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Ed Awh, Miranda Scolari, Jun Ishikawa; Object-based biased competition during covert spatial orienting. Journal of Vision 2008;8(6):224. doi: 10.1167/8.6.224.
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© ARVO (1962-2015); The Authors (2016-present)
Biased competition models assert that spatial attention facilitates perception by biasing the competition for resources between relevant and irrelevant aspects of the visual scene. This emphasis on competition predicts that the benefits of attention will be strongest in high interference displays, when there is significant competition to bias. In line with this view, psychophysical studies have shown larger benefits of covert spatial orienting when multiple distractors impede target processing. Thus, spatial attention resolves visual interference. The present work examined the boundary conditions of this interference resolution process. First, we replicated previous observations of larger spatial cueing effects when observers discriminated target digits that were embedded within distractor letters (noise displays) rather than alone in the visual field (clean displays). However, when the distractor letters were replaced by an equally challenging diffuse noise mask, spatial cueing effects were equivalent in the noise and clean displays. Because the letters and the diffuse noise mask generated equal levels of interference, these data suggest that attention is helpful in resolving a specific kind of competition between individuated object representations. To further test this hypothesis, we measured spatial cueing effects at larger eccentricities where targets and distractors representations are “pooled” because of amplified visual crowding. When crowding made targets and distractors less likely to be perceived as individuated objects, spatial cueing effects were again equivalent in noisy and clean displays. Finally, an analysis of individual differences in susceptibility to crowding showed that the same observers who exhibit weaker crowding effects - and who are more likely to perceive targets and distractors as individuated objects — are the subjects who show larger spatial cueing effects in crowded versus uncrowded displays. These data suggest that spatial attention does not relieve interference from all forms of visual interference. Instead spatial attention biases competition between individuated object representations.
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