Meltzoff & Moore (1977) observed the beginnings of
interactional synchrony in infants as young as 2
weeks. An adult displayed one of three facial
expressions or one of three distinctive gestures.
The child’s response was filmed and identified by
independent observers. An association was found between the expression or gesture the adult had displayed and the actions of the babies.
In a later study Meltzoff & Moore (1983) demonstrated the same synchrony with infants only three days old.