Apathy in Older Adults is Associated with a Selective Over-Weighting of Effort in Everyday Decisions

Apathy, characterized by reduced motivation and goal-directed behavior, is common in normal aging and may arise from biases cost-benefit evaluation during decision making. While prior research has focused on simple choices involving the trade-off between motor or cognitive effort and monetary reward, real-life decisions of people with apathy likely reflect biases affecting many other dimensions of value. Additionally, the extent to which mood symptoms that frequently co-occur with apathy also contribute to biases in decision making is unclear. To address these gaps, we developed a novel online task completed by 158 older adults who rated everyday activities (e.g., watching TV, going to the park) across 19 value attributes (e.g., enjoyment, social obligation), and made a series of choices between different activities. A factor analysis of attribute ratings identified three latent factors representing reward, effort, and obligation, which strongly predicted choices and choice response times. Apathy was selectively associated with an overweighting of effort-related attributes while controlling for impulsivity and depression, with no effect on the weighting of reward or obligation. Interestingly, impulsivity, which correlated positively with apathy, was associated with an underweighting of effort. Hierarchical drift diffusion modelling supported these findings: apathy and impulsivity modulated the influence of effort on drift rate in opposite directions, altering evidence accumulation toward or away from high-effort options. Overall, these results suggest that everyday decisions depend on the integration of a wide range of value attributes and that apathy is associated with a selective overweighting of the perceived cost of effort.