A triad oddity task was used to investigate developmental changes in perceived similarity among animals and humans. Four, five, seven, and eight year-old children and undergraduates were presented with triads consisting of a human, a non-human primate, and a non-primate animal, and asked about taxonomic similarity (ï¿½which two are the same kind of thing?ï¿½) and psychological similarity (ï¿½which two think and feel the same way?ï¿½). At all age groups, humans were seen as taxonomically unique. Beliefs about psychological similarity underwent marked developmental change, from essentially random guessing to belief that humans were psychologically unique to beliefs that humans were psychologically similar to other primates. There was little evidence of differentiation between psychological and taxonomic similarity among children. Younger childrenï¿½s responses were apparently guided solely by the human-nonhuman dichotomy, whereas older children and undergraduates were also influenced by the category mammal. Results suggest interesting continuities and discontinuities in the development of folk biological thought, and between folk and scientific biology.
KEYWORDS: similarity, folk biology, conceptual development.