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Adeola Harewood, Francesca Fortenbaugh, Lynn Robertson, Michael Silver; Visual field shape influences critical spacing in visual crowding. Journal of Vision 2016;16(12):235. doi: 10.1167/16.12.235.
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© 2017 Association for Research in Vision and Ophthalmology.
Behavioral performance is better in the lower than in the upper visual field for a variety of perceptual tasks, including visual crowding. We recently showed that the lower visual field advantage for visual crowding could be accounted for by asymmetry in the shape of the visual field along the vertical meridian. Here, we are continuing this work by studying visual field asymmetries in critical spacing - the minimum distance between a target and its flankers that is needed to enable a certain level of performance on a crowding task. Upper and lower visual field extents were measured in each participant with a Goldmann perimeter. Participants (n=13) then completed a crowding task in which they discriminated the orientation of a target grating in the presence of flanker gratings. The spacing between gratings was altered on each trial using an adaptive staircase to find the 79% performance threshold (i.e., critical spacing). The target grating was always on the vertical meridian, in either the upper or lower visual field. We found smaller critical spacing in the lower visual field than in the upper visual field when stimuli were placed at the same eccentricity in units of degrees of visual angle (p=.03), consistent with a lower visual field advantage. However, when stimulus locations were matched based on percentage of visual field extent instead of in degrees of visual angle, critical spacing for the stimuli in the lower matched condition was similar to that in the upper visual field (p=.80), and critical spacing in the upper matched condition was similar to that in the lower visual field (p=.57). We are currently assessing the effects of spatial attention on critical spacing and examining the relationship between visual field shape and critical spacing for a range of eccentricities.
Meeting abstract presented at VSS 2016
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