Category selectivity for animals and man-made objects: Beyond low- and mid-level visual features

Distinct concepts, such as animate and inanimate entities, comprise vast and systematic differences in visual features. While observers search for animals faster than man-made objects, it remains unclear to what extent visual or conceptual information contributes to such differences in visual search performance. Previous studies demonstrated that visual features are likely sufficient for distinguishing animals from man-made objects. Across four experiments, we examined whether low- or mid-level visual features solely contribute to the search advantage for animals by using images of comparable visual shape and gist statistics across the categories. Participants searched for either animal or man-made object targets on a multiple-item display with fruit/vegetable distractors. We consistently observed faster search performance for animal than man-made object targets. Such advantage for animals was unlikely affected by differences in low- or mid-level visual properties or whether observers were either explicitly told about the specific targets or not explicitly told to search for either animals or man-made objects. Instead, the efficiency in categorizing animals over man-made objects appeared to contribute to the search advantage. We suggest that apart from low- or mid-level visual differences among categories, higher-order processes, such as categorization via interpreting visual inputs and mapping them onto distinct concepts, may be critical in shaping category-selective effects.