Adult age differences in PM - Alternative mechanisms

As individual and age-related differences in PM are not entirely accounted for by other cognitive abilities, it is an interesting question which further factors are involved and how they determine PM age differences. For example, it is of interest whether confounding mechanisms may potentially contribute to PM age differences. Some of those “alternative”

explanations will be outlined in the following. For example, it is argued that characteristics of the testing situation per se may contribute to adult age differences in cognitive performance (Sindi et al., 2013). Specifically, Sindi et al. argue that the novelty and unpredictability of certain characteristics of the testing situation per se cause a physiological stress response in older adults that thereby impairs their cognitive performance. This suggestion is in line with studies showing that physiological stress impairs cognitive functioning (e.g., Lee et al., 2007;

Liston et al., 2009) and links those effect to the laboratory test setting typically used in cognitive aging research. That novelty and unpredictability of test characteristics cause stress could for example be the case when the location of testing is unfamiliar for older adults (Sindi et al., 2013): Laboratory testings often take place at the university, which is more familiar for younger than for older adults. Sindi et al. argue that this novelty evokes stress particularly in older adults that impairs their performance and thereby increases age deficits in cognitive test performance. Furthermore, it is debated that younger adults (who are often students

participating for course credit) have greater experience with laboratory testing situations and with performing cognitive tests. In contrast, these testing procedures are more novel for older adults. Again, this novelty and lack of experience could impair older adults’ performance (Phillips et al., 2008), especially through detrimental stress effects (Sindi et al., 2013).

However, Study 3 (see Chapter 6) did not find increased stress levels in older adults in a typical laboratory testing situation (i.e., that took place at the university and contained

cognitive tasks that were unfamiliar for older adults). Furthermore, the PM age deficit was not related to individual stress level. Hence, these findings from Study 3 suggest that - if the

nature of the laboratory setting per se should evoke the PM age deficit - this seems not to be due to increased levels of stress in older adults. In other words, concluded from Study 3, increased stress evoked by the testing situation per se seems unlikely as a potential alternative explanation for the PM age deficit. It has to be noted that research to systematically

investigate potential confounding mechanisms in PM age differences is still in its infancy.

Hence, it remains an open question whether other characteristics of the testing environment affect PM age differences. Thus, future research is needed to explore those potential

confounding effects.

This may concern the time of testing (e.g., morning/afternoon) and task instructions (e.g., strong/weak emphasize on certain cognitive aspects of the task) as those characteristics of the testing situation per se may contribute to adult age differences in cognitive performance (Sindi et al., 2013). Specifically, regarding the time of testing, it is reported that the optimal time for older adults is in the morning, while for younger adults the optimal time is in the afternoon (e.g., May & Hasher, 1998). There is evidence that when older adults are tested in the afternoon, their performance is significantly worse compared to younger adults. In

contrast, when they are tested in the morning, their performance does not differ (e.g., Borella, Ludwig, Dirk, & de Ribaupierre, 2011). Particularly retrospective memory, working memory, and inhibition are affected by a non-optimal time of testing (Borella et al., 2011; May &

Hasher, 1998). Hence, as these cognitive abilities are associated with successful prospective remembering (for details, see Section 7.2.4.1 for an analysis of the different processes required in prospective remembering and their vulnerability to impairments in associated cognitive abilities), this suggests that older adults may be impaired in PM when been tested during their non-optimal testing time. However, at this point this has to remain speculative as no study so far has examined the effect of time of testing on adult age differences in PM. Yet, it should at least be considered that PM studies may overestimate age deficits when testing

older adults during their non-optimal testing time. Future studies could code the time of day as a control variable and analyze whether this has affected the results.

Furthermore, there is evidence that certain task instructions can impact older adults’

retrospective memory performance. When task instructions emphasize the memory

component (e.g., simply by several mentioning that something has to be remembered), older adults show a lower performance. This may be because older adults believe that their memory abilities have deteriorated (e.g., Rahhal, Hasher, & Colcombe, 2001). Rahhal et al. (2001) further demonstrated that age differences were obtained when the instructions emphasized the memory component of the task but not when the instructions did not emphasize memory. This suggests that aspects of the testing situation, such as “unfavorable” experimental instructions, may lead to an overestimation of age deficits in retrospective memory performance. In PM task instructions, it is often noted that there is an interest in participants’ ability to remember to perform an action in the future (e.g., Marsh, Hicks, Cook, & Mayhorn, 2007). Hence, it could be argued that such remarks emphasize the memory component in PM tasks and that this increases PM age deficits. However, the impression of older adults that the task would be difficult for them (e.g., because of the memory component) could as well increase the

