Discussion

As research on age-related PM performance in everyday life is very rare, the present study set out to explore PM performance in naturally occurring PM tasks over the time course of one week. The first aim of the present study was to examine whether age-related benefits in naturalistic PM tasks also hold for naturally occurring everyday PM tasks that were formed and intended by the participants and not imposed on them by an experimenter. Here, the data clearly showed that older adults outperformed younger adults in realizing their intentions.

This result corroborates the conclusions of Henry et al. (2004) that older adults generally show better PM performance in naturalistic settings and critically extends previous research by being the first study to demonstrate the validity of the PM age benefit in naturalistic settings beyond experimenter-given and more or less artificial naturalistic tasks. Thus, one key question for future research will be to delineate the reasons behind this pattern.

To stimulate this possible future line of research, as a second aim, several factors that may be associated with age effects in everyday PM were explored. First, the role of personal task importance was examined. As predicted, there was a significant 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 the predicted perfect 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. In contrast to Aberle et al. (2010), however, in the present study personal importance also affected older adults’ performance; yet, only in terms of a performance increase from the lowest to the medium level of importance. Older adults were almost perfect in the two upper levels of importance while younger adults almost showed a

linear increase across the three importance levels and only reached perfect performance and thereby older adults’ performance level for the very important intentions. This may hint at two critical age or cohort differences: First, Aberle et al. used external monetary incentives to manipulate the general level of motivation to perform the PM task and the present study assessed the personal relevance on an individual task level. Thus, importance was task-inherent in the present study and externally motivated in Aberle et al. and this seems to suggest that older adults may not respond to external incentives in general or monetary

incentives in particular as much as younger adults (but see Touron, Swaim, & Hertzog, 2007).

Second, there may be age or cohort differences in perceiving the suggested meaning of the importance labels offered in the interview. There is evidence that older adults are more conscientious than younger adults and some researchers suggested that this may be associated with better PM performance, particularly in naturalistic settings (see Phillips et al., 2008, for an overview). In the present study, this may have resulted in older adults perceiving their intentions more obligatory after they had told them to the experimenter. This may have been exacerbated by the experimenter daily calling the participants. This means that for older adults, ‘wanting to do something’ may be more similar to ‘having to do something’ than it is for younger adults; but this has to remain speculative at this point. Note that although

importance ratings were subjective those ratings had to be given a priori in the planning phase before execution. Thus, participants could not simply post hoc downgrade those intentions they may have forgotten. It has to be also noted that the largest age effect was actually found for the medium important plan category and not for the lowest one, as one could expect if older adults were more cooperative.

It should be acknowledged that in this exploratory study, we did not explore the contents of the plans, but just asked how important the plan was for the person on a subjective level as Marsh et al. (1998) did. Future research needs to investigate whether PM task features vary according to level of importance and between younger and older age groups. Possible

task features include the extent a task is habitual, and others are whether a PM task is event- or time-based. In any case, taken together, current results clearly argue in favor of personal importance being an important moderator of age-related PM performance and previous

studies on experimenter-given naturalistic PM performance may have underestimated younger adults’ PM performance as the tasks given may have differed in perceived importance across age groups. Future studies will thus have to directly target the motivational and cognitive mechanisms of these effects. One avenue in this regard may be to experimentally vary importance levels and examine the effects on prospective and ongoing task performance as it has been done in younger adults (see Kliegel, Martin, McDaniel, & Einstein, 2001, 2004).

The second factor tested that may be associated with age effects in everyday PM was the use of reminders. Yet, while this was found as contributing to PM performance in general, use of reminders did not interact with the age benefit in PM performance; there was no age-related use of reminders to start with, although use of reminders did increase somewhat with increasing importance of PM tasks. This suggests that - in real life intentions - younger and older adults do make use of reminders but not differentially so. Both age groups substantially increased the use of reminders if an intention was very important and both age groups’

performance profited from the employment of reminders; yet, this factor does not seem to explain the age benefit observed. It is acknowledged that this study was limited to the assessment of a mean level of use of reminders aggregated over the five study days and thus future research needs to examine the various types of reminders and the relationship between use of reminders and success on specific PM tasks. While it has to remain an open question at that point, whether the reminders used in general and in different age groups particularly may differ in qualitative terms and with regard to their efficiency, current data speak against the popular view of reminder use being behind the age benefit and corroborate previous studies on experimenter-given naturalistic PM tasks showing that the use of reminders cannot explain

age-related PM performance in the field (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). However, the age benefit was not explained by everyday stress; in fact, the current study did not observe age differences in levels of perceived stress to start with. This suggests that it is unlikely that age-related naturalistic PM performance may be caused by different levels of everyday stress;

even when comparing students with retired older adults as in the present study. It has to be acknowledged though that the level of stress was assessed only on a very global scale and aggregated across the entire week. Thus, the current data cannot rule out the possibility that fluctuations of perceived stress across more or less busy days may interact with fluctuations in PM performance on a more fine-grained scale which should be examined in future research.

The available data, however, do not lend support for the differential stress hypothesis of the age benefit in naturalistic PM performance.

