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Abstract

During translations along the antero-posterior axis, the angular velocity of the visual flow on the retina varies with the retinal eccentricity of the stimulus. We tested how the perceived translation speed is affected by the portion of the retina that is stimulated. Twelve seated subjects were presented with visual translations at constant speed through a volume of random dots. The perceived speed was compared between different field-of-view (FOV) conditions, masks of different sizes being used to occlude either central or peripheral areas of the FOV (230*125 degrees when non-occluded). With central FOVs smaller than 40 degrees (ie, peripheral vision occluded), the visual speed was systematically underestimated, the bias being inversely proportional to the size of the FOV. In contrast, when the central region was occluded and visual flow only presented peripherally, the speed was systematically overestimated. This overestimation was observed even when only 10 degrees of central FOV were occluded. Our results suggest that correct perception of visual speed requires at least 40 degrees of central FOV.