Discussion of research questions

7.1.1 Does personal task importance, use of reminders, and everyday stress affect adult age differences in everyday PM? (Study 1)

The first research question evaluated in the present work can be answered with “yes and no”. First of all, results from Study 1 (see Chapter 4) suggest that the age benefit found in experimenter-given naturalistic PM tasks can be generalized to real life PM with intentions

naturally occurring in everyday life. As a variety of daily intentions were examined, present results extend the literature, which so far has focused on medication adherence as naturally occurring intentions and thus followed the suggestions of Phillips et al. (2008) who

underlined the need to study everyday PM in a larger variety of intentions.

A further aim of Study 1 was to provide a first exploration of several factors that may be associated with age differences in everyday PM. First, concerning the role of personal task importance, there was an interaction between task importance and age group indicating that older adults only outperformed younger adults in PM tasks with medium and lower levels of importance, whereas in PM tasks with the highest level of importance, both age groups

showed perfect PM performance and thus comparable PM accuracy. This result of eliminating age benefits in high importance tasks by increasing accuracy especially in younger adults is largely in line with the study by Aberle et al. (2010) and confirms the major role motivational factors may have in age-related PM also for naturally occurring PM tasks. However, in

contrast to Aberle et al. (2010), personal importance also supported older adults’ PM (in terms of a performance increase from the lowest to the medium level of importance) which indicates that task importance in the context of everyday PM may be an important factor not only in younger adults (see Section 7.2.4.3, for an illustration of possible underlying mechanisms).

Second, present findings showed that use of reminders was beneficial for PM performance (see Section 7.2.4.3, for an illustration of possible underlying mechanisms).

However, there were no age differences in the use of reminders and the PM age benefit was not attributable to greater use of reminders. This suggests that in real life intentions, younger and older adults make use of reminders but rather in the same way: Both age groups

substantially increased the use of reminders if an intention was very important and the use of reminders supported prospective remembering in both age groups. In sum, present results stand against the popular view of reminder use being responsible for age benefits in PM in everyday life. Instead, they corroborate previous studies on experimenter-given PM tasks

showing that the use of reminders cannot explain age-related PM performance in the naturalistic setting (e.g., Rendell & Craik, 2000; Rendell & Thompson, 1999).

Third, everyday stress was identified as a detrimental factor on PM performance in general, which is in line with previous results (e.g., Schnitzspahn et al., 2011; see Section 7.2.4.3, for an illustration of possible underlying mechanisms). However, there were no age differences in everyday stress and the PM age benefit was not due to lower stress levels in everyday life. This suggests that - even when comparing students with retired older adults as in Study 1 - it is unlikely that age-related naturalistic PM performance is caused by age differences in everyday stress. Similar in this context, concerning the demands due to the amount of planned activities, present findings showed that overall younger adults had more intentions for the following day than older adults. One may argue that it might not be

surprising that younger adults have lower PM performance when they have more intentions to remember. However, present data showed that the number of intentions did not predict PM performance in general and was not related to the age effect in particular. Thus, the lower PM performance in younger compared to older adults could not be simply explained by the fact that younger adults had more intentions. In sum, daily demands associated with everyday stress or due to the amount of intentions did not contribute to age differences in everyday PM.

Fourth, interestingly, older adults reported more often that they had consciously decided to change and reschedule intentions. Moreover, reprioritizing was related to better PM performance and when taken into account in subsequent analyses, it eliminated the PM age benefit (see Section 7.2.4.3, for an illustration of possible underlying mechanisms). On first glance one may argue that it is somewhat trivial that the age effect in the fulfillment of intentions is eliminated when one of the two major categories of non-completion is taken into account. However, note that PM performance was only calculated after excluding those intentions that were reprioritized (similarly to excluding those intentions in traditional

laboratory PM research for which the participant had no retrospective memory anymore at the

end of the procedure). Thus, PM errors reflected true and individually validated PM failures.

Furthermore, as discussed in Study 1, it is unlikely that the better PM performance of older adults can be simply explained by reprioritization as an “excuse” for actually forgotten

intentions: Participants’ reports were only post-hoc categorized to avoid priming this response bias and participants had to give plausible reasons for reprioritizing in order to categorize a non-completed intention in this category. In sum, this first exploration of underlying

mechanisms in age differences in everyday PM suggests that ability of flexibly rescheduling intentions may be a key issue.

