Browsing by Subject "Psychophysics"

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Open Access
Beyond Bouma's window: how to explain global aspects of crowding?
(Public Library of Science, 2019-05) Doerig, A.; Bornet, A.; Rosenholtz, R.; Francis, G.; Clarke, Aaron M.; Herzog, M. H.
In crowding, perception of an object deteriorates in the presence of nearby elements. Although crowding is a ubiquitous phenomenon, since elements are rarely seen in isolation, to date there exists no consensus on how to model it. Previous experiments showed that the global configuration of the entire stimulus must be taken into account. These findings rule out simple pooling or substitution models and favor models sensitive to global spatial aspects. In order to investigate how to incorporate global aspects into models, we tested a large number of models with a database of forty stimuli tailored for the global aspects of crowding. Our results show that incorporating grouping like components strongly improves model performance. Author summary Visual crowding highlights interactions between elements in the visual field. For example, an object is more difficult to recognize if it is presented in clutter. Crowding is one of the most fundamental aspects of vision, playing crucial roles in object recognition, reading and visual perception in general, and is therefore an essential tool to understand how the visual system encodes information based on its retinal input. Hence, classic models of crowding have focused only on local interactions between neighboring visual elements. However, abundant experimental evidence argues against local processing, suggesting that the global configuration of visual elements strongly modulates crowding. Here, we tested all available models of crowding that are able to capture global processing across the entire visual field. We tested 12 models including the Texture Tiling Model, a Deep Convolutional Neural Network and the LAMINART neural network with large scale computer simulations. We found that models incorporating a grouping component are best suited to explain the data. Our results suggest that in order to understand vision in general, mid-level, contextual processing is inevitable.
Open Access
The spatial extent of size adaptation effect in peripheral vision
(2019-07) Altan, Ecem
It has been shown that prolonged exposure to a certain object size (i.e. size adaptation) alters the subsequent size perception such that the size of the latter appears more dissimilar to the adapted size (Pooresmaeili, Arrighi, Biagi, & Morrone, 2013). However, how much of the visual space is in uenced by the size adaptation at a certain location remains unanswered. Here, in order to investigate the spatial extent of the adaptation effect, we tested the size adaptation effect at the adapted location and various non-adapted locations. In the first psychophysical experiment, we showed a mid-sized adapter stimulus and tested its in uence on subsequent size perception at 5 locations. Results showed that the size perception at non-adapted locations was in uenced by the adapter, although not as much as the effect at the adapted location. In the second experiment, we tested the size aftereffect at 15 different locations and mapped out the perceived size distortions over the visual field. Lastly, in the third experiment, we tested the effect of size adaptation with ring-shaped stimuli and found a substantially large effect just as in the second experiment. These findings overall suggest that the size adaptation does not only have a local effect but also the size perception in consequence of adaptation is being distorted throughout the visual field.