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Ahmad Yoonessi, Curtis Baker; Gaze behavior during motion parallax.. Journal of Vision 2012;12(9):1008. doi: https://doi.org/10.1167/12.9.1008.
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© ARVO (1962-2015); The Authors (2016-present)
Motion parallax, or differential image motion resulting from movement of the observer, provides powerful cues for both segmentation and depth perception. During such observer movement, reflexive eye movements occur to counter the foveal image motion. We previously (JOV 2011) measured depth and segmentation performance from motion parallax while minimizing eye movements by keeping a defined fixation point. Here we examine the pattern and influence of eye movements during motion parallax, under different fixation conditions. Observers performed lateral head translation while an electromagnetic tracker recorded head position. Stimuli consisted of random dots, whose horizontal displacements were synchronized proportionately to head movement by a scale factor (syncing gain), and were modulated to generate motion. Eye movements were recorded using a remote optical eye-tracking system. First we measured the ability of observers to maintain fixation during depth and segmentation tasks, using a defined fixation point. The fixational behavior was highly imperfect, with eye position varying around the target fixation point in synchrony with head movement. Thus the reflexive eye movements only compensate for a fraction of the retinal slip due to head movement. With free fixation, segmentation performance was largely unaffected, but depth perception deteriorated at high syncing gains. The fixation pattern again exhibited imperfect cancellation of retinal slip, with variation in synchrony with the head movement. Furthermore during the depth task, observers primarily fixated on the virtual surfaces, whereas during the segmentation task fixation was mostly at their boundary. The amplitude of eye movements was independent of the actual stimulus motion. Thus reflexive eye movements during motion parallax are imperfect, but psychophysical performance is affected only in specific conditions. These results illustrate how gaze behavior can be task-dependent, and suggest that during natural motion parallax observers fixate on surfaces for depth information, whereas they fixate along boundaries for segmentation.
Meeting abstract presented at VSS 2012
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