The Common Format Hypothesis: The Central Form Integrates Causal Information from Different Domains into a Common Format

This paper investigates the structure of human concepts, proposing and testing the Common Format Hypothesis. According to this hypothesis, all concepts share a central form—a domain-general structure that encodes their conceptual identity—while causal knowledge remains domain-specific. Across three experiments, participants learned about novel categories and their properties, with properties introduced either as satisfying a causal schema (which varied by domain) or as central form properties. The studies then tested the immediate activation of strong property-focused beliefs—specifically, beliefs about certainty, normativity, and permanence. Results showed that while participants sometimes used causal cues to guide form encoding, they only exhibited these strong beliefs when a property had been encoded as part of the central form. This pattern held across domains (animals and artifacts), despite different causal structures. These findings support the Common Format Hypothesis and offer new insight into conceptual combination, linguistic creativity, and concept learning.