Bodily Self in Macaque Monkeys and Human Infants

Whether monkeys possess the concept of bodily self remains controversial. We found that macaque monkeys trained for mirror self-recognition (MSR) could spontaneously recognize themselves when viewing video images of their back from a third-person perspective (3PP), but this generalization required a few minutes of "exploration". In contrast, through visual-tactile synchronization training similar to that used in human out-of-body studies, naive monkeys could recognize themselves from 3PP back images and demonstrated MSR within seconds. Interestingly, in human infants, we found that 3PP back self-recognition developed spontaneously several months after MSR. These results demonstrate the existence of hierarchical bodily self in macaques and similar stepwise development of bodily self in human infants, offering insights into the emergence and manifestation of bodily self in natural and artificial intelligence.