Analysis of microsaccades and pupil dilation reveals a common decisional origin during visual search

• Viewers were asked to search a target embedded in a 1/f abstract image.
• During visual search, viewers often refixate on the same target or image location.
• We analyzed microsaccades and pupil dilation during eye refixations.
• Both the rate of microsaccades and pupil dilation are modulated by detection and decision, revealing a common origin.
• Moreover, microsaccades depend on the visual content of the region being fixated.

During free viewing visual search, observers often refixate the same locations several times before and after target detection is reported with a button press. We analyzed the rate of microsaccades in the sequence of refixations made during visual search and found two important components. One related to the visual content of the region being fixated; fixations on targets generate more microsaccades and more microsaccades are generated for those targets that are more difficult to disambiguate. The other empathizes non-visual decisional processes; fixations containing the button press generate more microsaccades than those made on the same target but without the button press. Pupil dilation during the same refixations reveals a similar modulation. We inferred that generic sympathetic arousal mechanisms are part of the articulated complex of perceptual processes governing fixational eye movements.