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Maria Lev, Uri Polat; When masking is like crowding. Journal of Vision 2012;12(9):333. doi: https://doi.org/10.1167/12.9.333.
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Visual masking refers to impaired performance on a target stimulus when a mask stimulus is briefly presented before, during, or after the target, at the same, or at flanking locations. Crowding refers to an impaired ability to recognize objects in clutter. Although crowding and masking share very similar features, the underlying mechanisms are not yet understood. We predict that masking and crowding are both affected by the perceptive field (PF) size and are the highest inside the PF and decrease with increasing distance from the PF. To test this prediction, we used our recently developed method for estimating the size of the PF method (Lev & Polat, 2011) and determined whether crowding and masking induced similar effects; subjects with a large suppressive range will have stronger crowding and masking effects. We tested subjects under crowding and masking conditions at both the fovea and periphery. For crowding conditions we used two tasks: letter crowding and alignment task (Gabor patches); flanking masks served as the crowding elements (Bonneh, Sagi & Polat, 2007). For the masking condition we used lateral masking (spatial masking) and lateral masking followed by temporal masks. We estimated the size of the PF for each subject. We found that crowding was correlated with the masking conditions. Although there is variability among subjects regarding the masking and crowding effects, the variability is correlated within subjects; subjects that exhibit stronger masking exhibit a corresponding stronger crowding effect. The spatial range of the crowding and the masking effects was related to the size of the PF for each subject. Thus, the results suggest that masking and crowding share common mechanisms and both depend on the size of the PF. Hence, a unified low-level model of masking may explain the spatial and temporal masking effect as well as the crowding effect.
Meeting abstract presented at VSS 2012
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