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Matteo Valsecchi, Jan Koenderink, Andrea van Doorn, Karl Gegenfurtner; Appearance of complex stimuli in the peripheral visual field. Journal of Vision 2018;18(10):849. doi: 10.1167/18.10.849.
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Measuring the appearance of peripheral stimuli is a challenging task, given that the drawing and verbal abilities of naïve observers limit the extent to which they can characterize it. We used the eidolon factory (Koenderink et al., JOV 2017), an image-manipulation algorithm based on a formal description of the visual field, in order to provide our observers with a meaningful perceptual space where peripheral appearance can easily be matched. In particular we concentrated on the space defined by the reach and coherence parameters of the eidolon factory, which control the amount of distortion and the degree to which the distortion is applied in a coherent way across scales. Different configurations of the parameters can produce stimuli which are distorted but sharp or distorted and fuzzy. We had 12 observers reproduce in foveal viewing the appearance of images viewed peripherally (20° or 30°) by adjusting the coherence, reach or the combination of both in different trials. The peripheral images were depictions of ensembles of geometric shapes that were perturbed with the eidolon factory (.5 coherence and an arbitrary reach). Observers showed a significant tendency to adjust the centrally viewed stimuli with higher coherence and lower reach when the peripheral stimulus was viewed at 20° and 30°, that is, they reported a regularized appearance. These biases were absent in a control condition where observers looked directly at both stimuli. Our results confirm and extend the phenomenon of sharpness overconstancy in peripheral vision, showing that the fact that we have positional uncertainty and reduced sensitivity for higher spatial frequencies in peripheral viewing by no means lets our peripheral visual field appear distorted and blurred. On the contrary, as the sensory evidence for the contrary is reduced, our visual system generates the impression of a world where boundaries are straight and sharp.
Meeting abstract presented at VSS 2018
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