Fig. 3.

Performance thresholds. (a) Threshold tracking speed for near targets (open bars) and far targets (filled bars) separated by the vertical meridian and horizontal meridian. Thresholds were slower for near targets across both the vertical and horizontal meridians. (b) Threshold tracking speed as a function of target location in the visual field. Threshold speeds were slower when the targets appeared within the same quadrant (BR, bottom right; BL, bottom left; TR, top right; TL, top left) than when the targets were the same distance apart but appeared in separate quadrants (B, bottom; T, top; L, left; R, right).