Taken together, the major finding of Study 1 suggests that age benefits in naturalistic PM performance transfer to real life PM tasks and hence beyond artificial, experimenter-given tasks. Considering that there is only little known about real life PM so far, this is a novel finding with the conceptual implication that the pattern of PM age benefits in the naturalistic setting can be expected regardless whether PM tasks are experimenter-given or whether fulfillment is passively observed for daily intentions. This progress in PM research could be entitled “from lab to life”. Furthermore, the investigated underlying mechanisms played a different role: Personal task importance and rescheduling of intentions seem to be important factors in the light of explaining the age benefit in everyday PM. However, the use of

reminders and everyday stress as often suggested underlying mechanisms for naturalistic PM age differences did not receive empirical support from the present data. These findings will be discussed with respect to a broader conceptual perspective in Section 7.2.1 for personal task importance and use of reminders, 7.2.2 for reprioritization of intentions, and 7.2.3 for everyday stress. In general, an interesting question is why we can observe that older adults perform better in naturalistic PM tasks while we find robust PM age deficits in the laboratory.

In other words, how can we explain the paradoxical reversal of PM age effects in the field?

This question will be discussed in detail in Sections 7.2.4.3 and 7.2.4.4.

7.1.2 Does task order specificity influence adult age differences in event-based laboratory PM? (Study 2)

The second research question can clearly be answered with “yes”. Meta-analytic results from Study 2 (see Chapter 5) revealed that age effects in event-based PM

systematically varied as a function of task order specificity. In detail, PM age effects were larger in specified compared to unspecified PM tasks. Furthermore, confirming prior findings, an effect of cue focality with larger PM age effects in nonfocal compared to focal PM tasks was found. Tests of homogeneity showed that these moderator variables explained a significant proportion of variance across observed PM age effects.

The present finding of larger age effects in specified (compared to unspecified) PM tasks is in line with evidence that higher demands on cognitive control are associated with larger PM age effects (e.g., Kliegel et al., 2008b; Schnitzspahn et al., 2012b). When

considering the cognitive processes that occur immediately after successful PM cue detection in specified PM tasks, participants must navigate between the PM and ongoing task response options and decide on the correct order. Cognitive control is necessary to manage this

situation as a particular response order is required. In comparison, there is a higher degree of freedom of response management in unspecified PM tasks as one is flexible which response is made first, and this seems to pose fewer problems to older adults (see Section 7.2.4.1, for a more detailed illustration of possible underlying mechanisms). Clearly, future research will have to study the exact nature of the processes involved in more detail (see Section 7.3.2, for an outlook). It could be argued that these unspecified tasks are simply easier and therefore might affect PM performance in general and that the present results might be due to ceiling-effects in younger adults. However, analyses showed that there was no evidence of such a potential confounding effect.

Concerning the effect of cue focality, the present results are in line with the proposal of the multiprocess framework that PM age effects should be larger in nonfocal than in focal

PM tasks due to a higher degree of controlled, strategic cognitive processes necessary in nonfocal tasks to detect PM cues (McDaniel & Einstein, 2000; McDaniel et al., 2008; Rendell et al., 2007; see Section 7.2.4.1, for a more detailed illustration of possible underlying

mechanisms). This confirms prior meta-analytic results (Kliegel et al., 2008c). Clearly, future research will have to study the exact nature of the processes involved in more detail (see Section 7.3.2, for an outlook).

Taken together, the present meta-analytic findings suggest that both task order

specificity and cue focality are important factors in the light of PM age effects. These findings will be discussed with respect to a broader conceptual perspective in Section 7.2.2.

7.1.3 Are adult age differences in laboratory PM attributable to age differences in stress level? (Study 3)

The third research question can clearly be answered with “no”. Results from Study 3 (see Chapter 6) showed that the age deficit in PM performance was confirmed with present data. However, older adults did not show higher stress levels compared to younger adults at any time during the experiment. Furthermore, stress level did not show a significant

association with PM (or ongoing task) performance. Concerning the relaxation intervention, stress levels were successfully reduced. Yet, the intervention had neither an effect on PM (or ongoing task) performance in general nor on the age deficit. All in all, present data suggest that stress plays a minor role in the context of laboratory PM.

In light of the evidence that stress seems to impair a variety of cognitive functions such as attentional control and working memory, the present finding of no association between stress level and PM does not support this general view. However, the literature on stress effects on PM performance is mixed: While there is evidence from naturalistic PM in younger and older adults for a negative association of perceived stress and PM (e.g.,

Schnitzspahn et al., 2011), Nater et al. (2006) found a positive effect of stress on time-based laboratory PM in younger adults. However, Nater et al. found no effect on event-based PM.

Also studying younger adults only, Nakayama et al. (2005) found as well no association of stress level with event-based PM performance. Hence, considering these latter two results from laboratory studies, which are in line with the present findings, it could be suggested that stress plays a rather small role in the context of laboratory PM. Moreover, the present findings do not support the suggestions of Sindi et al. (2013) that memory age deficits usually found in laboratory settings could be caused by increased stress in older adults; at least for a traditional time-based PM task.

Taken together, the present findings suggest that individual levels of stress play a minor role in explaining individual and age differences in laboratory PM. These findings will be discussed with respect to a broader conceptual perspective in Section 7.2.3.