title: Phonetic modification of vowel space in storybook speech to infants up to 2 years of age.
abstract: OBJECTIVE
  A large body of literature has indicated vowel space area expansion in infant-directed (ID) speech compared with adult-directed (AD) speech, which may promote language acquisition. The current study tested whether this expansion occurs in storybook speech read to infants at various points during their first 2 years of life.
  
  
  METHODS
  In 2 studies, mothers read a storybook containing target vowels in ID and AD speech conditions. Study 1 was longitudinal, with 11 mothers recorded when their infants were 3, 6, and 9 months old. Study 2 was cross-sectional, with 48 mothers recorded when their infants were 3, 9, 13, or 20 months old (n=12 per group). The 1st and 2nd formants of vowels /i/, /ɑ/, and /u/ were measured, and vowel space area and dispersion were calculated.
  
  
  RESULTS
  Across both studies, 1st and/or 2nd formant frequencies shifted systematically for /i/ and /u/ vowels in ID compared with AD speech. No difference in vowel space area or dispersion was found.
  
  
  CONCLUSIONS
  The results suggest that a variety of communication and situational factors may affect phonetic modifications in ID speech, but that vowel space characteristics in speech to infants stay consistent across the first 2 years of life.
authors: Evamarie B
authors: EB
authors: Burnham
authors: Elizabeth A
authors: EA
authors: Wieland
authors: Maria V
authors: MV
authors: Kondaurova
authors: J Devin
authors: JD
authors: McAuley
authors: Tonya R
authors: TR
authors: Bergeson
authors: Laura C
authors: LC
authors: Dilley
mesh_terms: D000328:Adult; D002663:Child Language; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D009035:Mothers; D010700:Phonetics; D011932:Reading; D013061:Speech Acoustics; D013067:Speech Perception