Handl, A., Mahlberg, T., Norling, S., & Gredebäck, G. (2013) Facing still faces: What visual cues affect infants' observation of others? Infant Behaviour and Development

How 9-, 18-, and 24-month-old children looked at pictures of two people facing each other or standing back to back to each other. The children looked more often back and forth between the two actors when they faced each other. This means that they are able to use body orientation to understand more about others’ social interactions.