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Ricardo Max, Yehoshua Tsal; Selection in Flanker Tasks is Governed by Identities and Not by Locations. Journal of Vision 2015;15(12):1069. doi: 10.1167/15.12.1069.
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© ARVO (1962-2015); The Authors (2016-present)
Distractor processing in flanker tasks has been widely attributed to inherent flaws of the attentional apparatus. We challenge three central premises behind this claim: (a) Early perceptual processing capacity is critically limited and lacks resolution for fully identifying stimuli. Therefore, (b) in order to attain target selection, the system deploys processing resources according to stimuli locations; the relevant (central) location is continually processed, whereas irrelevant (flanking) locations become suppressed. (c) Distractors are processed because attentional mechanisms fail to constrain processing exclusively within the target’s location. The mutations paradigm provides behavioral measurements of the specific time window during which distractors must appear in order to delay responses. A central target is flanked by two identical distractors. In each trial, while the target remains unchanged, both distractors mutate once, either from incongruent to neutral, vice versa, or from neutral to neutral (control). Mutation time is random within the initial 200 ms after onset. Results from six experiments consistently showed: (a) Distractors’ identities were processed as early as 8 ms after onset, which indicates that early perceptual capacity is not limited as believed. (b) Flanking distractors became robustly suppressed as early as 25 ms, indicating a sharp focus of the attentional window exclusively upon the target. (c) When neutral distractors were presented during the initial 30 ms, distractors’ locations became swiftly and irrevocably suppressed. Yet, when a distractor was incongruent within the initial 30 ms, its location continued to be processed and its identity increasingly delayed responses for as long as presented. This indicates not only that identities were recognized before locations were discerned, but also that distractors were suppressed according to their initial identity (and not according to their locations). We propose that the flanker effect is strongly mediated by identity-based selection rather than solely caused by inefficient selection of target location.
Meeting abstract presented at VSS 2015
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