A cross-cultural comparison of the development of the social smile

► Münster is a socio-cultural community with a lot of face-to-face interactions. ► Nso is a socio-cultural community with a few face-to-face interactions. ► When infants were 12 weeks old Mothers from Münster imitated their infants' smile more frequently and infants imitated maternal smile more often than did Nso mothers and infants. ► Infants from Münster showed more social smile with 12 weeks than did Nso infants. ► Both maternal and infant imitations determine the emergence of the social smile.