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Poster E2, Friday, November 10, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

The relationship between lexical development and neural measures of speech discrimination in monolingual and bilingual toddlers

Valerie Shafer1, Carol Tessel2, Michelle MacRoy-Higgins3, Nancy Vidal4, Yan Yu5, Alahna Cogburn1, Richard Schwartz1;1The Graduate Center, CUNY, 2Florida Atlantic University, 3Hunter College, 4Iona College, 5St. John's University

Considerable variability in rate of vocabulary growth is observed in first language acquisition. Some models of phonological development suggest that there is a strong relationship between the number of words in a child’s vocabulary and phonological development. For a child acquiring two languages, the relationship between vocabulary and phonology can be complex because the two languages often differ considerably in both phonology and vocabulary. The question addressed in this study is the relationship between language experience (input), lexical growth and phonological development in monolingual English and bilingual English-Spanish children. Behavioral measures of phonological and lexical development, and neural measures of speech perception were obtained from 10 monolingual and 10 bilingual children at multiple time points between six months and five years of age. Neural measures were collected form 65 electrode sites to an English-only vowel contrast (/I/ in ‘bit” versus /ε/ in “bet”) in an oddball paradigm designed to elicit the mismatch negativity (MMN) and neural measures of stimulus encoding (e.g., T-complex). Vocabulary was estimated from the MacArthur communicative development inventories and from 30-minute language samples. Language input was measured from a Language Background Questionnaire asking parents to rate the amount of input in different contexts (e.g., home) and from different people (e.g., mother). Language outcome was measured using the English and Spanish Preschool Language Scales (PLS) and receptive vocabulary measures (Peabody PPVT and TVIP). Results revealed considerable variability in vocabulary size, with English receptive vocabularies on the MacArthur ranging from 7 to 111 at 12 months of age but similar group means. Between 18 and 27 months of age, monolingually-exposed children showed larger English productive vocabularies (range 56-709) than the bilinguals (range 7-448). Three bilingual children showed vocabulary growth below the 15th percentile, but two had strong Spanish vocabularies. Most of the English monolingual children had a clear MMN from 300 to 400 ms after onset of the English vowel change. In contrast, only three bilingual children showed an MMN and these children had larger English vocabularies than the bilingual children showing no MMN. Monolingual children also showed increasing positivity from 100-200 ms at the left temporal sites (T-complex) with increasing age to the frequent vowel stimulus, whereas bilingual children generally showed increasing negativity with increasing age. After three years of age, all but two of the children showed language scores in the normal range. These two children were bilingual; one exhibited age-appropriate scores in Spanish and the other performed poorly in both languages. Amount of Spanish input did not directly affect the results. The bilingual child with the largest MMN had a large vocabulary at 24 months, age-appropriate language scores in both English and Spanish and balanced input. The bilingual child with the lowest English language scores had a small English vocabulary, poor language scores in both languages, balanced English and Spanish input, and no MMN. These findings suggest that the MMN measure of English vowel discrimination at 24 months of age is more closely related to current English vocabulary size than to later-age English language outcomes.

Topic Area: Language Development

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