In WEIRD (Western, educated, industrialized, rich, democratic) societies, face-to-face interactions are an important component of mother-infant interactions. While facing each other, they engage in a variety of non-verbal means of communication, including facial expressions, such as smiles, and eye contact. It has been suggested that face-to-face interactions are unique to humans, as they are a form of emotional communication indicative of the long-lasting bond between mothers and their infants.
However, other great apes, including the closest relatives of humans, the chimpanzees, also form close and long-lasting relationships with their offspring, but little is known about the role of face-to-face contact in mother-infant interactions. In terms of quantitative measures, research has shown that gazing bouts in chimpanzees are shorter than in human mother-infant dyads. However, less is known about the quality of such face-to-face contact, as it remains an open question what chimpanzee mothers or their infants do while engaging in such interactions.
Therefore, the group studied face-to-face contact between mothers and their infants in captive chimpanzees and humans from a Western society, to investigate both qualitative and quantitative aspects of their face-to-face interactions. They predicted that 1) human mothers spend more time engaging in face-to-face contact with their infants, and 2) both species vary with regard to the types of behaviours used during such gazing bouts. They used focal observations to video-record spontaneous interactions of ten human and 8 chimpanzee mothers and their 6-months-old infants, and coded facial expressions, facial touches, and the duration of face-to-face contact. If feasible, eye contact was also coded. As predicted, human dyads spend significantly more time in face-to-face interactions than chimpanzees. Species also differed with regard to the behaviours shown during face-to-face contact: human mothers frequently engaged in direct eye contact and to some extent, also mirrored facial expressions of their infant, while chimpanzee mothers often touched the face of their infants, eg, during grooming bouts. Thus, these findings indicate that during face-to-face contact, human mothers use different behaviors to communicate with their infants, while in chimpanzees face-to-face contact seems to be rather a by-product of the mother’s bodily actions on the infant, rather than a communicative situation.