Pupil dynamics reveal preparatory processes in the generation of pro-saccades and anti-saccades in open skill sports athletes

This study investigated pupil dynamics to establish a physiological index of mental processes associated with executive functioning, enabling objective evaluation of cognitive load during training to improve understanding of cognitive control in sport-specific contexts. Using video based eye-tracking, we examined pupil and saccade responses in athletes (N = 40) and non athletes (N = 40) performing an interleaved prosaccade and anti-saccade task. In this task, participants were instructed prior to target appearance to either make a reflexive saccade toward the target (pro-saccade) or inhibit that response and generate a voluntary saccade in the opposite direction (anti-saccade). Larger pupil dilation prior to target onset was observed during anti-saccade compared to pro-saccade preparation (p < 0.001, ηp² = 0.153). Athletes showed reduced pupil dilation compared to non-athletes (p < 0.05, ηp² = 0.049). In addition, trials with larger pupil dilation and smaller tonic pupil sizes were associated with faster saccade reaction times. Pupil dilation also positively correlated with saccade peak velocities but showed no association with saccade endpoint accuracy. These findings suggest that athletes may engage in more efficient motor preparation, as reflected by reduced pupil dilation. Moreover, phasic pupil dilation, indexing cognitive load, and tonic pupil size, associated with arousal level, both contributed to the control of saccade dynamics during goal-directed movements. Together, these results highlight the utility of pupil size as an objective and informative index for assessing both cognitive and arousal functions in sports science research.