Time-based and event-based prospective memory across adulthood: underlying mechanisms and differential costs on the ongoing task.

The authors investigated the phenomenon that performance in an ongoing task declines when individuals must carry out a prospective memory (PM) task. This effect is referred to as the PM interference effect. The authors examined whether the PM interference effect differs between event-based and time-based PM tasks and whether it is increased among the elderly. The authors also investigated adult age differences in PM performance and the potential underlying mechanisms of the age deficits in PM. They found that the PM interference effect was greater in event-based than in time-based tasks. However, aging was not associated with an increase in PM interference effects. Age differences in PM performance were more exaggerated in time-based than event-based PM, but they were not mediated by age differences in traditional cognitive ability measures. In time-based PM, age showed a unique adverse effect even after controlling for the ability to externally monitor the time, leading to the possibility that aging disrupts time-based PM because of deficits in internally processing the time.