Effects of Selective Attention on Mean-Size Computation: Weighted Averaging and Perceptual Enlargement.

For efficient use of limited capacity, the visual system summarizes redundant information and prioritizes relevant information, strategies known respectively as ensemble perception and selective attention. Although previous studies showed a close relationship between these strategies, the specific mechanisms underlying the relationship have not been determined. We investigated how attention modulated mean-size computation. Fourteen people participated in this study. We hypothesized that attention biases mean-size computation by increasing the contribution (weighted averaging) and the apparent size (perceptual enlargement) of an attended item. Consistent with this hypothesis, our results showed that estimated mean sizes were biased toward the attended size and overestimated regardless of the attended size, supporting weighted averaging and perceptual enlargement, respectively. Taken together, the observed effects of selective attention on mean-size computation signify a close relationship between the two optimization mechanisms to achieve efficient management of the visual system's limited capacity.