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Elizabeth Rislove, Dennis Levi; Crowding and feature conjunction in human amblyopia. Journal of Vision 2008;8(6):434. https://doi.org/10.1167/8.6.434.
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Crowding is a phenomenon generally characterized by decreased ability to identify a target among non-overlapping distractors in the normal periphery and central visual field of observers with amblyopia (a condition of degraded spatial vision generally caused by early monocular form deprivation). Several recent studies have related crowding to the feature integration stage of visual processing. Additionally, it has been reported that spatial extent and boundaries of an “attentional spotlight” may have a profound effect on the way in which features are integrated. In order to study feature conjunction in crowding, we chose stimuli that had at least two easily identifiable features (orientation and color). We tested normal and amblyopic observers using a paradigm in which observers were asked to identify the central stimulus among an array of distractors under one of three conditions: (1) no cue, (2) the target was cued with a spatial cue and (3) either the target or one of the distractors was cued using a spatial cue in the same manner as in condition (2). Our stimuli consisted of vertically and horizontally oriented black and white bars as well as possible conjunctions of two bars (one horizontal and one vertical) presented on an otherwise homogeneous gray field. We found that for an observer with a history of abnormal visual experience, cuing the target location (but not distractor locations) improved performance in her affected eye but not her fellow eye. Random location cuing reduced performance in both eyes relative to cuing the target location only. Analysis of incorrect responses revealed that observers are most likely to confuse targets that are combinations of one black bar and one white bar.
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