Infants use logic to reduce uncertainty in learning

Are infants guided by logic in thinking and learning? We show that in diverse contexts characterized by the presence of possible alternatives -- for example, when an object can be in location A or location B, or when an unknown word can refer to either object A or object B -- signatures of reasoning emerge in 19-month-olds: infants are guided by logical strategies (i.e., it cannot be A, therefore it has to be B). Even in a linguistic task such as word learning, markers of logical reasoning surfaced both in bilinguals and monolinguals, suggesting that reasoning is not fundamentally influenced by language acquisition but, rather, helps language acquisition. Our work shows that early learning is crucially supported by fundamental mechanisms of dealing with uncertainty reasoning by exclusion has a widespread role. Like other forms of reasoning, this tiny bit of deduction has the effect of reducing uncertainty by eliminating possibilities, adding a piece to the mosaic of rational strategies that infants deploy to consolidate their developing knowledge of the world.