Limitations on animacy categorization in ensemble perception
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Description: People can rapidly and efficiently categorize the animacy of individual objects and scenes, even with few visual features available. Does this necessarily mean that the visual system has an unlimited capacity to process animacy across the entire visual field? We tested this in an ensemble task requiring observers to judge the relative numerosity of animate vs. inanimate items in briefly presented sets of objects. We generated a set of morphed “animacy continua” between pairs of animal and inanimate object silhouettes and tested them in both individual object categorization and ensemble enumeration. For the ensemble task of Experiment 1, we manipulated the ratio between animate and inanimate items present in the display and used both “segmentable” (including only definitely animate and inanimate items) and “non-segmentable” (middle-value, ambiguous morphs pictures were shown along with the extremes) distributions of items. Experiment 2 manipulated feature discriminability both within color and animacy spaces to ensure the results were not based on different discriminability. We found that observers failed to integrate animacy information from multiple items, as they showed very poor performance in the ensemble task and were not sensitive to the distribution type -- despite their categorization rate for individual objects being near 100%. A control condition using the same design with color as a category-defining dimension elicited both good individual object and ensemble categorization performance and a strong effect of the segmentability type. We conclude that good individual categorization does not necessarily allow people to build ensemble animacy representations, thus showing the limited capacity of animacy perception.