personal importance to overcome their supposed memory problems and to perform well on the task. This may result in a relatively good PM performance in older adults and thereby in a decreased age deficit (e.g., Altgassen et al., 2010a). As no study so far has directly examined this issue, it remains an open question whether typical PM instructions (that do not aim to highlight difficulties of the PM task) involuntarily emphasize the memory component (or other demanding features) of the PM task and whether this impairs older adults’ PM performance and thereby increases PM age deficits.

Another confounding factor associated with the testing procedure per se that may affect PM age differences could be stereotype threat in older adults. Stereotype threat in general refers to the concern that one’s performance may confirm a negative stereotype about

the abilities of one’s group (Steele, 1997). Specifically, age-related stereotypes predict that all individuals experience a severe cognitive decline in older age (Hess, 2005). In fact, there is evidence that age stereotype threat impairs retrospective memory performance (e.g.,

Chasteen, Bhattacharyya, Horhota, Tam, & Hasher, 2005). Note that in contrast to the aforementioned detrimental effects of emphasizing certain cognitive aspects of the task, age stereotype threat can affect older adults’ cognitive performance even when those cognitive aspects are not emphasized in the instructions (e.g., Mazerolle, Regner, Morisset, Rigalleau,

& Huguet, 2012). Specifically, Mazerolle et al. (2012) underlined that all manifestations of age stereotype threat in their study were obtained by simply informing older (and younger) adults about the presence of younger (and older) participants without emphasizing any demands of the task. Furthermore, it has been shown that reduced age stereotype threat is associated with reduced or even eliminated age differences in retrospective memory

performance (Desrichard & Köpetz, 2005; Hess, Auman, Colcombe, & Rahhal, 2003). Hence, age stereotype threat seems an important aspect in cognitive testing procedures when

comparing younger and older adults.

For example, Mazerolle et al. (2012) conducted a study to examine effects of age stereotype threat on working memory performance. 110 younger adults (mean age = 21.35 years) and 110 older adults (mean age = 69.01 years) performed a pre-test of working memory. Then, both younger and older adults were randomly assigned to one of the two following conditions: In the age stereotype threat condition, each participant was simply told that both younger and older adults were participating in the study. In the reduced threat condition, the same information was given, but each participant was also told that

performance on the examined tasks usually does not differ between younger and older adults (i.e., that the tests were age fair). After that, the post-test of working memory was assessed.

Participants’ performance in the second working memory task was examined using an

analysis of covariance, controlling for performance in the first working memory task. Results

showed that younger adults outperformed their older counterparts. In addition, participants performed better in the reduced age stereotype threat condition than in the threat condition.

Importantly, an interaction of Test Instruction with Age Group was revealed. Comparisons between the subgroups showed that older adults performed worse in the age stereotype threat condition than in the reduced threat condition, whereas younger adults performed equally well in both conditions. Furthermore, older adults performed worse than younger adults in the age stereotype threat condition, whereas both age groups performed equally well in the reduced threat condition. In sum, Mazerolle et al. (2012) provided evidence that age stereotype threat consumes working memory resources in older adults. This could be critical in PM: From an analysis of the different processes involved in prospective remembering, working memory is required for processing the background activity and simultaneously monitor for PM cues. In addition, retrospective memory is required to conserve the content of the intention and is thus necessary for proper encoding end retrieval of the intention (for details, see Section 7.2.4.1 for an analysis of the different processes required in prospective remembering and their

vulnerability to impairments in associated cognitive abilities). Hence, as PM requires proper functioning of several cognitive processes, an impairment of involved cognitive abilities such as working memory and retrospective memory in older adults through age stereotype threat (as reported by e.g. Chasteen et al., 2005; Mazerolle et al., 2012) could possibly evoke (or increase) age deficits in laboratory PM. However, as no study so far has directly examined this issue, it remains an open question whether age stereotype threat impairs older adults’ PM performance and thereby increases PM age deficits. Hence, future research is needed to clarify those potential confounding mechanisms. In Section 7.3.3, an exemplary outlook for a study examining the effects of age stereotype threat on age-related PM performance is given.