A branch of psychology concerned with developing a scientifically defensible conception of human nature—in modern parlance, a general theory of behavior. Personality theory is an outgrowth of nineteenth-century French and German psychiatry. Nineteenth-century psychiatry was a practical rather than an academic discipline, concerned with the origins and treatment of psychopathology. It dealt with abnormal rather than normal thought processes and focused on the unconscious rather than the conscious mind. Perhaps most distinctively, it considered a single person as the unit of study, in contrast to academic psychology's focus on a single perception or behavioral response. These themes continue today. Thus, with only a few exceptions, the prominent personality theorists have been psychiatrists or clinical psychologists, and personality psychology has developed largely outside the mainstream of academic psychology. The major exceptions are those personality theorists who have a behaviorist orientation, who stress the role of learning in personality development: John Dollard, Neal Miller, Albert Bandura, and Walter Mischel.