Aging, inhibition, working memory, and speed.

An implication of the hypothesis that failures of inhibition contribution to adult age differences in working memory (Hasher & Zacks, 1988) is that statistical control of measures of inhibition should reduce the age-related effects on working memory. This implication was tested in a study in which interference measures from three variants of a Stroop task served as the measures of inhibition. Although the age-related variance in measures of working memory was substantially reduced after control of the interference measures, the degree of attenuation was at least as large when speed measures from other tasks were controlled. Furthermore, additional analysis revealed that speed measures from tasks requiring oral, written, and keypress responses shared large proportions of their age-related variance. It was suggested that age-related influences on specific processes, such as inhibition, cannot be accurately assessed unless the contributions of more general age-related influences are taken into consideration.