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Shira Tkacz-Domb, Einat Rashal, Yaffa Yeshurun; Spatial and temporal crowding with normal observers. Journal of Vision 2014;14(10):778. doi: 10.1167/14.10.778.
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© ARVO (1962-2015); The Authors (2016-present)
Spatial crowding refers to impaired target identification when it is surrounded by other stimuli in space. Temporal crowding refers to impaired target identification when it is surrounded by other stimuli in time. When temporal and spatial crowding were measured in the fovea they were interrelated with amblyopic observers but almost absent with normal observers. This study examined whether a reliable temporal crowding can be found for normal observers with peripheral presentation, and whether similar relations between temporal and spatial crowding will emerge. In three experiments, an RSVP of 3 displays was presented at 9° of eccentricity. Each RSVP's display included 1 (Experiment 1) or 3 (Experiments 2 & 3) letters. One of these displays included a target – an oriented T. Observers indicated the T's orientation. The ISI between the displays was systematically manipulated. Additionally, to determine the extent of spatial and temporal crowding simultaneously, in Experiments 2 & 3 the spacing between the target (the central letter) and its flankers was independently manipulated. As expected, we found spatial crowding: accuracy improved as the target-flankers spacing increased. This spatial crowding significantly interacted with target temporal position with in the RSVP stream, showing increased accuracy rates with later target positions. Critically, we also found temporal crowding in all 3 experiments: accuracy increased as the ISI between the displays increased. This effect was found even when only ISIs that are equal or larger than 150 ms were included, ensuring this ISI effect goes beyond basic backward or forward masking. Interestingly, the extent of this temporal crowding was larger for smaller target-flankers spacing (but only in Experiment 2), and was more pronounced when the target appeared at the first display. Hence, when the stimuli are presented at peripheral locations both spatial and temporal crowding can be demonstrated with normal observers.
Meeting abstract presented at VSS 2014
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