Between three and six months of age, the period of peak face-to-face play, an infant is exposed to tens of thousands of examples of facial emotions. In interactions with mother, a child mirrors mother's expression, and she, in turn, imitates the infant. The table below lists the infant's repertoire of facial emotions.

Emotion Description Emergence
Interest Brows knit or raised, mouth rounded, lips pursed Present at Birth
Distress Eyes closed tightly, mouth square and angular (as in anger) Present at Birth
Disgust Nose wrinkled, upper lip elevated, tongue protruded Present at Birth
Social smile Corners of mouth raised, cheeks lifted, eyes twinkle; neonatal "half smile" and early startle may be precursors 4 to 6 weeks
Anger Brows together and drawn downward, eyes set, mouth square 3 to 4 months
Sadness Inner corners of brows raised, mouth turns down in corners, pout 3 to 4 months
Surprise Brows raised, eyes widened, oval-shaped mouth 3 to 4 months
Fear Brows level but drawn in and up, eyes widened, mouth retracted 5-7 weeks

Source: Drawn from work of Carroll Izard as reported by Trotter (1983).