J. Bruce Overmier
University of Minnesota

William E. Montague
Navy Personnel Research & Development Center

James J. Jenkins
University of South Florida

A little over 30 years ago Lee Cronbach published a seminal article in which he
challenged psychologists to integrate the two disjoint disciplines of differential
and experimental psychology. Cronbach specifically called for the study of the
interactions between individual differences variables (aptitudes) and experimen-
tal manipulations (or treatments). Such interactions have become generically
known to differential, educational, industrial/organizational, personality, and
experimental psychologists as aptitude-treatment interactions. Following the ap-
pearance of Cronbach's article, several researchers turned their attention to this
area. Some of the most significant discussions emerging from this area have
pertained to the study of individual differences in learning.

The task at hand has not been an easy one, though. An early conference in
1965 on these issues held at the University of Pittsburgh ( R. M. Gagné, Editor,
Learning and Individual Differences. Columbus, Ohio: Charles E. Merrill)
paved the way for later advances in research in this area, and anticipated many
subsequent developments in the information processing approach to human abili-
ties. Other conferences have looked specifically at relevant methodological is-
sues, such as the one at the University of Wisconsin in 1962 ( C. W. Harris,
Editor, Problems in Measuring Change, Madison, Wisconsin: University of
Wisconsin).

Although there has been substantial growth during the past decade in research
concerned with ability, motivation, and methodological approaches to learning
and individual differences, much of this research has developed along parallel
tracks, with too limited interaction between researchers who investigate related
topics. However, guided by contemporary theories of cognition from the
mid-1970s, many productive research programs have been initiated in psychol-

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