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Abstract:
While walking, the visual scene analysis provides both structural information about the environment, and self-motion characteristics. These two categories are in fact strongly interrelated. During constant speed translations on a plane, the angular retinal speed varies according to where we look at, and still self-linear speed is perceived as constant which allows the world to appear stable. We studied factors involved in the retinal-to-linear compensation mechanism underlying this perceptual stability. In all experiments we used a speed discrimination task between two gaze directions (12°, 20°, or 28° below horizon). When keeping the eyes static, the compensation was almost perfect if viewed with a full field 86, whereas it was poorer, but far from null, if viewed with a 6° vertical aperture 74. When tracking a target on the plane, this compensation improved for both full and limited field. Finally, reducing the visual scene to the tracked target also allowed for good compensation, though worst than with the plane. These findings are discussed with regard to inverted structure-from-motion mechanisms.
