Reverse asymmetry for whole-letter confusions in crowding H Strasburger1, M Malania2 |
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1Med. Psychology, U. München, U. Göttingen, Germany |
| Letter crowding is likely not a uniform process and several distinctions for its source have been proposed (letter confusion vs. letter substitution, within-character vs. between-character crowding, feature-source vs. letter-source confusion, and more). We re-analyzed our data from a three-letter contrast-threshold crowding paradigm with transient ring cue, with respect to inward-outward asymmetry of confusions of the target with a flanker. Testing was at three eccentricities (2, 4, and 6 deg) for a range of flanker distances and cue sizes in 20 subjects. The cue enhanced target contrast sensitivity but had no effect on flanker confusions. Surprisingly, confusions were asymmetric in a direction opposite to asymmetries reported for masking: The inward – not the outward – flanker was increasingly confused at increasing target eccentricities. The results support the above-mentioned distinctions of sources-to-crowding and suggest separate neural coding of pattern content and position, i.e., of what and where. The dependencies of confusions on flanker distance scale with eccentricity and are described by a generalized Bouma critical-separation rule. We propose underlying mechanisms to letter crowding where feature-binding decreases with eccentricity such that free-floating letter parts intrude from the periphery and whole letters from the center. |
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