Engagement in potentially beneficial activities is assumed to be based partially on perceived costs and benefits. Mental fatigue may be one factor that affects perceived costs. We examined age differences in both chronic and situational mental fatigue, and their relation to task perceptions and engagement levels. Younger (M age ϭ 32.6) and older (M age ϭ 73.1) adults completed questionnaires measuring subjective mental fatigue, physical and mental health, and motivational states, along with several assessments of cognitive ability. In addition, assessments of effort expenditure (systolic blood pressure) and task difficulty were collected during performance of a cognitively demanding memory-scan task. Two components of chronic mental fatigue (CMF) relating to affect and motivation were identified. Although the structure of CMF did not vary with age, CMF was differentially predictive of engagement and appraisal levels across groups. As CMF-Affect levels increased, older adults' task-difficulty appraisals increased more than those of younger adults. In addition, CMF-Affect was positively associated with levels of engagement in the young, but negatively associated in the old as memory load increased. Older adults also exhibited higher levels of situational fatigue than did the young, as evidenced by increased levels of effort expenditure as both time on task and objective demands increased. However, little relationship existed between chronic and situational mental fatigue in either age group. These findings suggest that the affective aspect of CMF is particularly consequential in older adults, with both task appraisals and engagement levels being negatively affected when fatigue is high.

There have been suggestions that the measure of future time perspective shows a two-factor structure. However, the two-factor structure coincides with positively- and negatively-framed items potentially indicating a method factor rather than a content factor. By using reversed-scored items in an adult sample (N = 1421, aged 19 to 79, M = 39.1, SD = 11.1), we found evidence that the two-factor structure is mainly due to the framing of the items representing method factors rather than representing separate content factors. Item framing might be more important in aging-related research than expected.

Research has shown the amount of effort we expend towards our goals depends on a sense of self-efficacy, perception of task difficulty, and likelihood of achieving our goal. All of these processes are susceptible to the influence of affect. For example, negative moods may impede goal achievement by increasing perceptions of difficulty (Silvestrini & Gendolla, 2019). Negative experiences (such as past failures) can encourage these negative moods and subsequently impact self-efficacy (Esposito, Gendolla, & Van der Linden, 2014). Findings from self-efficacy research (e.g. Esposito et al., 2014) suggest that older adults may be particularly susceptible to the impacts of negative affect on effort mobilization, especially when tasks already seem challenging, with little chance of success. Perception of task difficulty, then, impacts the amount of effort exerted in completing the task. The present study sought to examine the factors that impact perceptions of difficulty and subsequent effort expenditure, represented by systolic blood pressure responsivity (SBP-R). Younger (N = 41) and Older (N = 163) adults completed a difficult cognitive task as part of a larger, longitudinal study, as well as measures of trait affect before study sessions. Our findings indicate younger adults exert less effort overall than older adults; however, when negative trait affect is considered, we find that higher levels of negative affect in older adults reduced task engagement. These results provide support for an effect of negative affect on task appraisals and posited age-related differences in effort mobilization.

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