Persistence suggests metacognition in capuchin monkeys

Abstract

Awareness of one's own mental states, also known as metacognition, is an important component of human self-awareness. In recent decades, several studies have investigated nonhuman metacognition and evidence of this ability has notably been gathered in catarrhine primates. Conversely, numerous studies on capuchin monkeys have reported mixed or negative results. Because it has been suggested that the failure of capuchins may be due to species-related limitations of classical metacognition tasks, we tested metacognition in the brown capuchin, Sapajus apella, using a novel experimental paradigm adapted from a study of human infants. In this experiment, capuchins had to choose between two boxes, one of which had previously been baited with a treat under their gaze, before searching the hidden content of the chosen box. As the treat was surreptitiously removed, the time capuchins were willing to search the box for the treat could be used as a nonverbal postdecision indicator of metacognitive confidence, with longer persistence times indicating greater confidence in remembering which box was baited and expecting to find the treat in the chosen box. Consistent with the possibility that capuchins possess metacognitive abilities, capuchins persisted longer in their search after a correct versus incorrect choice. This result suggests that metacognition in primates is not restricted to catarrhines. Although nonmetacognitive explanations are possible, experimental paradigms involving a postdecision indicator of confidence, such as persistence, have advantages over classical paradigms and offer promising perspectives for investigating metacognition in a wide range of animals.