A brief historical overview of Intraindividual variability research across the life Span

Although we believe that these two classes of sciences can inform each other in constructive ways and are not necessarily mutually exclusive, they were treated as such for a long time in the history of psychology, resulting in two distinct approaches to the study of human behavior. Indeed, in 1957, Cronbach elaborated on “the two disciplines of scientific psychology” in his address as president of the American Psychological Association, relating experimental psychology to the nomothetic tradition and correlational psychology (more or less) to the idiographic tradition. Interestingly, Cronbach also noted in his address that “psychology continues to this day to be limited by the dedication of its investigators to one or the other method of inquiry rather than to scientific psychology as a whole” (p. 671).