Integration and segmentation conflict during ensemble coding of shape

During ensemble coding, the visual system extracts summary information from input that has been integrated, facilitating gist-level judgments about objects and features that belong together. In contrast, input can be segmented, allowing for quick categorical distinctions between objects. Integration and segmentation usually work in parallel but may sometimes conflict in the context of ensemble coding. To investigate this possibility, we examined summary perception of aspect ratio (i.e., "tallness/flatness"). Aspect ratio has a category boundary (e.g., a circle), and individual aspect ratios may be perceptually exaggerated-segmented-away from this boundary. We predicted that summary perception of multiple aspect ratios would be disrupted when, as a set, they spanned the category boundary, since integration and segmentation would then be at odds. We found that when observers reported the average aspect ratio of a set of ellipses, they were less sensitive to the mean of sets that included both tall and flat ellipses, compared to sets comprised of tall or flat ellipses. Follow-up experiments suggest this occurred because segmentation distorted the appearance of ellipses away from the category boundary, exaggerating set heterogeneity. These experiments advance understanding of how the visual system summarizes information by showing that integration and segmentation can conflict. (PsycInfo Database Record (c) 2020 APA, all rights reserved).