Developmental trends in infant preferences for affective intent in mothers' speech

According to Kitamura & Burnham (2003), affective intent is modified in infant-directed (ID) speech such that mothers accentuate different emotional messages at different ages – ‘comforting’ at 3 months, ‘approving’ at 6 months, and ‘directive’ at 9 months. This study examined preferences for the three ID emotion types by infants aged 3, 6 and 9 months. After adults had rated utterances according to affective category, infants were tested with the 12 best exemplars using an auditory preference procedure. Results revealed that 3-month-olds preferred ‘comforting’ utterances; 6-month-olds preferred ‘approving’ to ‘directive’ ID utterances, and listened equally to ‘approving’ and ‘comforting’ utterances; and 9-month-olds showed no preference for any ID emotion type. Because it was possible that 9-month-olds were attending to segmental information, they were tested using low-pass filtered stimuli, and were found to prefer ‘directive’ to ‘comforting’ ID utterances, and listen equally to ‘directive’ and ‘approving’ utterances. It is concluded that during the first year, mothers’ speech not only relies on contingent responsiveness but is also affected by their infant’s age and state of development