Pupil Dilation Variability as an Indicator of Arousal Regulation: Towards Understanding Operator Functional State

The pupil dilation of fifteen air traffic control students was recorded as they completed the mental counters working memory task. Standard deviation of pupil dilation for each of the 32 trials was computed for each individual and modeled as a growth curve. Pupil dilation variability fluctuated over time in a nonmonotonic manner. Interestingly, the magnitude and direction of pupil dilation variability differed across individuals, suggesting individual differences in arousal regulation. Performance measures of mental counters (i.e., accuracy and response time) were added as predictors to the growth curve model. Higher accuracy was associated with lower pupil dilation variability in general, suggesting better arousal regulation. Longer response times were associated with a greater fluctuation in pupil dilation variability, suggesting longer responses are associated with larger dysregulation of arousal. These findings are important to consider when developing real-time indicators of an operator’s functional state.