The impetus to scientific psychology: a recurrent pattern.

In the nineteenth century, the personal equation, which concerned individual differences in the accuracy of astronomical observations, provided an impetus to the development of experimental psychology. During the first decade of Wundt's laboratory, the measurement of the duration of mental acts received more experimental attention than any other subject. Twentieth century developments in the theoretical physics have stimulated interest in the nature of mental operations and conceptual transformations, a topic which is currently receiving increased attention in psychology. It is suggested that the history of psychology may provide a useful data source for additional work in this area.