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Word learning, Phonology, Prosody, Tone, Language development


To efficiently recognize words, children learning an intonational language like English should avoid interpreting pitch-contour variation as signaling lexical contrast, despite the relevance of pitch at other levels of structure. Thus far, the developmental time-course with which English-learning children rule out pitch as a contrastive feature has been incompletely characterized. Prior studies have tested diverse lexical contrasts and have not tested beyond 30 months. To specify the developmental trajectory over a broader age range, we extended a prior study (Quam & Swingley, 2010), in which 30-month-olds and adults disregarded pitch changes, but attended to vowel changes, in newly learned words. Using the same phonological contrasts, we tested 3- to 5-year-olds, 24-month-olds, and 18-month-olds. The older two groups were tested using the language-guided-looking method. The oldest group attended to vowels but not pitch. Surprisingly, 24-month-olds ignored not just pitch but sometimes vowels as well—conflicting with prior findings of phonological constraint at 24 months. The youngest group was tested using the Switch habituation method, half with additional phonetic variability in training. Eighteen-month-olds learned both pitch-contrasted and vowel-contrasted words, whether or not additional variability was present. Thus, native-language phonological constraint was not evidenced prior to 30 months (Quam & Swingley, 2010). Given the surprising insensitivity to mispronunciations at 24 months, we tested 24-month-olds in two additional experiments, which are reported in Supplemental Materials. Experiment S1 tested 24-month-olds in the low-variability condition of the Switch procedure used at 18 months, finding that—in contrast to 18-month-olds—24-month-olds did not detect switches to the trained word-object pairings when the switches involved either a pitch change or a vowel change. Experiment S2 again used Switch habituation training, but tested children in a language-guided looking test instead of a Switch test (Yoshida, Fennell, Swingley, & Werker, 2009). Again, 24-month-olds showed no evidence of detecting subtle differences in word pronunciations. The data from all five experiments (1, 2, 3, S1, S2) are included in the data files in the interests of transparency.



This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made. © 2024 The Authors. Infancy published by Wiley Periodicals LLC on behalf of International Congress of Infant Studies.



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