The first generation of psychologists conceived of the discipline as a purely scientific realm. There was initially little thought about applications of psychological knowledge. However, a demand for psychological application soon arose in areas that include advertising, personnel selection, business, and what we now know as human factors. The American Psychological Association’s foundation rested on promoting the science of psychology, so the organization stayed away from endorsing applications. However, on an individual basis people quickly applied psychology widely, as Andrew J. Vinchur documents in The Early Years of Industrial and Organizational Psychology. Psychology today includes robust work in a growing number of applied areas.
Undoubtedly the best-known application of psychological theory today is clinical psychology in mental health areas. Lightner Witmer opened the first psychological clinic in 1906, which treated students struggling in educational settings. He wrote that the term “psychological clinic” might seem unusual, but that was because nobody before him had opened such a clinic. His work was highly influential, as Paul McReynolds illustrates in Lightner Witmer: His Life and Times. This book details the modest beginnings of his clinic, with only a handful of clients in the early years, and the way he grew the clinic in the context of life in the early years of the twentieth century.
As successful as Witmer’s clinic was, the rest of the psychology community did not move in the direction of clinical work for treating people with mental health problems for some time. There were abortive attempts to establish divisions within the American Psychological Association that would relate to counseling, but the movement did not attract many psychologists. However, in the late 1920s the landscape began to shift. Whereas clinical treatment had been the province of psychiatrists with a medical background, psychologists began to establish nonmedical, psychological therapy.
As of the 1920s, psychologists’ role was to assess patients whom psychiatrists would then treat. For the next several decades, psychologists worked to move psychology in the direction of therapy. They faced severe resistance from psychiatrists and other medical professionals in the quest to change the laws regarding who was allowed to provide therapy. In Frontier Struggles: Rollo May and the Little Band of Psychologists Who Saved Humanism, James Schlett illustrates how the provision of mental health services by psychologists was not a foregone conclusion, even though it was clear following World War II that the psychiatric community alone could not meet the demand for mental health services. Psychologists needed to convince legislators that changing the law would lead to positive outcomes; they were successful, but the outcome was far from certain even when legislators were voting on the issue. Schlett also describes how the psychological community moved away from a Freudian model of therapy and in the direction of a humanistic approach of the kind envi-sioned by psychologists like Carl Rogers. Brian Thorne describes Rogers’s significant humanist legacy in the book Carl Rogers.
Once the dominance of Freudian theory waned, psychologists and psychiatrists widened the theoretical scope of treatment to include cognitive and behavioral models. Martin Halliwell’s Therapeutic Revolutions: Medicine, Psychiatry, and American Culture, 1945–1970 documents the changes in the postwar period as psychological thought became embedded in societal norms of the time
The Early Years of Industrial and Organizational Psychology by 
