külpe, and it provided an alternative to the structuralism of Edward Titchener and Wilhelm Wundt. Those in the School focused mainly on mental operations such as mental set and imageless thought. Mental set affects perception and problem solving without the awareness of the individual; it can be triggered by instructions or by experience. Similarly, according to Külpe, imageless thought consists of pure mental acts that do not involve mental images. William Bryan, an American student, working in Külpe's laboratory, provided an example of mental set. Bryan presented subjects with cards that had nonsense syllables written on them in various colors. The subjects were told to attend to the syllables, and in consequence, they did not remember the colors of the nonsense syllables. Such results made people question the validity of introspection as a research tool, leading to a decline in voluntarism and structuralism. The work of the Würzburg School later influenced many Gestalt psychologists, including Max Wertheimer.George Trumbull Ladd
introduced experimental psychology into the United States and founded Yale University's psychological laboratory during his time there. In 1887, Ladd published Elements of Physiological Psychology, the first American textbook that extensively discussed experimental psychology. Between Ladd's founding of the Yale Laboratory and his textbook, the center of experimental psychology in the US shifted to Johns Hopkins University, where George Hall and Charles Sanders Peirce were extending and qualifying Wundt's work.Charles Sanders Peirce
With his student Joseph Jastrow, Charles S. Peirce randomly assigned volunteers to a blinded, repeated-measures design to evaluate their ability to discriminate weights. Peirce's experiment inspired other researchers in psychology and education, which developed a research tradition of randomized experiments in laboratories and specialized textbooks in the 1800s. The Peirce-Jastrow experiments were conducted as part of Peirce's pragmatic program to understand human perception; other studies considered perception of light, etc. While Peirce was making advances in experimental psychology and psychophysics, he was also developing a theory of statistical inference, which was published in "Illustrations of the Logic of Science" and "A Theory of Probable Inference" ; both publications that emphasized the importance of randomization-based inference in statistics. To Peirce and to experimental psychology belongs the honor of having invented randomized experiments decades before the innovations of Jerzy Neyman and Ronald Fisher in agriculture.Peirce's pragmaticist philosophy also included an extensive theory of mental representations and cognition, which he studied under the name of semiotics. Peirce's student Joseph Jastrow continued to conduct randomized experiments throughout his distinguished career in experimental psychology, much of which would later be recognized as cognitive psychology. There has been a resurgence of interest in Peirce's work in cognitive psychology. Another student of Peirce, John Dewey, conducted experiments on human cognition, particularly in schools, as part of his "experimental logic" and "public philosophy."
20th century
In the middle of the 20th century, behaviorism became a dominant paradigm within psychology, especially in the United States. This led to some neglect of mental phenomena within experimental psychology. In Europe, this was less the case, as European psychology was influenced by psychologists such as Sir Frederic Bartlett, Kenneth Craik, W.E. Hick, and Donald Broadbent, who 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 20th century, the phrase "experimental psychology" had shifted in meaning due to the expansion of psychology as a discipline and the growth in 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 affected the exclusive prestige of experimentation. In contrast, experimental methods are now widely used in fields such as developmental and social psychology, which were not previously part of experimental psychology. The phrase continues in use 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.