Learning to see the Ebbinghaus illusion in the periphery reveals a top-down stabilization of size perception across the visual field

International audienceOur 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

Sensorimotor adaptation of size perception.

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You can laugh at everything, but not with everyone: What jokes can tell us about group affiliations

International audienceThis paper explores the impact of group affiliation with respect to the on-line processing and appreciation of jokes, using facial electromyography (EMG) activity and offline evaluations as dependent measures. Two experiments were conducted in which group affiliation varied between the participant and each of two independent (recorded confederate) speakers whose described political profiles were distinguished through one word: " Right " versus " Left. " Experiment 1 showed that jokes were more highly evaluated and that associated EMG activity was more intense when it was later determined that the speaker was a member of the listener's ingroup rather than outgroup. In an effort to determine whether these parochial effects can be isolated to ingroup favoritism as opposed to outgroup derogation, Experiment 2 paired a joke-teller described as politically active (either from the right or the left) with one who was described as politically neutral. These more subtle comparisons suggest that the parochial effects observed in our joke understanding paradigm are mediated, at least in part, by the presence of an outgroup member