Poster Session: Event-related Changes in Pupil Size in a Simulated Air Refueling Task.

Abstract

There are many factors that influence the behavior of the pupil, but it is functionally an instrument of the visual system; its fundamental role is to balance light and image quality. Though it is common to use pupil size as a measure of other operator-state parameters such as cognitive workload or stress, its role in the visual system can complicate this. It may be more useful to assess dynamic, rapid changes in pupil size in response to workload or stress related events. Here, we measured pupil size velocity in 14 participants who were engaged in an aerial refueling simulation on a 3D display. Refueling collisions (when the fuel nozzle hits the receiver aircraft outside of the refueling receptacle) were recorded, and the pupil velocity at all time-points 10 seconds prior and 10 seconds post-collision were averaged to calculate the event-related change in pupil velocity. On average, there was a -0.49 mm/sec spike in pupil velocity that began 0.39 seconds after the collision and lasted 1.62 seconds before returning to stasis. This suggests that the collision caused a rapid pupil constriction, indicating a stress related change. Approximately 2 seconds post-collision, the pupil began to drift back toward its static state, showing a quick return to its role in promoting good image quality. These data represent a novel way of considering the pupil in the context of its many influences and suggests that rapid spikes in pupil size may indicate an increase in operator stress.