Goal-directed choices about health, finance, and general well-being are more vulnerable to inferior outcomes at later stages of life. This is an urgent and widespread societal problem especially because human life expectancy is increasing. It is thus important to find out how we can support older adults when making goal-directed decisions. One promising research direction aims to try to understand how and why the neurocomputational mechanisms of goal-directed decision-making change the way they do over the lifespan. Such research may be able to discover how and why the process of ageing results in changes to these mechanisms underlying complex goal-directed decision-making performance.
The research carried out in this project aimed to contribute insights related to the effects of the complexity of the choice environment to this research direction. Together, the overall objectives aimed to identify age-related changes in the neuro-computational mechanisms underlying goal-directed decision making by using experimental and modeling approaches. The ultimate goal was to help identifying insights that can be used to support older adults in their daily decision-making, thus contributing to their general well-being. The project had three overall objectives. The first objective aimed to establish variability in decision strategies between younger and older adults across a range of different choice environments. The second objective aimed to explain such variability mechanistically. As such, the second objective aimed to assess the effects of increasing cognitive limitations across the lifespan by identifying and comparing the cognitive demands of the strategies that younger and older adults are adopting across task demands. The third objective was similar to the first objective but aimed to establish variability in decision strategies across the entire lifespan instead.
Most of the work was focused on studying how older adults behave in the explore-exploit dilemma. The explore exploit dilemma is ubiquitous in daily life because there are often too many options available to explore exhaustively. The n-armed bandit task is a well-known task that is excellently suited for studying this question. We studied how older and younger adults solved four and eight option bandit problems and how performance relates to structural connectivity in cortico-striatal loops and performance on a number of psychometric tests. We found that older adults reliably chose the most rewarding options less often than younger adults, especially in more complex choice environments. The decline in decision-making performance over time is large for more complex choice environments and medium in less complex choice environments. Older adults needed more exploration than younger adults to be able to distinguish between options. Furthermore, causal inference showed performance was connected to a simple math test directly. However, age group was more strongly associated with cortico-striatal connectivity strength, fluid intelligence, working memory, IQ, and risk taking as compared to performance itself. Together, older adults seem to process uncertainty that is associated with options in more complex choice environments sub-optimally, suggesting more limited task representations or inadequate future reward representations. The stronger the demands of the choice environment, the larger the age-difference, indicating limited available cognitive resources in older adults. This result fits to multiple contexts in the complex cognitive aging literature, and in particular to the context of challenges in the maintenance of goal-directed learning mechanisms.
