An old problem revisited : How sensitive is time-based prospective memory to age-related differences?

Prospective memory (PM) tasks that impose strong demands on strategic monitoring decline more in late adulthood relative to tasks dependent on more automatic cue detection processes. This finding has proven robust to numerous manipulations, with one exception: time-based PM. However, conventional time-based tasks may inadvertently present time-related yet still event-based cues. At the same time, prior studies have failed to consider whether time-based age differences vary according to the degree of deliberate strategic processing required to access these cues. In this study, 53 younger and 40 older participants completed three time-based PM conditions in which a response had to be executed when a sand timer completed a cycle. In one condition, this timer could only be accessed by explicit, deliberate monitoring (by pressing a specific key), in a second, it could also be accessed more perfunctorily (simply by altering ones’ visual focus)—and in the third, could not be accessed at all (forcing participants to rely solely on internal temporal estimation processes). Negative age differences emerged in both conditions where participants were able to access the timer, but not in the condition where the timer was hidden. These data provide novel evidence of age-related preservation in at least some aspects of the temporal processing required to support time-based PM. They also suggest that younger and older adults can and do engage in monitoring when given this option, but that only the former group may be able to benefit, even when this monitoring can be conducted relatively perfunctorily.