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 (among others) sensation, perception, memory, cognition, learning, motivation, emotion; developmental processes, social psychology, and the neural substrates of all of these.

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.^{[citation needed]} He wrote a pamphlet summarizing his research on rabbits. His research concluded that sensory nerves enter at the posterior (dorsal) roots of the spinal cord, and motor nerves emerge from the anterior (ventral) roots of the spinal cord.^{[citation needed]} 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 ${\displaystyle I\!}$ is the original intensity of stimulation, ${\displaystyle \Delta I\!}$ is the addition to it required for the difference to be perceived (the jnd), and k is a constant. Thus, for k to remain constant, ${\displaystyle \Delta I\!}$ must rise as I increases. Weber's law is considered to be the first quantitative law in the history of psychology.

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 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.

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 (Einstellung) 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.