Findings of a series of studies on individual differences and maturational changes in expressivity at the neonatal stage and during early infancy are reported. Research results indicate that newborns are able to discriminate and imitate the basic emotional expressions: happy, sad, and surprised. Results show widened infant lips when the happy expression is modeled, pouting lips when a sad face is modeled, and a widely opened mouth and widened eyes in response to a surprised face. Even preterm infants as young as 32 weeks of age can imitate these facial expressions. Like adults, however, some infants are very expressive and some are poker-faced. Monozygotic twins show discrimination and imitation abilities that are more similar than those of dizygotic twins. It is concluded that these data suggest a genetic predisposition for varying degrees of emotional expressivity that appear as early as birth. (RH)