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Søren Kyllingsæk, Jocelyn L. Sy, Barry Giesbrecht; Understanding the Allocation of Attention when Faced with Varying Perceptual Load in Partial Report: A Computational Approach. Journal of Vision 2011;11(11):134. doi: https://doi.org/10.1167/11.11.134.
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© ARVO (1962-2015); The Authors (2016-present)
The allocation of visual processing capacity is a key topic in visual attention. Load Theory (LT, Lavie, 1995) proposes that allocation happens in two stages where resources are allocated to task-relevant stimuli in the first stage and any remaining capacity ‘spills over’ to task-irrelevant stimuli in the second stage. In contrast, the Theory of Visual Attention (TVA, Bundesen, 1990) proposes that allocation happens in a single step where capacity is allocated to all stimuli, both task-relevant and task-irrelevant, in proportion to their relative attentional weight. These models have three key differences: 1) LT predicts no effect of similarity between the task-irrelevant distractors and the target, TVA does; 2) LT predicts no effect of the number of task-irrelevant distractors, TVA does; and 3) LT predicts no change in performance when task-irrelevant distractors are absent, TVA does. We tested these divergent predictions in two partial report experiments in which the number and discriminability of task-irrelevant stimuli (Experiment 1) and perceptual load (Experiment 2) were manipulated. The results of Experiment 1 revealed performance decrements when the number of flankers was increased and performance enhancements when the discriminability between the target and the flankers was increased. The results of Experiment 2 replicated and extended the findings of Experiment 1, while also showing nonlinear interaction between the effects of perceptual load and the number of task-irrelevant flankers. Quantitative TVA model fits captured the patterns in the behavioral data, while also showing that that the effects of varying perceptual load can only be explained by a combined effect of allocation of processing capacity as well as limits in visual working memory. Considered together our behavioral and computational modeling results are inconsistent with two-stage allocation scheme proposed by LT, but rather are consistent with the straightforward predictions made by the single stage allocation scheme proposed by TVA.
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