Aging ebbs the flow of thought: Adult age differences in mind wandering, executive control, and self-evaluation
Highlights
► Two experiments test for age differences in mind-wandering during cognitive tasks. ► Older adults show reduced rates of task-unrelated thought. ► Older adults show increased rates of performance-related thought. ► Findings are not easily accommodated by executive-resource theories of mind-wandering.
Introduction
Young adults spend, on average, a third to half of their daily lives thinking about something other than their current activity (Kane et al., 2007, Killingsworth and Gilbert, 2010, Klinger and Cox, 1987–1988, McVay et al., 2009). Unfortunately, these task-unrelated thoughts (TUTs) can sometimes result in “absentminded” mistakes (e.g., McVay et al., 2009, Reason, 1990, Schooler et al., 2004, Smallwood et al., 2004). Mind wandering is thus a frequent, yet occasionally costly, experience. It also occurs more frequently for some people than others: college students who have poorer cognitive-control abilities, such as those with lower working memory capacity (WMC; Kane et al., 2007, McVay and Kane, 2009, McVay and Kane, 2012a) and attention deficit/hyperactivity disorder (AD/HD; McVay et al., 2008, Shaw and Giambra, 1993), report more TUTs during challenging tasks than do people with better control abilities.
As we age, then, does the propensity to mind-wander increase? Do TUTs account, in part, for older adults' performance deficits in many tasks involving cognitive control? Based on age-related decline in many domains, including WMC (see Craik & Salthouse, 2008), and on theoretical accounts that propose deficits in goal maintenance or attentional inhibition to explain age differences in executive control (e.g., Braver and West, 2008, Hasher and Zacks, 1988), we might expect that older adults are often mind wandering. For example, the Braver–West view claims that older adults have difficulty maintaining task-related goals to intentionally guide actions; an age-related inability to keep task-irrelevant information from becoming conscious (as TUTs) should thus disrupt active maintenance or accessibility of task goals, thereby leading to errors. Indeed, Hasher and Zacks originally theorized that such impaired inhibition is the root of much age-related variance in cognition (see Hasher et al., 2007, Hasher et al., 1999).
Counter to this prediction, however, and in contrast to most WMC-related findings with younger adults (e.g., Kane et al., 2007, McVay and Kane, 2009; but see Levinson, Smallwood, & Davidson, 2012), older adults actually report less frequent TUTs than do younger adults (Giambra, 1989, Grodsky and Giambra, 1990–91, Jackson and Balota, 2012; Krawietz, Tamplin, & Radvansky, in press). The negative correlation between age and mind-wandering rate was first established via retrospective questionnaires (e.g., Giambra, 1977–78, Singer and McCraven, 1961), and may have reflected age-related memory or metacognitive deficits, or a reporting bias. To demonstrate aging's effect on mind wandering in a controlled setting, Giambra (1989) measured TUTs during a laboratory vigilance task with instructions aimed to encourage reporting and to limit self-censure. Across five experiments, older adults reported fewer TUTs than did younger adults.
Giambra's (1989) findings are surprising from the perspective that aging impairs executive control and that executive-control failures predict TUTs. Indeed, Giambra discussed these results as contradicting the Hasher and Zacks (1988) view that older adults have decreased inhibitory ability. Giambra argued, instead, that TUTs represent trains of thoughts, or “unfinished business,” which come to a conclusion during unconscious processing and then require attentional capacity to enter awareness. In other words, when performing a task that does not require full attention, excess attentional capacity can be devoted to mind wandering. Accordingly, younger adults should experience more TUTs than should older adults because they have more attentional capacity and more often an excess to allow TUTs. Giambra further explained, however, that his tasks were designed to allow plenty of attentional capacity to spare (supported by ceiling-level performance), and proposed that older adults have less “unfinished business” than do younger adults, leading to fewer and less urgent unconscious thoughts.
Giambra (1989) thus foreshadowed a current debate about the role of executive resources in TUTs. The Smallwood and Schooler (2006) theory of mind wandering characterizes TUTs as requiring the resources typically used for executive control (see also Teasdale et al., 1995), with evidence drawn from studies showing that: (1) tasks imposing greater cognitive loads reduce TUT rates (e.g., Antrobus, 1968, Teasdale et al., 1993, Teasdale et al., 1995) and, conversely, practice-driven automaticity increases TUT rates (e.g., Mason et al., 2007, Teasdale et al., 1995); (2) executive-control brain networks, along with “default mode” networks, are active during mind wandering (e.g., Christoff, Gordon, Smallwood, Smith, & Schooler, 2009); (3) in-the-moment TUT reports predict performance errors, suggesting competition for a unitary processing capacity (e.g., Smallwood et al., 2004); (4) individual differences in control capabilities may be positively associated with TUT rates during very simple tasks, such as breath monitoring, indicating that people with more available resources use them to mind-wander (Levinson et al., 2012, but see McVay and Kane, 2012a, McVay and Kane, 2012b).
