The pitch of maternal voice: a comparison of mothers suffering from depressed mood and non-depressed mothers reading books to their infants.

BACKGROUND: Research suggests that storybook reading promotes language development and that there is a relationship between maternal affective responses in relation to infant affect and language development. The purpose of this study is to relate maternal paralinguistic and verbal behaviour during storybook reading to maternal mood state.
METHOD: Mothers (n = 32) reporting depressed mood (as measured by the Edinburgh Postnatal Depression Scale) were matched on age of baby (mean age = 6 months, mean age = 10 months), sex of baby, educational status of mother and parity with 32 non-depressed mothers. They were video- and audio-taped in their homes while reading a picture-book to their infants. Maternal textual and extra-textual utterances were transcribed and analysed in terms of mean length utterance (MLU), fundamental frequency and pitch modulation.
RESULTS: There was an interaction between psychological well being and age group with regard to MLU for text read. Non-depressed mothers had a smaller MLU for younger babies in comparison with older babies, while depressed mothers showed no difference in their MLU. There was a main effect of psychological well being with depressed mothers speaking with a higher mean pitch and more modulations in their pitch, in comparison with non-depressed mothers. Furthermore, there was a significant interaction of the psychological well being of the mother and the mean fundamental frequency used when reading the text and when speaking to their child during the picture-book session.
CONCLUSIONS: These differences in maternal speech indicate that mothers who are depressed are less attuned to their infants which might force the infant into self-regulatory patterns that eventually compromise the child's development.