In this paper, we summarize a series of studies on the developmental changes in social cognition in mother-raised infant chimpanzees from birth to around 2 years old. The infants preferentially tracked a photograph of their mother's face at 1 month but showed indifferent preferences to faces at 2 months old. This change in facial recognition was correlated with a decrease in neonatal spontaneous smiling, increase in social smiling and a decline in neonatal imitation of facial expressions. Also at around 2 months, the infants began to show preferences for directed-gaze faces over averted gazes, and the amount of mutual gaze time between mother and infant chimpanzees increased. Thus, by 2 months of age, abilities required for dyadic interactions are already developed in chimpanzees as is the case in humans. The development of triadic interactions, however, is rather different between these two species. The infant chimpanzee can follow another's pointing or gaze at around 1 year, but even by 2 years old, does not “share” attention with the others.
Tomonaga, M., Tanaka, M., Matsuzawa, T., Myowa-Yamakoshi, M., Kosugi, D., Mizuno, Y., Okamoto, S., Yamaguchi, M. K., & Bard, K. A. (2004). Development of social cognition in infant chimpanzees (Pan troglodytes): Face recognition, smiling, mutual gaze, gaze following, and the lack of triadic interactions. Japanese Psychological Research, 46, 227-235. https://doi.org/10.1111/j.1468-5584.2004.00254.x