Supercrowding: weakly masking a target expands the range of crowding.

Crowding is impairment of peripheral object identification by nearby objects. Critical spacing (the minimum target-flanker distance that does not produce crowding) scales with target eccentricity and is consistently reported as roughly equal to or less than 50% of target eccentricity (0.5e). This study demonstrates that crowding occurs far beyond the typical critical spacing when the target is weakly masked by a surrounding contour or backwards pattern mask. A target was presented at a peripheral location on every trial and participants reported its orientation. Flankers appeared at target-flanker distances of 0.3-0.7e, or were absent. The target was presented with or without a mask. When flankers were absent, the masks only mildly impaired performance. When flankers were present but the mask was absent, target identification was nearly perfect at wide target-flanker distances (0.5e-0.7e). However, when flankers were present and the target was masked, performance dropped significantly, even when target-flanker distances far exceeded the typical crowding range. This phenomenon ("supercrowding") shares critical features with standard crowding: flankers similar to the target impair performance more than dissimilar flankers, and the characteristic anisotropic profile of crowding is preserved. Supercrowding may reflect a general interaction between crowding and other forms of masking.