Much of human communication and collaboration is predicated on making predictions about others' actions. Humans frequently use predictions about others' action mistakes to correct others and spare them mistakes. Such anticipatory correcting reveals a social motivation for unsolicited helping. Cognitively, it requires forward inferences about others' actions through mental attributions of goal and reality representations. The current study shows that infants spontaneously intervene when an adult is mistaken about the location of an object she is about to retrieve. Infants pointed out a correct location for an adult before she was about to commit a mistake. Infants did not intervene in control conditions when the adult had witnessed the misplacement, or when she did not intend to retrieve the misplaced object. Results suggest that preverbal infants anticipate a person's mistaken action through mental attributions of both her goal and reality representations, and correct her proactively by spontaneously providing unsolicited information.