There are very early smiles with some infants. They may smile in their sleep or if they passed gas or pooped and now they feel better. But a social smile is when infants smile because they see a certain person’s face who makes them happy. Beginning at 6 to 9 weeks old infants will smile at certain people they like (Berger, 2018; Feldman, 2014).
Berger, K. S. (2018). The developing person: Through Childhood and adolescence (11th
ed.). New York, NY: Worth.
Feldman, R. S. (2014). Child development: A topical approach. Boston, MA: Pearson.