Perceptual rivalry and the relationship between microsaccades and pupil dilation
63.439, Wednesday, May 15, 8:30 am - 12:30 pm, Orchid Ballroom
Brian Metzger1,2, Diane Beck1,2, Daniel J. Simons1,2; 1Department of Psychology, University of Illinois Urbana-Champaign, 2Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign
Microsaccade rate and changes in pupil size each have been linked to attention (Rolfs, 2009; Gabay et al., 2011) as well as to perceptual alternations in binocular rivalry (Van Dam & Van Ee; Einhaeuser et al., 2008), suggesting a relationship between microsaccade inhibition and pupil dilation. The two measures have been studied independently, though, so it remains unclear if these changes are related. Experiment 1 explored the relationship between the two measures. Microsaccade rate and pupil size were recorded using a video-based eye-tracker as participants viewed orientation-ambiguous figures such as a Necker cube. Increases in pupil size were accompanied by decreases in microsaccade rate while decreases in pupil size were accompanied by increases in microsaccade rate during transitions from one interpretation to the other, confirming that the measures are associated. This covariation either indexes a shared cognitive component such as effort (Valsecchi & Turatto, 2009; Norman & Bobrow, 1975) or a more general association such as an automatic physiological link. To determine whether they co-vary due to a physiological link, Experiment 2 manipulated pupil size by modulating screen luminance and measured changes in microsaccade rates. Although pupil size changed with increases and decreases in luminance, microsaccade rates were not associated with those changes. Consequently, the association between pupillary responses and microsaccades seems to require a shared cognitive component such as attention or cognitive effort.