Pupil Diameter and Performance in a Supervisory Control Task: A Measure of Effort or Individual Differences?

The relationship between increased pupil diameter and effort has been well established within the Psychology literature since the 1960s. The ability to detect an individuals’ effort is important, particularly in tasks where there are extended periods of monitoring, and limited ways to directly measure performance. The current study sought to investigate whether pupil diameter could be used to detect periods of high and low workload during an unmanned vehicle supervisory control task. Participants were Navy and Marine Corps student pilots, and the experimenters had access to their aviation selection test scores. The study found increased pupil diameters when the task load increased. In addition, pupil diameter during the high task load condition was significantly correlated with the individual’s performance on the supervisory control task. This paper discusses two possible explanations for this finding: 1) that those individuals who performed better on the task were trying harder or, 2) that pupil diameter was capturing differences in general fluid intelligence which influenced task performance. Previous research has shown that differences in an individual’s working memory capacity are correlated with pupil diameter at rest. Further the significant correlation between pupil diameter and the pilot’s selection test scores in this study provide additional evidence that pupil diameter may be capturing individual differences.