Drawing preliminary conclusions on the role of the three possible mechanisms that were derived from the literature, personal importance could be confirmed as interacting with the age benefit while stress and reminders did not receive empirical support from the present data. Besides those results, some additional results emerged from a more detailed analysis of participants’ intention formation and completion reports in the daily interviews that were not expected a priori. We acknowledge that these results are clearly exploratory and as we did not have any predictions in those regards, they need to be interpreted with caution. Yet, they may add some first insights to the understudied area of age differences in everyday intention formation and realization of intended actions across adulthood and thus may stimulate future research more thoroughly examining those results.

A first result deserving attention was that overall younger adults had more intentions for the following day than older adults. This may suggest that older adults are more

conservative in either forming intentions and/or reporting those; possibly due to their

metacognitive awareness of their memory fallibility. Thus, one may argue that it might not be surprising that younger adults have lower PM performance in the field because they have more tasks to remember to start with. However, present data showed that number of intentions did not predict PM performance in general and was not related to the age effect in particular.

Thus, the observation that younger adults generally had more intentions to be remembered on the following day could not explain age-related PM performance in the present study.

There was another aspect of participants’ self reports in the interviews that caught our attention: the reprioritization of intentions. Older adults reported much more often that they had consciously decided to change and reschedule intentions. Moreover, reprioritizing was strongly related to PM performance and the observed age effect. On first glance one may argue that it is somewhat trivial that the age effect in performance (intention completion) is eliminated when one of the two major categories of non-completion (intention forgetting and reprioritizing) is taken into account. However, note that PM performance ratio was only calculated after excluding those intentions that were reprioritized (see also footnote 2;

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 PM forgetting of intended actions.

One may still argue that due to stereotype threat effects or reporting biases older adults may have just told us at the end of the day more often than younger adults that they had reprioritized their intentions although in fact they had forgotten them. As with any diary study, we cannot exclude this possibility but as indicated in the methods section the protocol was designed to avoiding this response bias and required neutral reporting of reasons for non-completion in an open question not using labels such as forgetting or memory failure.

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. Related to those issues, one may note that even when considering the general caveats of self-report data, this approach appears to be a valid procedure when studying the topic of interest; everyday PM behavior without providing participants with any externally given tasks. Moreover, the methodology suggested to apply in this line of research by Marsh et al. (1998) was critically improved in the present study. Here, completion of intentions as well as variables possible affecting age-related PM performance were recorded on a daily basis and by phoning the participants to minimize retrospective errors and reporting biases.

The primary aim of the present study was to find out more about real life PM, not to compare tasks in naturalistic studies with real life PM tasks. However, it is acknowledged that in previous naturalistic studies, punctuality has often been the focus with tasks required to be completed at set times (e.g., logging time in Rendell & Thompson, 1999), but not in all studies (e.g., mailing post cards, Patton & Meit, 1993). In Rendell and Thompson (1999) punctuality played a role for younger adults with the finding that younger adults were more often late and when late they were much later than older adults. Punctuality did not play a role in the present study as the planned intentions did not require a specific point in time for their realization. Thus, we were not able to report if a failure to complete a task at the initially intended time might partially reflect being late and this is something for future research to consider. However, it is interesting that in the present study we have found an age-related benefit even when the punctuality demands were not high. Future research should investigate whether age-related benefits vary according to different punctuality demands and in particular whether real life PM tasks are event or time-based.

In closing, two issues that may be conceptually of interest shall be noted. One is the added value of distinguishing forgetting and reprioritizing intended actions. One could argue that in both cases the previously intended action has not been completed the next day and thus, it may appear that younger adults still implement their intentions as effectively as older

adults. Yet, as one critical advantage, reprioritizing allows for taking measures to avoid negative consequences of non-completed intentions such as calling a friend that one will not make the appointment. Taken together, present data appear to suggest that older adults may actively review their everyday PM tasks more often or more systematically and may insert a replanning phase after the initial intention formation; a process component that has so far not been studied in PM research but may be an important aspect of everyday PM.

To put the present data in a broader conceptual context, these observations are in line with the model of selective optimization with compensation (Baltes & Baltes, 1989). In this model, one of the major adaptive processes in successful aging is the selection of e.g.

alternative actions as well as action- and emotion-regulation by re-setting preferences. Thus, these processes appear to be also at work in PM as older adults seem to optimize the

realization of their intentions by adapting consciously to changing situational constraints and to limited time resources in daily life. It can be assumed that older adults have more

experience in reprioritizing and have gained effective strategies to deal with limited time and conflicting intentions. An alternative explanation of course may be that reprioritization of intentions might be less conscious in younger adults. It can be speculated, that younger adults may want to maintain flexibility in completing intentions and thus refrain from cancelling them. Again, future work will have to directly study those cognitive and motivational processes in detail.

In sum, the present exploratory study is the first to show that age benefits in PM performance in the field transfers to real life PM tasks and beyond artificial, experimenter-given tasks. Personal importance emerged as a particularly relevant moderator of the age benefit. Unexpectedly, reprioritization of intentions was another factor that appeared to be associated with the age benefit. This suggests that traditional conceptual models of

gerontology describing goal setting and processes of developmental regulation may be

important to consider also in theory-building of everyday cognition such as naturalistic PM performance.

5. Study 2: Investigating the impact of task order specificity on