High confidence and low accuracy in redundancy masking.

Visual scenes typically contain redundant information. One mechanism by which the visual system compresses such redundancies is 'redundancy masking' - the reduction of the perceived number of items in repeating patterns. For example, when presented with three lines in the periphery, observers frequently report only two lines. Redundancy masking is strong in radial arrangements and absent in tangential arrangements. Previous studies suggested that redundancy-masked percepts predominate in stimuli susceptible to redundancy masking. Here, we investigated whether strong redundancy masking is associated with high confidence in perceptual judgements. Observers viewed three to seven radially or tangentially arranged lines at 10° eccentricity. They first indicated the number of lines, and then rated their confidence in their responses. As expected, redundancy masking was strong in radial arrangements and weak in tangential arrangements. Importantly, with radial arrangements, observers were more confident in their responses when redundancy masking occurred (i.e., lower number of lines reported) than when it did not occur (i.e., correct number of lines reported). Hence, observers reported higher confidence for erroneous than for correct judgments. In contrast, with tangential arrangements, observers were similarly confident in their responses whether redundancy masking occurred or not. The inversion of confidence in the radial condition (higher confidence when accuracy was low and lower confidence when accuracy was high) suggests that redundancy-masked appearance trumps 'veridical' perception. The often-reported richness of visual consciousness may partly be due to overconfidence in erroneous judgments in visual scenes that are subject to redundancy masking.