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Tingting Liu, Peng Zhang, Yi Jiang, Sheng He; Modulation of the spatial extent of the crowding effect by shaping visual attention. Journal of Vision 2009;9(8):987. doi: 10.1167/9.8.987.
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The visual crowding effect is a ubiquitous phenomenon in peripheral vision. However, the role of spatial attention on crowding remains controversial. Here we examined this issue by manipulating the spatial distribution of visual attention through a pre-cueing paradigm and measuring the strength as well as the critical spacing of the crowding effect. In an orientation discrimination task, a Gabor target was presented in the lower right visual field, and distractors (also Gabor patches) were presented either vertically (above and below the target) or horizontally (left and right of the target), with the distance between the target and distractors varied across trials and serving as one of the independent variables. Just before the appearance of the target and distractor stimuli, observers were asked to perform a Vernier discrimination task or a color discrimination task either in a vertical or horizontal orientation, with the purpose of shaping observers' spatial attention to be along or perpendicular to the axis of the subsequent target-distractor configuration. Results consistently showed a reduced crowding effect as well as a reduction in critical spacing of crowding when observers' spatial attention was pre-cued to be orthogonal to the target-distractor configuration, compared with when attention was pre-cued along the target-distractor configuration. These results provide strong support that both crowding strength and critical spacing of crowding can be modulated by shaping spatial attention and spatial attention plays a critical role in the crowding effect.
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