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Abstract

Several species can detect when they are uncertain about what decision tomake—revealed by opting out of the choice, or by seeking more informationbefore deciding. However, we do not know whether any nonhuman animalsrecognize when they need more information to make a decision because newevidence contradicts an already-formed belief. Here, we explore this abilityin great apes and human children. First, we show that after great apes sawnew evidence contradicting their belief about which of two rewards wasgreater, they stopped to recheck the evidence for their belief beforedeciding. This indicates the ability to keep track of the reasons for theirdecisions, or’rational monitoring’of the decision-making process. Childrendid the same at 5 years of age, but not at 3 years. In a second study, partici-pants formed a belief about a reward’s location, but then a social partnercontradicted them, by picking the opposite location. This time even 3-year-old children rechecked the evidence, while apes ignored the disagree-ment. While apes were sensitive only to the conflict in physical evidence,the youngest children were more sensitive to peer disagreement than con-flicting physical evidence.