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Mara Lev, Oren Yehezkel, Uri Polat; Temporal processing overcomes spatial crowding in the fovea. Journal of Vision 2013;13(9):574. doi: https://doi.org/10.1167/13.9.574.
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© ARVO (1962-2015); The Authors (2016-present)
It is widely accepted that in the fovea, crowding does not exist or it only occurs over very small distances. Our recent finding that spatial and temporal crowding are correlated, suggesting tradeoff between spatial and temporal processing, led us to hypothesize that limited temporal processing should result in increased crowding. We measured the crowding effect on an E target presented for 30, 60, 90, and 120 ms. The spacing between the target and the surrounding E was one letter spacing. To measure the temporal effect on crowding, we performed another experiment in which a mask was presented after the crowded target (backward masking, BM) using an inter-stimulus interval (ISI) of 30, 40,50, 60, 90, and 120 ms. In both experiments we measured the percentage of correct (PC) and the reaction time (RT). The results show that whereas a small crowding effect is found only with a short duration of 30 ms, RT was significantly slower in all crowded presentations by about 50 ms for all presentation times. Moreover, when BM was used, a significant crowding effect was found for both 30 and 60 presentation times and for all durations and ISIs. The maximal effect of BM was for ISI=30 in which PC was reduced from 93% to 67%. This effect was reduced with increasing ISI values, reaching a reduction in PC from 100% to 85%. Similarly, the RT was significantly slower for all conditions by more than 100 ms. Thus, the results show that absent crowding in the fovea is achieved but by a further processing time (increased RT) that overcomes the spatial crowding. When the processing is interrupted by backward masking, the spatial crowding is revealed. Thus, crowding exists throughout the visual field, but efficient temporal processing in the fovea eliminates the crowding.
Meeting abstract presented at VSS 2013
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