McVay and Kane (2010a), in contrast, propose a “control failures × current concerns” view that takes the opposite stance on the role of executive capacity: the contents of TUTs are automatically and continuously generated unconsciously in response to environmental cues to subjects' current concerns and goals (following Klinger, 1971, Klinger, 1999, Klinger, 2009), similar to Giambra's concept of “unfinished business.” Cued TUTs then enter awareness as a result of an executive-control failure, as opposed to the availability of excess capacity. Their main sources of evidence were: (1) TUTs predict performance deficits on attention-demanding tasks (e.g., McVay and Kane, 2009, McVay et al., 2009, Smallwood et al., 2004), which may indicate that TUTs enter awareness when control falters, rather than when there is capacity to spare; (2) contexts that impair control abilities, such as fatigue (e.g., Antrobus et al., 1966, McVay and Kane, 2009, Smallwood et al., 2004, Smallwood et al., 2005; Teasdale et al., 1995) and inebriation (Finnigan et al., 2007, Sayette et al., 2009), increase TUTs; (3) individual differences in control are negatively associated with TUT rates during demanding tasks (e.g., McVay and Kane, 2009, McVay and Kane, 2012a, McVay and Kane, 2012b, Shaw and Giambra, 1993); (4) subjects who have greater attention control suffer as much performance cost as those with poorer control on occasions when they experience TUTs, in conflict with a resource-availability view that predicts spare resources to minimize dual-tasking costs.1
Giambra's (1989) findings of TUTs decreasing with age seem to fit more comfortably with the executive-resource view of mind wandering than the control failures × concerns view. Older adults, who have reduced WMC (Bopp & Verhaeghen, 2005) and poorer attention control (e.g., Cohn et al., 1984, Hamm and Hasher, 1992, Hartley, 1993, Spieler et al., 1996, West and Baylis, 1998), should experience more control failures than should younger adults. If control failures drive mind-wandering, then older adults should mind-wander more frequently. Thus, older adults' reduced rate of mind-wandering seems to suggest, instead, that they have insufficient resources to maintain TUTs in the face of simultaneous tasks. Given the potential importance of aging findings to general theories of mind-wandering, we thought it necessary to confirm and expand on Giambra's results. In the current study, we improve upon Giambra's methods and address an alternative explanation for the age-related differences in TUTs he found.
Although Giambra's (1989) laboratory studies improved upon retrospective surveys of mind-wandering tendencies, he asked subjects whether they had experienced any TUTs during 25–30 s task periods, a long enough delay to allow forgetting or confabulation. In our studies, as is now common (Smallwood & Schooler, 2006), we further reduced retrospective biases by probing subjects randomly throughout the task and having them report on their immediately preceding thoughts. In addition, Giambra's vigilance tasks yielded ceiling performance, which prevented assessment of TUT–performance associations (which bears on whether TUTs draw on executive resources). The current studies kept performance below ceiling to allow tests of whether in-the-moment costs of TUTs were similar across age groups.
While we were conducting the current studies, both Jackson and Balota (2012) and Krawietz et al. (in press) similarly reported age-related decreases in TUTs. Moreover, they did so using random, in-the-moment thought probes (like ours) during variations of a go/no-go task (the “sustained attention to response task” [SART]; Jackson & Balota, 2012) or reading comprehension tasks (Jackson & Balota, 2012; Krawietz et al., in press). Although Jackson and Balota did not assess age differences in the consequences of TUTs for performance, Krawietz et al. reported that both older and younger adults were similarly inaccurate in answering reading comprehension questions following TUT reports versus on-task-thought reports; moreover, Krawietz et al. found age differences in TUT rates within tasks that yielded either no age differences in accuracy (Experiment 1) or significant age differences in accuracy favoring younger adults (Experiment 2). A growing body of data thus points consistently to reduced TUT rates in older versus younger adults, regardless of age differences in corresponding task performance.
The primary purpose of our study was to test an alternative explanation for age differences in TUT rates by probing for a particular thought category. In our previous young–adult work (McVay and Kane, 2009, McVay and Kane, 2012a), subjects reported not only on-task thoughts versus TUTs, but also evaluative thoughts about their performance (e.g., “I'm good at this!”; “I'm screwing up.”), or so-called “task-related interference” (TRI; e.g., Smallwood et al., 2004; see also Mikulincer and Nizan, 1988, Sarason, 1988). TRI differs conceptually from TUTs because it is, in a sense, task-related; however, TRI experiences are also not quite “on-task,” or directly about the task stimuli or demands, either. TRI is also empirically distinguishable from both TUTs and on-task thoughts. On one hand, TRI and on-task thoughts both decline with time on go/no-go tasks, while TUTs increase (McVay and Kane, 2009, McVay and Kane, 2012a). On the other hand, TRI and TUTs are similarly associated with higher in-the-moment go/no-go errors than are on-task reports (McVay & Kane, 2012a). Note that the control failures × concerns view argues that mind-wandering propensity reflects an interaction of control abilities and the cuing of personal goal-related concerns. Although typical laboratory contexts, with computer equipment and young–adult researchers in campus buildings, are less likely to cue many of the personal goals for older adults (i.e., their present-oriented, relationship-related goals; Carstensen, 1993, Carstensen, 1995), they may trigger other, non-goal-related, concerns about their cognitive abilities and potential intellectual decline (e.g., Hertzog & Hultsch, 2000). Thus, unless subjects are asked about TRI (and they have not been in prior aging studies; Giambra, 1989, Jackson and Balota, 2012; Krawietz et al., in press), we cannot know whether older adults actually experience less off-task thought than do younger adults.
