Mothers' and infants' responses to their partners' spontaneous action and vocal/verbal imitation.

Twenty mother-infant dyads (10 boys, 10 girls) were videotaped longitudinally at ages 10, 13, 17, and 21 months during in-home free play and bath sessions. Mothers' and infants' responses to their partners' naturally occurring action and vocal/verbal imitations were described, and relations to infants' imitation rates and vocabularies were examined. Mothers' response rates were consistently high and unrelated to infants' imitation rates. As early as 10 months, infants responded to the great majority of maternal imitations, especially action imitations, often with actions. Infants' return imitations to action matching indicated increasing awareness of being imitated. Infants' responses to mothers' vocal/verbal imitation were associated with their later vocabulary levels. Children who would be more lexically advanced at 17 and/or 21 months provided more social responses at 10 months, more socially responsive actions and return verbal imitations at 13 months, and more non-imitative socially responsive words at 17 and 21 months.