ABSTRACT
Richard E. Snow, reasoning from his new conception of aptitude, advocated a multidimensional approach to validating the construct of academic achievement. We briefly overview Snow's approach and then summarize evidence from this special issue in 3 themes: (a) the multidimensional structure of science achievement, (b) the incremental predictive validity provided when both cognitive and motivational (affective and conative) constructs are used to model individual differences in achievement, and (c) the co-contributions of ability, motivational orientations, and characteristics of achievement test situations to performance differences. Overall, our studies confirmed or established (a) a multidimensional structure of science achievement scores, (b) the validity of several key motivational constructs for predicting science achievement among high school students, (c) systematic variation in relations be192tween motivational and general-ability constructs and science reasoning dimensions, assessment type, and achievement behavior (performance and anticipated choice), and (d) how alternative assessment methods (constructed response and performance assessment) shed light on the notion of multidimensional validity.
