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Lexical Richness in the Spontaneous Speech of Bilinguals

Daller, Helmut; Van Hout, Roeland; Treffers-D Aller, Jeanine


Helmut Daller

Roeland Van Hout

Jeanine Treffers-D Aller


The focus of the present paper is on the measurement of lexical richness. Lexical richness is often measured either by the traditional type-token ratio (TTR) or by its square root variant, the index of Guiraud. The disadvantages of these measures, especially those of the TTR, are well-known. In this paper we propose two measures (Advanced TTR and Guiraud Advanced) that have clear advantages over the traditional measures. These two measures combine characteristics of type/token related measures with the notion of different layers of frequency/productivity in the lexicon (see Laufer and Nation 1995). We computed indices for the lexical items used in an oral text production task by two groups of Turkish-German bilinguals. One group has a German dominant bilingual competence; the other group consists of Turkish dominant bilinguals. It will be shown that the proposed measures for advanced lexical richness trace the characteristics of the bilingual profiles of the groups of subjects better than the traditional measures. Since the two languages involved in this study are typologically quite different, the additional technique of standardizing scores (z scores) was required to draw comparisons between the two languages. The conclusion is that the two proposed indices of advanced lexical richness, and especially the Guiraud Advanced, yield the clearest results. The new measures can be readily computed and are useful in the context of linguistic research as well as in classroom settings.


Daller, H., Van Hout, R., & Treffers-D Aller, J. (2003). Lexical Richness in the Spontaneous Speech of Bilinguals. Applied Linguistics, 24(2), 197-222+267.

Journal Article Type Review
Publication Date Jun 1, 2003
Journal Applied Linguistics
Print ISSN 0142-6001
Publisher Oxford University Press (OUP)
Peer Reviewed Not Peer Reviewed
Volume 24
Issue 2
Pages 197-222+267
Keywords bilingual, lexicon, spontaneous speech
Public URL
Publisher URL
Additional Information Additional Information : This article presents a new analysis of lexical richness in a bilingual setting. Its originality resides in the fact that different groups of bilinguals are compared with each other and not only with monolinguals as is often the case in studies of bilinguals. In his role of first author, Daller led the data collection and the analysis, developed a new measure of lexical richness, the Advanced Guiraud, and wrote the article, while Van Hout contributed towards the statistical analysis of the data and Treffers-Daller towards the analysis of frequency data and the collection of teacher judgements in Turkish. Daller also led the revision of the article, following comments from the reviewers of Applied Linguistics. Since the publication of this article the new measure Advanced Guiraud has been referred to by researchers working on a wide variety of languages (including Japanese and Mandarin). McCarthy and Jarvis (2007) in their in Language Testing mention Daller et al's article as one of the nine major studies on reliability of lexical diversity measures since 1993.

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