Non-verbal rationality? 2-year-old children, dogs and pigs show unselective responses to unreliability, but to different degrees

Some philosophers argue that reflection is key to rational thinking. By tying reflective thinking to language, they struggle to account for minimally verbal infants and exclude non-human animals. This study assesses processing of undermining defeaters—a basic form of reflective thinking—in 36 two-year-old British children (13 female; 98% White), 39 dogs (18 female), and 21 pigs (9 female). Informants acted on two screens: one informant’s actions reliably indicated a rewarded location, while the other informant’s actions did not. Informants switched actions twice, prompting subjects to infer their reliability. Subjects’ willingness to follow the informant’s indications did not differ between the reliable and unreliable informants. However, reduced following in later trials suggests a response to uncertainty or an undermining defeater.