engleski

Lexical diversity in bilingual speakers of Croatian and Italian

The need to examine bilingual lexical development across both languages can be challenging, especially for languages where none or few standardised tests are available. Language samples, i.e. transcribed recordings of spoken language, provide an alternative to standardised language assessment. Observing how results obtained from language samples analyses correspond to those retrieved with tests of language knowledge might benefit research in languages with a lack of standardised language assessment materials. This would serve a growing need for reliable procedures for discriminating between bilinguals with typical development and bilinguals with language disorder in a situation where there are no tests or only monolingually normed tests are available. Longstanding, widely used measures of lexical development (LD) based on language samples are number of different words (NDW) and number of lemmas (NLW). These measures served as the basis for the first index of lexical diversity, the type-token ratio (TTR - Templin, 1957). All these measures are highly sensitive to text length, so researchers have attempted to correct for differences in sample length developing a number of other measures of lexical diversity (overview: Malveren et al., 2004 ; McCarthy & Jarvis, 2007 ; deBoer, 2014 ; Fergadiotis et al., 2015). The present study applied two methodologies, language testing and several lexical diversity measures to assess the vocabulary knowledge of bilingual children speaking Italian and Croatian and compare them to monolingual peers. The aim of this study was to determine whether measures of lexical diversity (LD) can be used to assess general lexical knowledge. The study focused on 30 sequential Croatian/Italian bilinguals aged between 5 and 7 years, that were compared to 30 Croatian and 30 Italian Monolinguals matched for age. LD was assessed from narrative language samples using standard measures and compared with Peabody Picture Vocabulary Test (PPVT) results. Two LD measures — the type-token ratio (TTR) and the measure proposed by Maas (1972) — did not differentiate between bilinguals and monolinguals, whereas several others did: number of different words (NDW), measure D, moving average type-token ratio (MATTR) and hypergeometric diversity of D (HD-D). NTW, NDW, D, MATTR and HD-D were predictive of PPVT results for monolinguals, whereas NDW, TNW and D (with replacements, Dr) were predictive of PPVT results for bilinguals. LD measures resulted to be reliable measures of bilinguals’ vocabulary knowledge reflecting adequately the results of PPVT in languages different from English. References: deBoer, F. (2014). Evaluating the comparability of two measures of lexical diversity. System, 47, 139-145. Fergadiotis, G., Wright, H., & Green, S. (2015). Psychometric evaluation of lexical diversity indices: Assessing length effects. Journal of Speech, Language, and Hearing Research, 58(3), 840-852. Malvern, D., Richards, B., Chipere, N., & Durán, P. (2004). Lexical diversity and language development. New York: Palgrave Macmillan. McCarthy, P.M., & Jarvis, S. (2010). MTLD, vocd-D, and HD-D: A validation study of sophisticated approaches to lexical diversity assessment. Behavior Research Methods, 42(2), 381-392. Templin M. C. (1957). Certain language skills in children. Minneapolis: University of Minnesota Press.

bilinguals, lexical divesity, typological differences

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