A bridge between collinear inhibition and visual crowding: Hints from perceptual learning

Maniglia and colleagues reported a significant reduction in visual crowding following perceptual learning training on contrast detection using a lateral masking configuration with collinear flankers. They interpreted this reduction within a framework of shared cortical mechanisms between collinear inhibition, elicited by lateral masking with closely spaced flankers, and crowding. We reanalyzed their data to directly test this hypothesis by examining correlations between learning gains at short target-to-flankers separations (reduced contrast detection thresholds) and crowding reduction. Surprisingly, individual analyses revealed an inverse correlation: participants with greater reduction in collinear inhibition showed smaller reductions in crowding. We suggest that these participants exhibited separation-specific learning, which previous studies indicate may hinder effective transfer. Thus, while collinear inhibition and crowding may share mechanisms, distributed improvement across separations might be necessary to observe transfer of learning to crowding.