Purity and Disgust: Same Domain, or Separate Mechanisms?


We argue that much recent literature on disgust, dirtiness and purity has been guilty of conflating two evolved mechanisms: an oral disgust mechanism aimed at avoiding the ingestion of dangerous substances, and a self-grooming (cleanliness) mechanism aimed at eliminating ectoparasites from the skin. Though phylogenetically distinct, these two mechanisms become associated in human ontogeny due to their similar targets and overlapping image schemas: one focused on the mouth, the other on the body as a whole. We show that several puzzles in the literature on disgust and moral purity can be resolved using this model. The idea of contamination so central to purity norms may more plausibly be based on grooming responses to ectoparasites than on disgust responses to endoparasites. The disgust image schema may more easily be extended to moral judgements about others, while the cleanliness schema is more easily extended to judgements about the self, with interesting consequences.

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