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Katharina M. Zeiner, Manuel Spitschan, Keith A. May, Li Zhaoping, Julie M. Harris; Eye movements and reaction times for detecting monocular regions in binocularly viewed scenes. Journal of Vision 2011;11(11):326. doi: https://doi.org/10.1167/11.11.326.
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© ARVO (1962-2015); The Authors (2016-present)
Our binocular view of the world is scattered with monocular regions, that only one eye can view. These occur at each depth edge. In previous research, we found that monocular target items are detected faster than binocular targets in a stimulus filled with binocular distractors. Here we explore whether monocular targets also direct eye movements whilst observers perform a visual search task.
Participants performed a classic search task to detect a target C amidst 254 distractor O's, in one of 3 conditions: 1) monocular target, all distractors binocular, 2) one monocular distractor, all other distractors and target binocular, 3) target and distractors binocular. Stimuli were presented using a modified Wheatstone Stereoscope. Reaction times for target detection were measured and eye movements were recorded using an infrared eye tracker. Stimulus onset was contingent upon central fixation. The target was always located towards the left or right side of the stimulus. We measured whether the first saccade was towards the half of the stimulus that contained the target.
On average, reaction time followed the pattern previously observed: if the target was monocular, reaction times were shortest, while if there was one monocular distractor, and the target was binocular, reaction times were longest. In condition 2 we found that the slower reaction times were mirrored by lower rates of correct eye movements. In condition 1 we observed that individuals giving faster reaction times showed a higher number of correct saccades, while those with slower reaction times tended to show fewer correct saccades.
Our results suggest that moving the eyes rapidly towards a monocular region may aid its fast detection. This could help in the identification of object edges, and in the perception of depth from binocular disparity.
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