Episodic memory and age-related deficits in inhibitory effectiveness

While an age-related deficit in inhibitory control is well-established in some areas of cognition, the evidence for such a deficit in episodic memory remains inconclusive. Two novel retrieval practice studies were conducted to clarify this issue via 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 non-inhibitory mechanisms can lead to the misinterpretation of intact inhibition in episodic memory in the very old. In Study 1, we chose not to cue practised stronger items at final test and employed independent cues throughout in order to provide as clean a measure of inhibitory functioning as possible. Three groups of older adults were tested: younger-old (60-64 years), old (65-69 years), and older-old (70-74 years). RIF effects emerged in all age groups except in the older-old. In Study 2, we directly manipulated the contribution of output interference (a non-inhibitory mechanism) in a group of young adults (18-34 years), and two older age groups (61-69 years and 70-85 years). Forgetting effects consistent with intact inhibition emerged in young adults and in older adults under the age of 70 years but not in adults over 70 years. In conditions where output interference was promoted, RIF effects also emerged in adults over 70 years thereby giving the misleading impression that inhibitory functioning remains intact. Implications for memory retrieval, measurement, and the modelling of cognitive inhibition in older age are considered.