Proceedings of the Annual Meeting of the Cognitive Science Society

Infant directed speech (IDS) is characterized by exaggerated pitch and vowel lengthening. The current study recorded ev-eryday interactions with fifty 12-month-old infants and their families to examine whether there are significant differencesin the acoustic features of IDS (such as frequency, pause duration, and vowel length) between male and female speak-ers, and whether any differences are related to childrens vocabulary development at 12 months and 15 months. Femalespeakers, compared with male speakers, exhibited significantly longer pauses in phrase final positions, thereby poten-tially signaling syntactic structures more clearly. Controlling for family income and maternal education, female speakersfrequency variation at non-final vowel positions accounted for an additional unique variance for infants productive vocab-ulary at 12 months and receptive vocabulary at 15 months while none of the acoustic features of male speakers related tovocabulary size. These results suggest that female speakers IDS may be more influential in language development.