Vocal communication between parents and infants.

Mothers and fathers of 20 boys and 20 girls representing all social classes were filmed when playing with their 6-month-old infants in a standardized playing situation. The vocal behavior of the parents and their infants was analyzed for sex differences. In addition, vocal activity was compared in parents and infants. Mothers showed a higher vocal activity than fathers together with their infants. Mothers also received more vocal activity from their infants than the fathers did. Fathers took more vocal initiatives towards girls than towards boys. Parents were vocally more active than infants. Comparing the vocal irritability of boys and girls, no differences were found. Fathers and mothers did not differ in vocal responsiveness to vocal irritability. Girls received more vocal initiations from fathers than boys while mothers treated boys and girls vocally equally.