Compression of redundant visual information improves feature discrimination in human vision

The visual environment contains more information than can be fully processed. To cope with this information, the visual system selects, integrates, and compresses sensory inputs. These processes are particularly evident in peripheral vision, where nearby items strongly limit access to individual elements, as in crowding and redundancy masking. In redundancy masking, repeated items are compressed into fewer items than are physically present, for example, three spatially separated items presented in the periphery are often perceived as only two items. Whether these interactions among items merely limit access to visual information or serve a functional role in perception remains unknown. Here, we investigated whether redundancy masking, despite reducing the number of perceived items, improves feature discrimination. In two experiments, participants viewed arrays of identical bars in peripheral vision, reported the number of bars they perceived, and adjusted a foveal probe to match perceived width (Experiment 1) or width and spacing (Experiment 2). Strong redundancy masking occurred in both experiments. When participants perceived fewer bars than were presented, perceived width was closer to the presented bar width than when all bars were perceived, where width was systematically underestimated. In Experiment 2, the perceived spacing between the (fewer) perceived bars increased. We modeled feature discrimination under redundancy masking and found that the observed improvement could not be explained by averaging features of the lost and perceived bars. These results suggest that the visual system efficiently compresses redundant information, reducing the number of perceived items while improving feature discrimination.