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Einat Rashal, Yaffa Yeshurun; Temporal crowding with normal observers and its interplay with spatial crowding. Journal of Vision 2010;10(7):1343. doi: 10.1167/10.7.1343.
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Spatial crowding refers to cases in which a target is flanked by other stimuli presented simultaneously with the target, and temporal crowding refers to cases in which the target is surrounded in time by other stimuli (i.e., stimuli that appear before and after the target). Recently, Bonneh, Sagi and Polat (2007) have demonstrated that temporal and spatial crowding in amblyopic observers are interrelated. However, only low crowding was found for their normal group, possibly due to foveal presentation. This study examined whether similar relations between temporal and spatial crowding can be found for normal observers with peripheral presentation. To measure simultaneously both temporal and spatial crowding, a rapid sequence of 3 displays was presented on a given trial at 9° of eccentricity. Each display included 3 letters. In one of these displays, the central letter was an oriented T, and the observers had to indicate the T's orientation. The spatial distance between the T and its flankers and the temporal spacing (ISI) between the displays was systematically manipulated to determine the extent of spatial and temporal crowding when measured concurrently. As expected we found spatial crowding: accuracy improved as the target-flankers spacing increased. This spatial crowding emerged regardless of the target temporal position but it significantly interacted with ISI: the effect was more pronounced at shorter ISIs. We also found temporal crowding: accuracy increased as the ISI between the displays increased, though this effect was considerably smaller than the spatial effect. Interestingly, the extent of this temporal crowding was larger for smaller target-flankers spacing and was more pronounced when the target appeared at the first temporal position. Hence, when the stimuli are presented at peripheral locations both spatial and temporal crowding can be demonstrated with normal observers. Moreover, as with amblyopic observers, these two types of crowding interact.
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