Scientists from Kyoto University have identified a “motivation brake” in the brain—a neural circuit that interferes with initiating unpleasant or stressful tasks and thereby contributes to procrastination. The findings were published in BBC Science Focus.

In the experiments, researchers trained macaques to perform two types of reward-based tasks. One task involved receiving a reward only, while the other offered the same reward but was paired with an additional unpleasant stimulus—a puff of air to the face. When a task did not involve discomfort, the animals began it without hesitation. However, when an unpleasant experience was expected, the monkeys often refused to perform the task or delayed starting it.

Analysis of brain activity revealed that this avoidance behavior is mediated by a neural circuit connecting the ventral striatum—an area involved in reward evaluation and motivation—and the ventral pallidum. When a situation is perceived as stressful, the ventral striatum sends a signal that effectively “applies the brake,” suppressing readiness to act.

To test the role of this mechanism, the researchers temporarily weakened the connection between these regions using chemogenetics—a technique that allows selective control of neuronal activity. After this intervention, the monkeys became noticeably more willing to perform tasks, even when they involved moderately unpleasant sensations.

According to lead author Kenichi Amemori, the discovery helps explain why humans and animals tend to avoid difficult or unpleasant tasks. At the same time, the researchers stress that interfering with such mechanisms in humans is currently unacceptable.

“Excessive weakening of the motivational brake could lead to risky or dangerous behavior,” Amemori noted.

He added that further research and ethical discussion are necessary before such approaches could be considered in a clinical context.