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Laura Walker, Saeideh Ghahghaei; Saccades alter crowding in the parafovea. Journal of Vision 2014;14(10):213. doi: 10.1167/14.10.213.
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Crowding is typically studied during fixation with covert attention to the target, and demonstrates a radial-tangential anisotropy (Toet & Levi, 1992). During natural vision, eye movements necessarily alter the relative relationship of flankers to targets. Here we examine how saccades impact crowding of parafoveal targets. Four participants reported the orientation of a brief gabor target (100ms) in the upper or lower parafovea while keeping their gaze at a central fixation. In separate blocks, target eccentricity and flanker condition were manipulated (absent, radial, tangential). The crowding factor (CF: ratio of crowded to uncrowded conditions) was determined by adaptively changing the size and target-flanker distance (Petrov & Meleshkevich, 2011). For all participants, CF was greater for radial versus tangential configurations and CF increased with eccentricity. In the second experiment, participants made three, timed saccades between four targets. During fixations on the second and third targets, stimuli analogous to experiment 1 were displayed for 100ms during each "look" in a gaze-contingent manner. Participants were again asked to report the orientation of the gabor. Discrimination was not impacted by eye movements in the unflanked condition. When flankers were present and radial/tangential configurations preserved for each "look", the hallmark anisotropy was preserved. When the eye movement served to rotate the flanker configuration with respect to the target, the two looks were cumulative and the CF fell between the radial and tangentially crowded bounds. Notably, the addition of saccades altered the CF as a function of eccentricity. Rather than a monotonically increasing function, the CF increased for targets near the fovea decreased for targets outside the parafovea. This change may be related to the spatial profile of attention during a sequence of eye movements.
Meeting abstract presented at VSS 2014
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