Fig. 1.

Procedures and sample data from experiment 1. (A) The time course of a sample trial. After a variable fixation period (0.2–1.4 s), three clock stimuli (not to scale) appeared in one of eight locations for 300 ms (flankers are depicted along the radial axis). Participants were required to fixate throughout the stimulus duration, to saccade to the white dot of the central target clock immediately after its offset, and to then indicate the orientation of the central target stroke. (B) Sample behavioral data from participant SP at 8° in the left visual field. Uncrowded performance is shown as the dashed gray line, and dark-green and light-green dots depict crowded performance with flankers on the radial and tangential dimensions, respectively. Cumulative Gaussian functions are fitted to crowded conditions; the dashed vertical arrow shows the critical spacing at which performance reaches 80% correct—values that defined the “crowding zone.” (C) An example 2D frequency distribution of saccade landing positions for participant JM at 4° in the left visual field. The cross shows the target location with the normalized frequency of saccade landing positions shown via the color-saturation scale. The saccade error zone was defined as an ellipse containing 80% of all saccade-landing errors, shown with the dashed black line.