Longitudinal Relationships Between Resources, Motivation, and Functioning

Engagement in cognitively complex activities is frequently touted in the popular press as one way of warding off the more negative effects of aging on our memory and thinking. This belief is encouraged by a substantial body of evidence, suggesting that people who engage in complex cognitive and social activities perform better on cognitive ability tests than those who do not and show less longitudinal decline in cognitive ability across time (for review, see Hertzog, Kramer, Wilson, & Lindenberger, 2008). Although the “use it or lose it” hypothesis enjoys both popular and scientific support, the focus has primarily been on the consequences of cognitive engagement on performance. Little of this research, however, is aimed at examining the reasons that older adults may increase or decrease their engagement over time. In other words, faced with the prospects of declining cognitive functioning, why do some older adults engage while others withdraw? One possibility is that declining physical and cognitive capabilities may cause changes in the motivation to engage. For example, the Selection, Optimization, and Compensation model (Baltes, Staudinger, & Lindenberger, 1999) argues for a shift from growth-based to loss-based goals in later life as older adults focus their resources on prevention of loss and maintenance of functioning. A somewhat different but not inconsistent perspective on age-based motivational forces has to do with changes in personal resources—broadly defined—which affect an individual’s willingness to engage the complex cognitive operations necessary to support performance. For example, fatigue, stress, and time pressure could be characterized as limiting resources, and all have been observed to affect younger adults’ motivational levels, which subsequently influenced performance (e.g., LePine, LePine, & Jackson, 2004; Webster, Kruglanski, & Richter, 1996). The aging process may also negatively affect resources. Hess and colleagues (Hess, 2006; Hess & Emery, in press; Hess, Germain, Swaim, & Osowski, 2009) have hypothesized that age-related changes in health and ability result in greater selectivity in task engagement in later life due to changes in both the relative costs of, and the resources necessary to support, performance. This perspective implies that there should be a linkage between resources and motivation, with this linkage in part accounting for age differences in behavior. In support of this relationship, Hess, Germain, Rosenberg, Leclerc, and Hodges (2005) and Hess, Waters, and Bolstad (2000) found a stronger association between cognitive and health-related resources and motivation—Personal Need for Structure (PNS)—in older than in younger and middle-aged adults. They also observed that motivation was a stronger predictor of performance in later life. Similarly, a closer link has been observed between physical symptoms and depression in later life (e.g., Moldin et al., 1993; Murphy, 1982), providing further support for an increasing association between physical resources and affective outcomes. Finally, Hess (2001) found that age differences in ability and health were predictive of motivation, which in turn accounted for variability in self-reported engagement in everyday cognitive and social activities. Other research with older adults has also demonstrated relationships between intrinsic motivation and both cognitive performance and engagement in everyday activities. For example, Parisi, Stine-Morrow, Noh, and Morrow (2009) found that predispositional engagement—as indexed by a composite of measures relating to mindfulness, Need for Cognition (NFC), and openness to experience—was positively associated with several measures of cognitive ability and some facets of activity engagement. Similar results were obtained by Salthouse, Berish, and Miles (2002). These findings further support the potential importance of motivation in understanding age differences in cognitive performance and everyday activity. A limitation of this prior work relates to the cross-sectional nature of the data. For example, models examining mediation using such data have been shown to result in biased estimates of longitudinal relationships (e.g., Maxwell & Cole, 2007). Stronger support for the linkage between resources, motivation, and behavior would come from longitudinal data that charted changes between these factors. This was the goal of the present study. Specifically, we examined how changes in resource-related factors, such as health and ability, were related to changes in motivation and whether these changes in motivation were subsequently associated with changes in participation in cognitively demanding activities. Our motivational factor involved a composite of two related constructs: PNS (Neuberg & Newsom, 1993) and NFC (Cacioppo, Petty, Feinstein, & Jarvis, 1996). Both are related to preferences for demanding versus less complex cognitive activity. PNS has been characterized as a dispositional motive reflecting the need to cognitively structure one’s world (Neuberg & Newsom, 1993). Individuals who are high in PNS display a preference for simple, well-defined structures for understanding the world and engage in cognitive activities oriented toward reducing ambiguity and simplifying representations (e.g., Moskowitz, 1993; Neuberg & Newsom, 1993; Vess, Routledge, Landau, & Arndt, 2009). Relatedly, NFC is characterized as a relatively stable intrinsic motivational factor reflecting the degree of enjoyment associated with engaging in cognitively demanding activities and is associated with engagement in complex thought (for review, see Cacioppo et al., 1996). Both constructs are representative of more than just ability in that they predict engagement in cognitive activity (e.g., Cacioppo et al., 1996). As can be inferred, these variables are negatively correlated, and shared variance should reflect a general preference for engaging in complex versus simple thought. Importantly, these constructs have been previously studied from a differential perspective involving cross-sectional comparisons across individuals. We extend those findings by examining intra-individual changes in these processes as they unfold over time. In our study, we predicted that changes in resources reflected in physical and sensory functioning, mental health, and ability would affect motivation, with, for example, normative age-related declines in physical health being associated with reduced motivation to engage in complex or effortful activities. We also predicted that changes in motivation would predict changes in engagement in cognitively demanding everyday activities (e.g., reading, social interactions). We further investigated whether changing motivation would be associated with changes in performance on tasks commonly used to assess cognitive ability (e.g., working memory). There are two ways that this relationship could be conceptualized. First, ability might be characterized as a resource factor (e.g., Hess, 2001), with, for example, reductions in working memory being associated with decreases in the motivation to engage in complex cognitive activity. It is also conceivable, however, that scores on these ability tests might reflect changing levels of motivation (i.e., performance as opposed to competence). This directional issue is somewhat analogous to that associated with investigations of the causal linkages between cognitive ability and engagement in cognitively stimulating activities (e.g., Hertzog, 2009). The present investigation has the potential not only to contribute to our understanding regarding the directionality of this relationship but also to highlight motivational mechanisms that may underlie this relationship (e.g., reductions in motivation to engage in cognitively complex activities ultimately lead to declines in performance on tests of ability). Thus, we examined whether the strength of effects involving these abilities and motivation were stronger when considered as resources or as outcomes. Finally, we predicted that motivation would at least partially mediate the relationship observed between changes in our resource and outcome factors. Consistent with previous observations of stronger linkages between resources and motivation in later life (e.g., Hess et al., 2000), we also were able to examine the possibility of moderated mediation effects (Muller, Judd, & Yzerbyt, 2005), that is, that the just-described mediation relationships might be accentuated in later life. Figure 1 presents a visual depiction of the relationships under investigation. Figure 1. General model depicting relations between resources, motivation, and engagement in cognitively demanding activities. Age is depicted as being associated with some resource variables as well as potentially moderating their influence on motivation.