Exploring the differential effects of aging on controlled and automatic inhibitory tasks

A central goal of cognitive aging research is to understand the fundamental mechanisms responsible for the complex pattern of cognitive changes found in normal aging. This thesis proposes that amending the Inhibitory Deficit Hypothesis (Hasher & Zacks, 1988) to include Nigg’s (2000) distinction between controlled and automatic inhibitory processes provides a parsimonious account of the complex range of age-related declines and preserved levels of functioning found in the literature. This thesis directly explores the effect of aging on controlled and automatic inhibitory tasks. Sixty younger adults (18-35 years old) and sixty older adults (60-79 years old) completed two controlled inhibitory tasks (the Stop Signal task and the Stroop Interference task) and one automatic inhibitory task (the Inhibition of Return task). It was found that older adults performed at a comparable level to younger adults on the automatic inhibitory measure but that older adults demonstrated declining levels of performance on the controlled inhibitory measures. These results provide evidence for a differential effect of aging on controlled and automatic inhibitory tasks. This controlled/automatic distinction helps resolve many of the inconsistencies that are currently present in the cognitive aging literature and provides a sound framework for better understanding cognitive aging.