Does size matter ? Subsegmental cues to vowel mispronunciation detection* NIVEDITA MANI University of Go ¨ttingen AND KIM PLUNKETT University of Oxford (Received 17 November 2008 – Revised 28 September 2009 – Accepted 18 April 2010 – First published online 1 November 2010) ABSTRACT Children look longer at a familiar object when presented with either correct pronunciations or small mispronunciations of consonants in the object’s label, but not following larger mispronunciations. The current article examines whether children display a similar graded sensitivity to different degrees of mispronunciations of the vowels in familiar words, by testing children’s sensitivity to 1-feature, 2-feature and 3-feature mispronunciations of the vowels of familiar labels : Children aged 1 ; 6 did not show a graded sensitivity to vowel mispronunciations, even when the trial length was increased to allow them more time to form a response. Two-year-olds displayed a robust sensitivity to increases in vowel mispronunciation size, differentiating between small and large mispronunciations. While this suggests that early lexical representations contain information about the features contributing to vocalic identity, we present evidence that this graded sensitivity is better explained by the acoustic characteristics of the different mispronunciation types presented to children. INTRODUCTION During the second year of life, infants demonstrate comprehension of a substantial repertoire of words. The average infant aged 1 ; 0 knows as many as 80 words, a number which increases rapidly to around 500 words by the [*] This research was supported by an ESRC grant RES-000-23-1322 awarded to Kim Plunkett. Address for correspondence : Nivedita Mani, Free-Floater (Junior) Research Group, ‘ Language Acquisition’, University of Go ¨ttingen, Gosslerstrasse, 14, 37073 Go ¨ttingen. e-mail : nmani@gwdg.de J. Child Lang. 38 (2011), 606–627. f Cambridge University Press 2010 doi:10.1017/S0305000910000243 606