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Jason S. McCarley, Jeffery R. W. Mounts, Matthew Hillimire; Spatially-mediated attentional interference degrades shape processing. Journal of Vision 2005;5(8):1010. doi: 10.1167/5.8.1010.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Localized attentional interference (LAI) occurs when selection of one item within the visual field degrades processing of nearby stimuli (e.g., Mounts, 2004; McCarley, Mounts, & Kramer, 2004). Competitive network accounts of attention explain this as the product of competition for control of extrastriate neural responses, whereby the selected object alone drives activity across an assembly of neurons. Under this conceptualization, the effect of LAI should be to degrade the observer's ability to organize stimulus properties into structured object representations. The current study tested this prediction by examining the effects of LAI on processing of emergent structural properties (Prinzmetal, 1989). Method: Subjects made speeded same-different judgments of colored target pairs embedded within arrays of gray distractors. Control stimuli were carets comprising a vertical line segment attached to a left- or right-oblique segment. Experimental stimuli were identical to control stimuli, except that a redundant horizontal segment was added to each item to produce either an arrow or a triangle. Spatial separation between attended items varied. Hypothesis was that localized interference between attended items would be greater for stimuli distinguished by structural differences than for control stimuli. Results and conclusions: Data showed substantial LAI for stimuli distinguished by emergent structural features, while control stimuli showed no LAI. A series of additional experiments revealed LAI for stimuli distinguished by shape but not those distinguished by orientation. Results indicate that spatially-mediated interference degrades processing of shape information, and suggest that such interference may emerge only when stimuli are distinguished by features that can be processed in parallel. Findings suggest spatial limits on the ability to form object representations in parallel.
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