Here, we tested whether apparent age differences in TUTs stem from subjects misclassifying TRI. That is, older adults may experience increased TRI (see Parks, Klinger, & Perlmutter, 1988–89), but may also misclassify TRI as “on-task” thoughts because of forced-choice, on- versus off-task reporting. At least occasionally, subjects may classify performance-evaluative thoughts as “on-task” because they are more task-related than are TUTs about romantic getaways or dinner plans. If older adults experience elevated TRI, due to stereotype threat (Hess et al., 2003, Rahhal et al., 2001) or concerns about cognitive decline (Hertzog & Hultsch, 2000), and if TRI has similar behavioral consequences to TUTs (McVay and Kane, 2009, McVay and Kane, 2012a), then misclassifications of TRI as on-task thoughts should result in older adults appearing more task-focused and less distracted than are younger adults. Moreover, if older adults actually experience fewer TUTs, and yet increased TRI, relative to younger adults, it strains any resource-based explanation of age differences in off-task thought: if older adults' reduced TUT rate is due to deficient resources, then they ought to engage in little TRI-type thinking, as well. Finally, if age differences in TUT reports were largely caused by older adults' inability to assess their subjective experiences (a concern not yet directly tested in the literature), then older adults should show similarly low rates of TUTs and TRI.
Both Jackson and Balota (2012) and Krawietz et al. (in press) reported several findings that underscore the need to distinguish TUT from TRI when assessing age differences. First, in the Jackson–Balota study, older adults showed increased post-error slowing – where response times were longer following incorrect than correct responses – which may reflect TRI (see also Cheyne, Solman, Carriere, & Smilek, 2009). Second, the older subjects tested by Jackson and Balota had higher conscientiousness scores than the younger subjects, indicating a general propensity to care about performing well; they also indicated higher levels of interest in the SART (see also Germain & Hess, 2007), consistent with the older subjects tested by Krawietz et al., who reported greater interest in the reading task than did the younger adults. Such age differences in interest and conscientiousness could lead to more TRI experiences for older than for younger adults in the laboratory. Again, if people frequently misclassify TRI experiences as on-task thoughts, then age-related difference in thought reports might misrepresent the extent to which older adults engage in TUTs.
Section snippets
Experiment 1
In both Experiments 1 and 2 we assessed TRI, a form of off-task thought that may be especially relevant to older adults and may be sometimes misclassified. We also analyzed age differences in the effects of TUTs on performance in several executive-control tasks, as a potential means to distinguish resource-consuming views of mind wandering (Giambra, 1989, Smallwood and Schooler, 2006) from the control failures × concerns view (McVay and Kane, 2010a, McVay and Kane, 2010b). Experiment 1 presents a
Experiment 2
Experiment 2 attempted to replicate the age differences we found in TUTs and TRI during go/no-go and vigilance SARTs, but in an n-back task of working memory (e.g., Gevins et al., 1990, Kirchner, 1958, Mackworth, 1959) that should yield significant age-related deficits in performance. The n-back requires subjects to decide whether each stimulus in a sequence matches the one presented n items ago. n-Back tasks generally show age differences for ns of 2 or higher (e.g., Missonnier et al., 2004,
General discussion
The current experiments expanded upon previous aging and mind-wandering studies. First, we used randomly occurring probes to assess immediately preceding thoughts, rather than predictable probes to assess thought content over 20–30 s periods (cf. Giambra, 1989), as a way to reduce contributions of retrospective-memory deficits in older adults. Second, we probed for an additional category of thought, TRI (cf. Giambra, 1989, Jackson and Balota, 2012; Krawietz et al., in press). TRI reflects self-
Conclusions
Two experiments addressed the possibility that age-related differences in TUTs were due to misclassifications of TRI experiences, and confirmed the finding that older adults mind wander less than do younger adults during ongoing laboratory tasks (Giambra, 1989, Jackson and Balota, 2012; Krawietz et al., in press). We suspect that the age difference in TUTs derives from differential cuing of concern-related, interfering thoughts, and our TRI findings support this, but further research is needed
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