Effort cost of harvest affects decisions and movement vigor of marmosets during foraging.

Why do economic variables such as reward and effort affect both the decision-making and the motor-control circuits of the brain? Our results suggest that as the brainstem neuromodulatory circuits that control pupil size respond to effort costs, they alter computations in the brain regions that control decisions, encouraging work and delaying gratification, and the brain regions that control movements, suppressing energy expenditure and reducing vigor. This coordinated response may improve a variable relevant to fitness: the capture rate.