Core Intuitions of Psychological Non-Contradiction: Infants Assume That Individual Agents Act and Communicate Coherently.

Humans generally posit that contrary mental states are unlikely to co-exist within a single mind. We tested the early ontogeny of this assumption in two domains: action and communication. Studies 1A and 1B tested whether 9-month-old infants assume that agents act coherently. Infants watched interactions between two hands whose owner(s) were invisible. In the contrary goals condition, the hand performed contrary actions-one hand reached for an object while the other impeded it. Later, during test trials, infants learned that the hands belonged to one or two people. Looking-time patterns across the contrary goals and a baseline conditions indicated that clear goal conflict led infants to infer two agents, suggesting they viewed it as unlikely for a single person to thwart their own goal. Study 2 tested whether infants assume communicative coherence, testing whether they assume that a single informant is unlikely to entertain and communicate conflicting information while two informants might do so. Informants pointed to indicate a toy's location to 15-month-olds. When two different informants each pointed to a different place, infants did not follow one pointing gesture more than the other. However, when a single informant pointed successively to two locations, infants followed the second gesture, implying they viewed it as an updated, not contradictory, message. Thus, infants assumed that a single informant is unlikely to contradict themselves (i.e., by asserting that a toy is simultaneously in two locations). These findings reveal an early-emerging assumption of psychological coherence in infants' representation of other minds, across both action and communication contexts.