The history of psychology consists of a prescientific and a scientific epoch. The field of psychology as a scientific endeavor is a relatively new discipline, and borders on various other fields, ranging from physiology and the neurosciences to sociology and anthropology.
The end of the 19th century marks the start of psychology as a scientific enterprise. The year 1879 is commonly seen as the start of psychology as an independent field of study, because in that year Wilhelm Wundt founded the first laboratory dedicated exclusively to psychological research.
The 20th century saw a rejection of Freud's theories as being too unscientific, and a reaction against Edward Titchener's abstract approach to the mind. This led to the formulation of behaviorism by John B. Watson, which was popularized by B.F. Skinner. Behaviorism proposed epistemologically limiting psychological study to overt behavior, since that could be quantified and easily measured.
The Ebers papyrus (ca 1550 BC) contains a short description of clinical depression. Though full of incantations and foul applications meant to turn away disease-causing demons and other superstition, it also evidences a long tradition of empirical practice and observation.
In 1879 Wilhelm Wundt founded a laboratory at the University of Leipzig in Germany, specifically to focus on general and basic questions concerning behaviour and mental states. Then in 1890, William James published the book Principles of Psychology which laid many of the foundations for the sorts of questions that psychologists would focus on for years to come. James was the first professor of Psychology at Harvard University.
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