Monkeys adjust goals and strategies in a foraging task based on time constraints

Humans and animals often operate under varying time constraints that demand not only changes in action speed but also adjustments in how many tasks they pursue. These adjustments require fundamental reconstructions of goals and strategies. Additionally, finding a good "compromise" by reconciling goals with feasibility poses a complex optimization problem that involves selecting an effective combination of tasks. Time constraints are ubiquitous across ecological contexts, yet little is known about what behavioral and neural bases support these flexible adaptations. To address this, we devised a behavioral paradigm in macaques, wherein they foraged for as many reward items as possible under various time constraints. The reward map (randomized reward sizes and spatial distributions) and the time limits were visually presented before the start of foraging. We found that the monkeys selected an effective route that maximized the total gain while avoiding time overruns by flexibly adjusting their action speed, the number of rewards to collect (goals), and which ones to prioritize (strategies). Specifically, under shorter time limits, they prioritized larger or more proximal rewards, enhancing time efficiency while accepting opportunity loss by skipping smaller or distant rewards. To further investigate the neural basis of these behavioral adjustments, we systemically manipulated dopamine, which plays a key role in both action and reward processing. Blockades of dopamine D1R prolonged action initiation, while blockades of D2R caused excessive acceptance of opportunity loss in a time limit-dependent manner. These results suggest that dopamine coordinates rapid action and reward compromise, supporting adaptive decision-making under time constraints.