Mother tongue - Phonetic Aspects of Infant-Directed Speech
Abstract: Phonetic aspects of mother-infant interaction are discussed in light of a functionalist Mother-infant phonetic interaction (MIPhI) model. Adults addressing infants typically use a speech style (infant-directed speech, IDS) characterized by, for instance, extensive suprasegmental (prosodic) modulations. This type of speech seems to interest young infants whose active experience with the spoken language appears to focus their speech perception on the phonological properties of the ambient language during the first year of life.This thesis consists of four articles discussing phonetic modifications at the suprasegmental, segmental and phonological levels, based on data from six Swedish mothersí IDS to their 3-month-olds. The first study concerns the tonal word accent 2 in disyllabic words, and shows how the lexical, bimodal, tonal characteristics of this accent are enhanced in IDS as compared to adult-directed speech (ADS). The second is a cross-linguistic investigation of vowel formant frequencies in Swedish, Am. English and Russian IDS. It shows that vowels like /i/, /u/, and /a/ are more clearly separated in IDS than in ADS, in all three languages. The third study addresses the voiced /voiceless contrast in stop consonants as measured by voice onset time (VOT) and shows that stop consonants seem to be poorly separated in early IDS samples. The fourth study investigates the quantity distinction in V:C and VC: sequences and indicates that this phonological contrast is well maintained in the IDS.Adult data are discussed within the MIPhI model, assuming that suprasegmental and segmental specifications in IDS follow different phonetic specification paths adapted to the infantsí capacities as these develop over the first 18 months of life. The adultsí phonetic adaptations appear to reflect a selective strategy of presenting linguistic structure in a ìgift-wrappingî that is attractive and functional for the infant.
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