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Eye Tracking, Pupillometry, and Visual Attention

Pupillometry measures small changes in pupil size but what do these changes mean? Our lab suggests that these changes in pupil size may reflect differences in the attentional spotlight. When you focus on something small that is hard to read, you squint in order to minimize light coming into the retina in order to help resolve the image. When you go from a dark environment to a light environment, your eyes constrict in order to control the amount of light falling on the retina and help you regain focus. Pupil response is also impacted by changes in the focus of attention. For example, when we want to focus on small or local parts of a scene, do we constrict the pupil, even in the absence of lighting differences?

Our lab answers these questions by measuring pupil changes using an eye tracker while participants report local or global elements of Navon figures (larger letters made up of smaller letters). Our current results suggest that the selection of local information (i.e. small details) is associated with a greater pupil constriction relative to selection of global information (i.e. larger, gestalt features). Furthermore, individual differences in pupil response during global-local processing is associated with broader autism traits, suggesting a role for this selection bias in the tendency of individuals with autism to ‘miss the forest for the trees’. We utilize a novel analytic approach that characterizes pupil response as a physiologic signal (much like electroencephalography or functional imaging) and maintains temporally rich data in order to characterize pupil trajectories in response to certain stimuli or in the context of a certain task. Our research focuses on quantifying variability in pupil response trajectories and linking pupil response profiles with visual attention abilities and core clinical symptoms neurodevelopmental disorders such as autism.

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