Understanding the relationship between microsaccades and pupil dilation

Abstract

Existing literature reveals little information about the relationship between microsaccade rate and the average change in pupil size. There is a need to investigate this relationship and how the microsaccade rate may be relevant to cognitive load. In our study, we compared the microsaccade rate to the average change in pupil size during eight experimental conditions. Four of them were considered fixation conditions (subjects look at a fixation cross in each visual scene) and four were free-viewing conditions (subjects are free to move their eyes over the visual scene). We analyzed the change in pupil size and microsaccade rate for the first part of each task and as well as the entire task in all conditions. We discovered a significant correlation between the microsaccade rate and the average change in pupil size during the first part of each task, and comparable characteristics throughout the entire task. Then we measured the data for only one of the experimental conditions in free-viewing that involves a search task to understand comparable characteristics related to cognitive load. We found that there is a correlation between the microsaccade and pupil data. We hope that this finding will help further the understanding of the relative function of microsaccades and use it to support cognitive load response and pupil measurement.