ABSTRACT
In the domain of human learning and memory, the study of individual and developmental differences offers a variety of attractions. Foremost among these, if one especially values the role of explorer, is the sheer magnitude of the phenomena to be explained-the vast extent of the unknown. To be sure, what a person learns and the circumstances of his learning have substantial effects on his apparent proficiency, but the amount of variation produced by such factors typically falls far short of the amount associated wi th differences among learners.
