Auditory-Visual Infant Directed Speech in Japanese and English

The aim of this project is to compare (i) the acoustic vs. visual characteristics of infant-directed speech (IDS), (ii) IDS vs adult-directed speech (ADS), and (iii) the acoustic/visual characteristics of IDS and ADS cross-linguistically, in Australian English (AusE) vs Japanese. Acoustic data are presented along with preliminary visual data. Native AusE and Japanese speaking mothers spoke to their 4- to 9-month-old infants and another adult using target words containing one of four vowels [a,i,u,o]. Results show higher F0 mean and greater F0 variation for IDS than ADS in both language groups, and longer vowel duration in IDS than ADS but this was only significantly so for the AusE mothers. Finally, there was a tendency for vowel hyper-articulation in AusE mothers IDS, but for vowel hypo-articulation in Japanese mothers IDS, and overall vowel hyperarticulation was greater in AusE than Japanese IDS. Preliminary visual data suggest that there appears to be, contrary to what would be expected, a substantial decrement in visual vowel lip area in Japanese IDS compared to ADS, a finding that is in concert with tendency for vowel hypo-articulation in Japanese than English IDS.