paradox? The best answer to this question might be “partly”. Previous research on prospective memory performance in younger adults and older adults revealed heterogeneous results (see Chapter 1.3.2), with the age prospective memory paradox as the most surprising. Therefore, Study 3 further explored the age prospective memory paradox by testing the effect of task setting and motivation on prospective memory performance in younger and older adults. The results of Study 3 clearly demonstrated that the two factors contributed to the pattern of different directions of age effects in laboratory and naturalistic prospective memory tasks.
Yet, task setting and motivation did not exclusively account for the paradoxical findings (see Phillips et al., 2008, for further proposed factors). The age prospective memory paradox can be explored from two directions: (1) investigate possible mechanisms that affect age
impairments in laboratory based tasks; (2) reveal possible factors that might underlie age
benefits in a naturalistic setting. The truth probably lies somewhere in between, as factors in laboratory tasks and mechanism in naturalistic tasks might contribute to the paradoxical findings. Therefore, the present study applied a laboratory based and a naturalistic prospective memory task.
In the laboratory task of Study 3, moving the stop-clock into focal awareness eliminated age differences in the time-check task. This finding nicely dovetails with the multiprocess view (McDaniel & Einstein, 2000), proposing smaller age deficits in focal tasks.
Similar results were obtained in school age children (see Study 2, Chapter 3.2), indicating that the effect of focal task presentation on prospective memory development is already evident in childhood. Furthermore, in line with previous studies conducted on adults (McDaniel et al., 2008), the results of Study 3 underline the importance of task focality contributing to age differences in realizing delayed intentions in adulthood (also for time-based prospective memory). Therefore, future studies need to take the focality of the prospective cue into account. In addition, so far only Rendell and Craik (2000) have examined the effect of task regularity on prospective memory performance. The present results support Rendell and Craik’s (2000) findings, as regular tasks attenuated age differences of prospective
remembering in the laboratory, while age deficits became apparent only in irregular tasks. In previous studies, most laboratory paradigms have used irregular tasks, in which participants could not anticipate the prospective memory task (e.g. virtually every event-based laboratory study in the meta-analysis of Henry et al., 2004). Thus, prospective memory performance of older adults in the laboratory might be underestimated due to the irregular presentation of the prospective task. Following this rationale, the reported age deficits of the age prospective memory paradox in laboratory tasks might be primary to the low performance of older adults in irregular tasks. In contrast, if the elderly had a possibility to anticipate the prospective task, they remembered to perform delayed intentions as often as younger adults, and therefore the age deficits in the laboratory were attenuated. In consequence, if participants can anticipate
the prospective memory task, they may be able to link the necessary information to the ongoing task. Here, the information of the ongoing task may be used to support correct performance of the prospective memory task. In contrast, in an irregular prospective task, no linkage to ongoing activities is possible. Therefore, intrusion of prospective memory task irrelevant information of the ongoing task needs to be avoided. Executive functions are assumed to be the underlying mechanism of this ability, particularly inhibition and working memory. Hence, declining executive functions might be related to lower performance of older adults in irregular prospective memory tasks. Inhibition is the ability to ignore distractions and stay focused. An age-related decline of inhibitory control is found across adulthood (e.g.
Hasher & Zacks, 1988; see Jurado & Rosselli, 2007, for an overview). As a result older adults are assumed to be preoccupied with task-irrelevant information. In addition, reduced working memory might be especially critical in irregular tasks, as information about the prospective task needs to be ready to retrieve during the entire time of performing the ongoing activity. In contrast, regular tasks enable participants to minimize working memory requirements by providing fixed periods to retrieve the delayed action. Studies on working memory
development in early and later adulthood have indicated a climax in early adulthood and have shown a declining trajectory across the lifespan (see Park & Payer, 2006, for an overview).
Thus, age differences in prospective memory performance might be affected by diminishing inhibitory control and working memory capacity.
The second aspect of the age paradox is the finding of age benefits in naturalistic tasks (see Henry et al., 2004, for an overview). Various factors are assumed to affect prospective memory performance of young and old adults in naturalistic tasks (see Phillips et al., 2008 for an overview). Amongst them, Maylor (1993a) proposed that differences in motivation may cause age benefits in prospective remembering. In detail, low motivation in younger adults might increase age differences. Therefore, in Study 3 motivation to perform the naturalistic prospective memory task was varied by applying monetary incentives. The results showed
that while performance of older adults did not increase in the incentive condition, younger adults performed significant better if incentives were provided. This finding supports the assumption of motivation influencing prospective remembering. Hence, age benefits in naturalistic tasks might be, at least partly, due to the low motivation of young adults to perform the tasks. Thus, the view of age benefits in naturalistic prospective memory tasks might need to be reframed: the performance of older adults in a naturalistic environment is not necessarily enhanced, based on various mechanism (e.g. use of reminder, Kvavilashvili &
Ellis, 2004), instead young adults performance may be reduced as they do not utilise their prospective memory abilities, due to low motivation to perform the tasks.
In sum, the results of Study 3 indicate that several factors underlie the paradoxical age-related findings of laboratory-based and naturalistic prospective memory tasks; two of these are task setting in the laboratory and motivation in naturalistic tasks.
Future studies should further explore the relation of task regularity and task focality on prospective memory performance in adulthood. Especially the effects of task motivation should be taken into account when further investigating the age prospective memory paradox.
In addition, the role of possible cognitive resources underlying the age-related decline in prospective memory performance, like inhibitory control and working memory, should also be directly examined in future research.
5.2 Conceptual implications of the present findings: Prospective memory across the