The role of memory traces quality in directed forgetting: A comparison of young and older participants using the list procedure

Discrepant results are observed about the Directed Forgetting (DF) effect in healthy aging when the list method is used. The present study aimed at investigating if preserved DF effect is due to a decline in the ability to self-initiate efficient encoding strategies, or efficient retrieval-inhibition processes. We predicted that increasing the strength of memory traces by favoring deep information encoding would be associated with attenuation of DF effects in older participants by comparison to younger ones, due to the increased inhibitory difficulty. Forty young and 40 older participants were submitted to a list-based directed forgetting paradigm, with two encoding conditions: standard and enriched (longer presentation time and proposal of mnemotechnic strategies). We observed the expected effects of age, encoding condition and item type (p < 0.05). When directly comparing performance of older participants in the enriched encoding condition to that of younger participants in the standard one, the results were very similar between groups, which is in contradiction with our initial hypothesis. Discussion. These results do not argue in favor of a reduction of inhibitory mechanisms underlying DF with age but are better explained by between-groups episodic memory differences.