Changes in the Content and Prosody of Mothers' Speech to Infants Across the First Postnatal Year

The purpose of this research project was to examine the linguistic and prosodic content of infant-directed speech to infants, and to explore the relationship that exists between the prosodic features and the content of this speech, and how this relationship changes over the first eight months after birth. Analyses were conducted on maternal infant-directed speech directed to infants across three age groups: 1, 4, and 8-month olds. Speech samples were taken from 75 mothers (n = 25 per group) and both coded for content and analyzed for pitch (Fo) characteristics. Linguistic analysis indicated overall significantly more Informational speech that either Affective or Contentless speech directed to infants in all three age groups. In addition, significant differences were found within and between Affective and Contentless speech, but these effects were also mediated by age. Significant differences were also found in the acoustic features of maternal infant-directed speech, mediated by both type of speech and age. Overall, these results suggest that maternal infant-directed speech varies in both linguistic content and prosodic features, and that the variation of these prosodic features is mediated by both the type of speech used and the age of the infant.