Temporal dynamics of effort discounting: The roles of cognitive load and depression.

Effort discounting, or the devaluation of rewards requiring effort, depends on underlying neural computations of reward valuation and cognitive control. Although much is known about effort discounting, its temporal dynamics-how effort valuation changes when required effort is delayed-remain underexplored. Furthermore, although depression has been linked to altered effort and reward discounting, its role in the temporal dynamics of effort valuation remains unclear. In this study, we conducted three experiments to examine how temporal delays alter effort aversion, with a focus on cognitive load and individual differences in depression. In Experiment 1, we evaluated effort valuation by using the Cognitive Effort Discounting (COG-ED) paradigm together with a backward-typing task and found that effort discounting decreases over time for tasks that require high effort. Experiment 2 replicated this pattern by using a working memory (n-back) task, confirming that effort demand modulates temporal effort discounting for high cognitive loads. Experiment 3 investigated whether depressive traits modulate temporal effort discounting. Nondepressed participants showed strong effects of delay at higher effort levels, with effort discounting decreasing over time. In contrast, depressed participants exhibited reduced sensitivity to delay. Hierarchical drift diffusion modeling (HDDM) revealed that nondepressed individuals flexibly adjusted their decision-making by shifting from positive (high-effort) to negative (low-effort) drift rates as effort increased. In contrast, depressed individuals exhibited consistently negative drift rates across all effort levels, indicating a persistent bias toward effort avoidance. Taken together, these findings highlight how cognitive load influences effort valuation over time and suggest that depression blunts temporal sensitivity in effort-based decisions.