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Ana Torralbo, Diane Beck, Arthur Kramer; Perceptual load-induced selection as a result of neural competition in early visual cortex. Journal of Vision 2007;7(9):173. doi: 10.1167/7.9.173.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptual load has been proposed as a determining factor in the degree to which unattended information is processed. Although manipulations that increase visual processing demands have modulated the processing of unattended items, as predicted by perceptual load theory, a clear definition of perceptual load is still needed. Here we propose that sensory competition at the level of the visual cortex may determine perceptual load. The biased competition model of selective attention proposes that stimuli presented simultaneously in the visual field are not processed independently, but instead interact in a mutually suppressive way that suggests a competition for neural representation. Furthermore, this competition can be biased by either bottom-up (e.g. saliency properties of the stimulus) or top-down (e.g. actively searching for the target according to the current behavioural goals) mechanisms. We propose that these suppressive interactions and the resulting top-down biasing mechanisms needed to resolve the competition, may determine the perceptual load of the task, and thus degree to which the unattended information is filtered. We argue that previous manipulations of perceptual load, which include increasing the number and/or the heterogeneity of a set of stimuli, also increase sensory competition. Furthermore, we test a new manipulation of perceptual load derived from predictions of biased competition theory. Specifically we asked whether a variable known to increase sensory competition—the distance between stimuli—will modulate the flanker effect. We varied the distance between items in the search array, while keeping set size and heterogeneity constant and equating the target-flanker separation in both conditions. We found smaller flanker effects for the high density displays than the low density displays, consistent with the idea that the competition and resulting bias necessary to overcome the competition may determine the degree to which unattended information is processed.
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