This chapter is concerned with two major issues:

and

Answering these questions from presently available knowledge requires prior discussion of several terminological and methodological issues. Such terms as “speed,” “power,” and “level” have had varying interpretations and operationalizations that must be carefully observed and distinguished. After reviewing the ways in which these terms have been used and setting forth the definitions that are to be employed in subsequent discussion, I review a number of models that have been proposed for interpreting the rates at which cognitive tasks are performed.

Next, studies of relations among rates of task performance, levels of task mastery, and task difficulty are reviewed. In the course of this review, attention is directed to the relatively few factor-analytic studies that have been specifically addressed to identifying speed-of-performance abilities as distinct from level-of-mastery factors.