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, and 21 pigs. Subjects observed informants act on two screens: one informant’s actions reliably indicated the reward location, while the others did not. Twice informants switched actions, prompting subjects to infer the reliability of the informants. Subjects did not respond differently to the Reliable and Unreliable informants. However, reduced willingness to follow informants’ indications in later trials suggests a response to uncertainty or an undermining defeater.