Behavioral strategies and pupillary response in a rewarded stop-signal task

Cognitive control, specifically inhibition, is essential for behavior adaptation to environmental changes. While reward expectation influences cognitive strategies, it is still underexplored how reward may influence inhibitory control and how and whether this may be reflected in autonomic physiological responses. In this study, we explore whether trial-by-trial reward cues modulate both behavioral performance and pupil size, an autonomic correlate of cognitive effort. Twenty-five participants performed a rewarded Stop-Signal Task under three reward conditions: Go Plus (greater reward for correctly performed movements Go trials), Stop Plus (greater reward for correctly inhibited movements Stop trials), and Neutral (equal reward for both trial types). Although inhibitory ability remained unchanged across reward conditions, Go trials' accuracy was higher in Go Plus and Neutral conditions. Reaction times were longer in Go trials in the Stop Plus condition, where inhibition was most rewarded. When task strategies required balancing focus to achieve high rewards in both trial types, pupil size increased, suggesting increased cognitive effort. These findings support the hypothesis that reward expectancy shapes cognitive control and its autonomic correlates.