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Lynda Bilodeau, Patrick Cavanagh; Disintegration of shapes in peripherally viewed rotating displays. Journal of Vision 2001;1(3):21. doi: https://doi.org/10.1167/1.3.21.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the perception of shape and motion in the periphery. Methods: Static displays presented outline drawings of squares and circles or static arrays of 4 dots. Observers adjusted the horizontal to vertical ratios until the shapes appeared to be true squares or circles. In the moving displays, 1 to 5 dots traced an elliptical path at 1 rps. Observers adjusted the horizontal/vertical ratio of the elliptical path to make it appear circular. For static and moving displays, settings were made at the fovea and at 3 eccentricities along each of the 4 meridians. Stimulus size was scaled linearly with eccentricity. Results: With one exception, settings for static outline circles and squares were veridical throughout the visual field (H/V ratio = 1). Small deviations were obtained with four outline squares at 40 deg. In contrast, dotted shapes, whether moving or static, showed dramatic distortions in the periphery such that H/V ratios approached 0.5 (vertical ellipse) on vertical meridians and 1.5 (horizontal ellipse) on horizontal meridians. Moreover, observers reported a striking disintegration of the rotating shapes and trajectories as well as frequent loss of one or more of the moving dots. Discussion: Static forms are accurately perceived throughout the visual field. However, the integration of shapes over a set of static dots or motion trajectories suffers severe distortions in the periphery. The accuracy of judgment for explicit outline shapes suggests that the problems for shape integration cannot be traced to distortions of receptive field organization in the periphery as this would affect both stimulus types equally. We conclude that peripheral distortions arise from deficiencies in the spatial integration of incomplete shapes in the periphery.
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