The goal of this research project was to discover those personality characteristics of college students which predispose them towards learning more effectively from one, rather than some other, particular instructional format. Over 800 students in each of two college courses were taught by one of four different methods, and three broad classes of criterion information were assessed: (a) knowledge of course content, (b) amount of extra-curricular reading, and (c) degree of student satisfaction. Each student completed an extensive battery of personality measures, which yielded over 350 test scores. The ratio of significant interaction effects to the number expected by chance was only 4 to 3. Consequently, new interaction scales were developed empirically in each course, and these were then cross-validated in the other course. In general, these new scales did not produce statistically significant interaction effects upon cross-validation, and scales constructed from items which produced significant interactions in both courses showed low internal consistency and low convergent validity. Factors which could have attenuated the strength of trait-by-treatment interaction effects are discussed.Over the years, in a continued effort to improve the practice of higher education, a number of investigators have attempted to assess the differential effects of various teaching procedures upon student achievement in college courses. The instructional methods which have been compared in studies of this gort can be divided into at least two major types: (a) variations in * The report is a summary of the findings presented in Goldberg (1969), a monograph which is available to readers wishing additional details of the investigation. Help with the design and implementation of the project was generously provided by William A. Bricker, Leslie A. Davison, and Vello Sermat. The author also wishes to acknowledge, with great thanks, the research contributions of