Vocabulary of 2-Year-Olds Learning English and an Additional Language: Norms and Effects of Linguistic Distance

The majority of the world’s children grow up learning two or more languages. The study of early bilingualism is central to current psycholinguistics, offering insights into issues such as transfer and interference in development. From an applied perspective, it poses a universal challenge to language assessment practices throughout childhood, as typically developing bilingual children usually underperform relative to monolingual norms when assessed in one language only. We measured vocabulary with Communicative Development Inventories for 372 24-month-old toddlers learning British English and one Additional Language out of a diverse set of 13 (Bengali, Cantonese, Dutch, French, German, Greek, Hindi-Urdu, Italian, Mandarin, Polish, Portuguese, Spanish and Welsh). We furthered theoretical understanding of bilingual development by showing, for the first time, that linguistic distance between the child’s two languages predicts vocabulary outcome, with phonological overlap related to expressive vocabulary, and word order typology and morphological complexity related to receptive vocabulary, in the Additional Language. Our study also has crucial clinical implications: we have developed the first bilingual norms for expressive and receptive vocabulary for 24-month-olds learning British English and an Additional Language. These norms were derived from factors identified as uniquely predicting CDI vocabulary measures: the relative amount of English versus the Additional Language in child-directed input and parental overheard speech, and infant gender. The resulting UKBTAT tool was able to accurately predict the English vocabulary of an additional group of 58 bilinguals learning an Additional Language outside our target range. This offers a pragmatic method for the assessment of children in the majority language when no tool exists in the Additional Language. Our findings also suggest that the effect of linguistic distance might extend beyond bilinguals’ acquisition of early vocabulary to encompass broader cognitive processes, and could constitute a key factor in the study of the debated bilingual advantage.

CONTENTS 7             I: INTRODUCTION Caroline Floccia, Thomas D. Sambrook, Claire Delle Luche, Rosa Kwok, Jeremy Goslin, Laurence White, Allegra Cattani, Emily Sullivan, Kirsten Abbot-Smith, Andrea Krott, Debbie Mills, Caroline Rowland, Judit Gervain, and Kim Plunkett 30           II: METHODS Caroline Floccia, Thomas D. Sambrook, Claire Delle Luche, Rosa Kwok, Jeremy Goslin, Laurence White, Allegra Cattani, Emily Sullivan, Kirsten Abbot-Smith, Andrea Krott, Debbie Mills, Caroline Rowland, Judit Gervain, and Kim Plunkett 43           III: ANALYSES AND RESULTS FOR STUDY 1: ESTIMATING THE EFFECT OF LINGUISTIC DISTANCE ON VOCABULARY DEVELOPMENT Caroline Floccia, Thomas D. Sambrook, Claire Delle Luche, Rosa Kwok, Jeremy Goslin, Laurence White, Allegra Cattani, Emily Sullivan, Kirsten Abbot-Smith, Andrea Krott, Debbie Mills, Caroline Rowland, Judit Gervain, and Kim Plunkett 61           IV: RESULTS FOR STUDIES 2 AND 3: THE UKBTAT MODEL AND ITS APPLICATION TO NONTARGET ADDITIONAL LANGUAGE LEARNERS Caroline Floccia, Thomas D. Sambrook, Claire Delle Luche, Rosa Kwok, Jeremy Goslin, Laurence White, Allegra Cattani, Emily Sullivan, Kirsten Abbot-Smith, Andrea Krott, Debbie Mills, Caroline Rowland, Judit Gervain, and Kim Plunkett 68           V: GENERAL DISCUSSION Caroline Floccia, Thomas D. Sambrook, Claire Delle Luche, Rosa Kwok, Jeremy Goslin, Laurence White, Allegra Cattani, Emily Sullivan, Kirsten Abbot-Smith, Andrea Krott, Debbie Mills, Caroline Rowland, Judit Gervain, and Kim Plunkett 81           APPENDIX 91           REFERENCES 109        ACKNOWLEDGMENTS COMMENTARY 110        ADVANCES IN THE ASSESSMENT OF YOUNG BILINGUALS: COMMENTS ON FLOCCIA ET AL. Erika Hoff and Cynthia Core 124        CONTRIBUTORS 127        SUBJECT INDEX