Measurements of various parameters derived from different reaction time (RT) paradigms are found to be correlated with psychometric measurements of general mental ability. Such RT-derived measurements, when combined in a multiple regression equation, predict some 50 percent or more of the variance in intelligence. This relationship of intelligence to RT parameters indicates that our standard intelligence tests tap fundamental processes involved in individual differences in intellectual ability and not merely differences in specific knowledge, acquired skills, or cultural background. Three distinct RT experiments are described. The Hick procedure measures the increase in RT as a function of the amount of information conveyed by the reaction. The Sternberg procedure presents a small set of symbols followed immediately by a single probe to which the subject responds yes or no. The Posner procedure requires the subject to respond to pairs of stimuli, judged either physically or semantically, as the same or different. (Author/CTM)