Mechanisms of adult age differences in naturalistic PM

Reviewing the evidence on the age PM paradox, Phillips, Henry, and Martin (2008) summarized various factors that have been discussed in the literature as possible causes for the paradoxical pattern. Concerning the naturalistic setting, they supposed that older adults’

higher PM performance may be attributable to their larger experience with real-world PM tasks, with own memory failures, and with individual time management which may have resulted in the development and use of compensatory strategies to aid the fulfillment of intentions (Maylor, 1996b). Similarly, it is considered that older adults may have greater metacognitive awareness of how to achieve to remember to execute the future task (e.g., Schnitzspahn et al., 2011). Furthermore, it is hypothesized that age differences in attitudes to punctuality and in personality dimensions such as conscientiousness may cause age

differences in naturalistic PM (e.g., Dobbs & Reeves, 1996). Besides that, three other often suggested mechanisms, which are motivational aspects, the use of reminders, and everyday stress were of particular interest for the present work and are therefore described in more detail in this section.

Beyond these many factors discussed, Phillips et al. (2008) underlined the urgent need for studying age differences in naturalistic PM tasks that have high ecological validity, since research on this type of PM could give further important insights into the paradox. They differentiate between artificial tasks externally provided by an experimenter such as calling or posting messages to an experimenter at pre-specified times and “real” naturalistic PM tasks, which naturally occur in everyday life without interference of an experimenter such as keeping appointments, paying a bill in time, or calling a friend at his birthday. Although such

real life PM examples are often cited in the literature when introducing PM, so far, studies exploring age benefits in naturalistic PM tasks have focused on the artificial experimenter-given task type, and there is surprisingly little known about age-related PM in the real life.

The few PM studies achieving high ecological validity were using medication adherence as the critical task. However, while some studies found that medication compliance is higher in older compared to younger adults (Schulz, O’Donnell, McDonough, Sasane, & Meyer, 2005;

Park et al., 1999), other studies reported an age deficit (Roe, Motheral, Teitelbaum, & Rich, 2000), or no age effect (Lorenc & Branthwaite, 1993). Phillips et al. argued that this

heterogeneity of results may be due to medication adherence being clearly dependent on many other social, physical, and cognitive factors and on the type of medication itself. Beyond that, they emphasized that it would be of interest to know more about everyday PM with a larger variety of intentions in younger and older adults. With regard to the very few and

inconclusive results in this context, it remains an open question whether the age benefit observed in experimenter-given naturalistic PM tasks generalizes to PM tasks naturally occurring in participants’ everyday life. Hence, the major focus of Study 1 was to clarify this important issue.

With regard to motivational aspects, one debated explanation is that older adults may be more motivated to successfully complete PM tasks that are implemented in their everyday life (Moscovitch, 1982; Patton & Meit, 1993; Rendell & Craik, 2000). In comparison, the level of motivation of younger participants to complete PM tasks among the other demands of everyday life may be relatively low. This is particularly likely to be the case for

undergraduate students completing studies for course credits, who represent the majority of younger participants in typical PM studies (Maylor, 1993b). Although this explanation is very widespread, systematic research on this topic is sparse. In a first study directly examining the motivational angle in experimenter-given naturalistic PM tasks in younger and older adults, Aberle, Rendell, Rose, McDaniel, and Kliegel (2010) used a monetary incentive to

manipulate motivation. Results showed that this improved only younger adults, who then reached the performance level of older adults supporting low motivation as an explanation for younger adults’ inferior performance in naturalistic PM tasks. Further evidence comes from a recent study showing that higher a priori ratings of motivation to perform an experimenter-given naturalistic PM task in the older adults were correlated to subsequent higher PM performance (Schnitzspahn et al., 2011). Besides this first indication that motivational level contributes to age differences in naturalistic PM, it remains an open question whether this mechanism holds also for PM tasks naturally occurring in the everyday life of the participants.

A possibly important indication in this context could be a mechanism, which has been suggested as influential for real life PM performance in a study from Marsh, Hicks, and Landau (1998) focusing on younger adults only. They showed that younger adults realized important real life intentions more frequently than less important ones suggesting that important tasks raise the motivation for correct fulfillment. Study 1 set out to further investigate whether this mechanism found in younger adults could contribute to age differences in real life PM.

