Abstract
Our conscious visual perception relies on predictive signals, notably in the periphery where sensory uncertainty is high. We investigated how such signals could support perceptual stability of objects’ size across the visual field. When attended carefully, the same object appears slightly smaller in the periphery compared to the fovea. Could this perceptual difference be encoded as a strong prior to predict the peripheral perceived size relative to the fovea? Recent studies emphasized the role of foveal information in defining peripheral size percepts. However, they could not disentangle bottom-up from top-down mechanisms. Here, we revealed a pure top-down contribution to the perceptual size difference between periphery and fovea. First, we discovered a novel Ebbinghaus illusion effect, inducing a typical reduction of foveal perceived size, but a reversed increase effect in the periphery. The resulting illusory size percept was similar at both locations, deviating from the classic perceptual difference. Then through an updating process of successive peripheral-foveal viewing, the unusual peripheral perceived size decreased. The classic perceptual eccentricity difference was restored and the peripheral illusion effect changed into a fovea-like reduction. Therefore, we report the existence of a prior that actively shapes peripheral size perception and stabilizes it relative to the fovea.
Highlights
Our conscious visual perception relies on predictive signals, notably in the periphery where sensory uncertainty is high
We focused on object size, which appears slightly smaller in the periphery compared to the fovea[8,9,10]. What can such size underestimation tell us about predictive mechanisms subtending peripheral perception? In addition to coping with the heterogeneity of sensory input, how do predictive mechanisms support perceptual stability across the visual field? We tested the existence of a top-down contribution to the perceptual size difference between periphery and fovea
In this experiment we showed that the Ebbinghaus illusion can be used to bias the classic perceptual size difference between periphery and fovea
Summary
Our conscious visual perception relies on predictive signals, notably in the periphery where sensory uncertainty is high. The same object appears slightly smaller in the periphery compared to the fovea Could this perceptual difference be encoded as a strong prior to predict the peripheral perceived size relative to the fovea? We focused on object size, which appears slightly smaller in the periphery compared to the fovea[8,9,10] What can such size underestimation tell us about predictive mechanisms subtending peripheral perception? We tested the existence of a top-down contribution to the perceptual size difference between periphery and fovea Such a mechanism would support a stable perception of size across the visual field, which is crucial to guide efficiently our interactions with the surrounding world. We found specific inducers eliciting a reduction of perceived size in the fovea, and a reversed increase effect in the periphery This Ebbinghaus disk deviated from the classic perceptual. We hypothesized that if the difference in perceived size between periphery and fovea is a key aspect of perceptual stability, the deviating peripheral percept would be updated to better match this difference
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