The impact of age and motivation on cognitive effort: implications for cognitive engagement in older adulthood.

We examined age differences in the effort required to perform the basic cognitive operations needed to achieve a specified objective outcome, and how hypothesized increases in effort requirements in later life are related to intrinsic motivation associated with enjoyment of and participation in effortful cognitive activities. Young (N = 59; 20-40 years) and older (N = 57; 64-85 years) adults performed a memory-search task varying in difficulty across trials, with systolic blood pressure responsivity-calculated as the increase over baseline during task performance-used as a measure of effort expenditure and task engagement. Consistent with expectations, older adults exhibited greater levels of responsivity (i.e., effort) at all levels of objective task difficulty, and this increase was reflected in subjective perceptions of difficulty. Older adults also exhibited greater levels of disengagement (i.e., effort withdrawal) than younger adults at higher levels of task difficulty, conceivably reflecting the disproportionately greater effort required for successful performance in the former group. We also found that, relative to younger adults, older adults' engagement was more sensitive to the importance attached to the task (i.e., motivation to do well). Finally, we also obtained evidence that increased costs associated with cognitive engagement in later life were negatively associated with intrinsic levels of motivation to engage in effortful cognitive activity. The results support the general conclusion that the costs of cognitive activity increase with age in adulthood, and that these costs influence individuals' willingness to engage resources in support of demanding cognitive activities.