Aging and Forgetting: Increased Susceptibility to Retroactive Interference?

Abstract

Early pioneering studies into forgetting provided evidence for a Retroactive Interference (RI) account of forgetting (where newly encoded information interferes with encoding of previous learning). That is, memories were said to consolidate over time, with earlier disruption (RI) to this process causing greater forgetting than if the memory trace has had longer to consolidate. More recent investigations into Amnesiacs have provided further evidence for an RI account of forgetting. One such study found that forgetting could be reduced in Elderly patients with Mild Cognitive Impairment (MCI) under conditions of reduced RI compared to Elderly controls, suggesting MCI patients show increased susceptibility to RI. However, little is know about susceptibility to RI associated with normal aging. Previous studies have investigated age-related forgetting over very long (>48 hrs) or very short periods (<3 minutes), varying the time of recall rather than time of interference (with the delay always containing RI). This study explored whether age differences were evident in minimal RI versus interference throughout a 9 minute interval. The present study also investigated whether there was an effect of RI onset time, and if so, whether this differs between a Young group compared to an Elderly group. Three levels of temporal onset were manipulated; with RI occurring early, midway, or late in the delay interval. Results showed that the Elderly group retained significantly fewer words in all RI conditions compared to the Young. Most notably, ageing was associated with greater susceptibility to interference throughout the interval. Results for temporal onset of RI show a significant effect for the Young group with earlier onset of interference associated with greater forgetting; however, the Elderly group showed particular susceptibility to interference presented late in the interval. This was interpreted as evidence for a consolidation account of forgetting as well as a magnified effect of short term interference from late RI and greater retrieval inhibition associated with ageing.