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 singlemind. We tested the early ontogeny of this assumption in two domains: action andcommunication. Studies 1A and 1B tested whether 9-month-old infants assume that agents actcoherently. Infants watched interactions between two hands whose owner(s) were invisible. Inthe contrary goals condition, the hand performed contrary actions-one hand reached for anobject while the other impeded it. Later, during test trials, infants learned that the handsbelonged to one or two people. Looking-time patterns across the contrary goals and a baselineconditions indicated that clear goal conflict led infants to infer two agents, suggesting theyviewed it as unlikely for a single person to thwart their own goal. Study 2 tested whetherinfants assume communicative coherence, testing whether they assume that a single informantis unlikely to entertain and communicate conflicting information while two informants mightdo so. Informants pointed to indicate a toy's location to 15-month-olds. When two differentinformants each pointed to a different place, infants did not follow one pointing gesture morethan 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 anearly-emerging assumption of psychological coherence in infants'representation of otherminds, across both action and communication contexts