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Jennifer Anderson, E. Leslie Cameron, J. Jason McAnany, Michael Levine; Crowding and Visual Field Inhomogenieties. Journal of Vision 2014;14(10):771. doi: 10.1167/14.10.771.
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© ARVO (1962-2015); The Authors (2016-present)
For many visual tasks, performance across the visual field is asymmetric typically best along the horizontal meridian (HM) and worst directly above fixation (North). However, this phenomenon has not been examined within a crowding paradigm. Our purpose was to investigate visual field asymmetries in a crowding task by determining how crowder configuration affects threshold throughout the visual field. Crowding thresholds were measured across eight isoeccentric visual field locations in a target discrimination task: Experiment 1 measured crowding threshold for a target within a symmetric ring of crowders, Experiment 2 tested various subsets of this ring. We were interested in how well targets could resist crowding, thus results are reported in terms of "robustness", the inverse of the crowding threshold (1/crowding threshold). Visual field data were fit with ellipses. In Experiment 1, robustness was strongest along the HM and weakest at North and the presence of visual field asymmetries was confirmed. In Experiment 2, the largest differences in visual field robustness patterns were observed when crowders were "between" or "outside" the target and fixation. When "outside" (i.e., crowders at greater eccentricity than the target), visual field patterns indicated high levels of robustness along the HM and robustness data were well fit by a somewhat flattened ellipse. When "between" (i.e., crowders located between fixation and target), the mean robustness of the HM was equivalent to that of the vertical meridian (VM). However, robustness was weak at North and strong at South, presenting an effective "shift" along the VM. These data demonstrate that visual field asymmetries exist even in the context of crowding stimuli. However the specific asymmetric pattern depends upon the configuration of the crowders relative to both the target and fixation. In particular, processing along the vertical meridian is unique, and crowder configuration can either inhibit or enhance robustness.
Meeting abstract presented at VSS 2014
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