Episodic memory and age-related deficits in inhibitory effectiveness

Abstract

Background/Study Context: Age-related deficits in inhibitory control are well established in some areas of cognition, but evidence remains inconclusive in episodic memory. Two studies examined the extent to which a loss in inhibitory effectiveness—as measured by the extent of retrieval-induced forgetting (RIF)—is only detectable in (1) the very old, and (2) that a failure to control for noninhibitory mechanisms can lead to the misinterpretation of intact inhibition in episodic memory in the very old.  Methods: In Study 1, the authors employed a modified independent cue test—to provide as clean a measure of inhibitory functioning as possible—and examined whether there were significant differences in inhibitory effectiveness between younger-old (60–64years), old (65–69years), and older-old (70–74years) adults. In Study 2, the authors directly manipulated the contribution of output interference (a noninhibitory mechanism) to RIF in a group of young adults (18–34years), old (61–69years), and older-old (70–85years) adults.  Results: In Study 1, both younger-old (60–64years) and old (65–69years) adults demonstrated RIF on the modified independent cue test but older-old (70–74years) adults did not. In Study 2, all age groups demonstrated RIF in conditions where output interference was promoted. However, when output interference was controlled, only the young (18–34years) and old (61–69years) age groups demonstrated RIF; the older-old (70–85years) age group did not.  Conclusions: The findings suggest that inhibitory functioning remains intact in older adults under the age of 70years. However, a misleading impression can be formed of inhibitory effectiveness in adults over the age of 70 when memory tests do not exclude the use of noninhibitory processes, such as output interference. These two issues may partly explain the previous inconclusive findings regarding inhibitory deficits in normal aging.