Another popular explanation for age benefits in naturalistic PM tasks is that older adults may use more external reminders such as a note in a calendar to cue PM retrieval (Phillips et al., 2008). Available results concerning the use of reminders in younger and older adults in naturalistic PM tasks are however mixed (Maylor, 1996b; Patton & Meit, 1993): In some studies with PM age benefits, older adults reported using more reminders (e.g., Jackson, Bogers, & Kerstholt, 1988), whereas in other studies, the younger ones reported more

frequent use of reminders (e.g., Dobbs & Rule, 1987; Rendell & Thompson, 1999). Rendell and Craik (2000) instructed participants not to use reminders in a naturalistic PM task. In a post-task debriefing interview, both younger and older participants reported generally low use of reminder strategies, whereas an age benefit in PM performance was still present. Moreover, Rendell and Thompson (1999) found that providing both age groups with an alarm in one

condition and in another condition with instructions and the opportunity to link cues from their environment to the prospective action did not reduce the magnitude of the older adults’

superiority compared to younger adults in the naturalistic PM task. In line with these results, Phillips et al. (2008) concluded that there is remarkably little evidence supporting the popular idea that age benefits in naturalistic PM are caused by increased use of reminders. However, studies on naturalistic PM in younger and older adults concentrated on comparing both age groups with regard to PM performance and use of reminders on a group level and did not focus on possible direct associations of individual use of reminders with subsequent individual PM performance. In a study on naturalistic PM in older adults only, Maylor

(1990a) showed that those participants who used external reminders were more likely to fulfill the intended action than those relying only on internal cues (i.e., that the intention pops into mind on its own). Within this sample of older adults only, there was no age effect on PM performance. However, among those participants who used external memory cues, age was positively associated with PM performance, whereas in the minority of participants who relied only on internal cues, age was negatively associated with PM. Hence, it remains unclear whether there is a direct association of the use of reminders and PM performance on an individual level across different adult age groups and whether this explains age differences in naturalistic PM. A further open question concerns whether the use of reminders might

contribute particularly to age differences in real life PM. There, especially older adults may be more aware of their need for using reminders to aid the fulfillment of intentions. This

suggestion is supported by the finding that older adults seem to have greater knowledge of successfully using supportive strategies in terms of metacognitive awareness (Schnitzspahn et al., 2011). Hence, in the light of these open questions, Study 1 set out to further explore the impact of use of reminders on adult age differences in everyday PM.

A further common explanation for age benefits in naturalistic PM performance is that, compared to older adults, the life of younger adults is less structured, less predictable, more

engaging, and busier (e.g., Henry et al., 2004; Maylor, 1996b; Rabbitt, 1996). Similarly, it is suggested that older adults have less distraction due to fewer occupations and daily activities through their retirement. This is an important issue since in most PM studies, younger adult university students are compared with retired older adults. Taken together, the suggested underlying mechanism is that older adults may be less stressed than younger adults and therefore can implement delayed intentions more accurately. However, findings regarding potential stress effects on naturalistic PM performance are inconclusive. On one hand, Rendell and Thompson (1999) found no difference in naturalistic PM performance between working and retired older adults. On the other hand, Schnitzspahn et al. (2011) observed that younger adults reported significantly more perceived everyday stress than older adults and everyday stress mediated age-related variance in the naturalistic PM task. Given the heterogeneity of previous results regarding the role of everyday stress in age-related PM performance, Study 1 aimed to further explore this issue. To clarify the role of stress also in the laboratory setting, Study 3 used an experimental approach to evaluate this issue in laboratory PM.

Taken together, various factors have been proposed to explain the age benefit in the naturalistic setting but previous results concern single aspects only, are heterogeneous and so far inconclusive. Therefore, the focus of Study 1 was to further investigate the impact of motivational aspects, use of reminders, and everyday stress on adult age differences in everyday PM performance using real life PM tasks with high ecological validity.