A History of Modern Psychology

Scientific psychology was sustained by the idea that the natural sciences could be expanded to encompass the study of human beings and society. As I emphasized in Chapter 2, the natural sciences, and physics in particular, represented an ideal for many psychologists. When Watson and other behaviorists claimed that the field could be based on objective observations of behavior and not on mental processes, it led some to expect a closer approximation to the ideal the natural sciences represented. In the 1920s and 1930s, many US psychologists thought behaviorism had taken psychology an important step towards its establishment as a natural science. But it was also obvious to many that although the behaviorist approach was adopted as the point of departure, the procedures used in this field were vastly inferior to those employed in physics.

One compelling difference was, of course, the extensive use of measurements and mathematics in physics. This difference had already been noted in the time of Fechner and Galton. In the 1920s and 1930s, there was an extensive effort to develop better methods to measure intelligence. As we shall see in the next two chapters, advances were made in the use of statistical and mathematical models in social and personality psychology. But progress in measurement and mathematical treatment had been slow.

There were other ways in which the scientific activity of psychology and physics differed. Physicists had developed theoretical systems from which to deduce consequences they could compare to observations. Researchers in psychology, however, most often restricted themselves to describing the phenomena they studied and making inductive inferences from observations. In their influential accounts of the nature of science, Mill and Mach had emphasized inductive procedures. In the 1930s and 1940s, behaviorists as well as psychologists with a cognitive orientation began to concentrate more on issues related to the construction of theory.

In his attempt to build a comprehensive theory of personality, Freud had postulated the existence of inner states and forces in the organism. The behaviorists turned against all accounts of psychological events that were based on assumptions about mental states.