Effect of bilingualism on receptive and expressive vocabulary acquisition: Evidence from the MacArthur-Bates CDI

Previous studies suggested that very young bilinguals (below the age 1) have comparable receptive and fewer expressive vocabulary in comparison with monolingual peers. There is small evidence about the effect of second language exposure on first language development. Therefore the purpose of the study was to investigate the relationship between bilingualism and amount of second language exposure with acquisition of first language receptive and expressive vocabulary.Materials and Methods A sample of 43 bilingual and 341 monolingual infants between the ages of 0 and 30 months were collected. The MacArthur-Bates Communicative Development Inventory: Words and gestures (CDI-WG) was used to assess infant’s language development. Participants were equated on socioeconomic status and bilingual participants differed in the amount of exposure they had received to the second language.Poisson regression approach with count response variable was used to examine the correlates of number of receptive vocabulary and number of expressive vocabulary also prevalence ratios (PRs) were reported.Results Being bilingual was significantly associated with number of expressive vocabulary (PR= .21; P-value < 32333), however, it was not associated with number of receptive vocabulary (PR= 3290; P-value = 3.4.). Results in bilinguals showed that receptive and expressive vocabulary was significantly associated with hours that infants exposed to second language, respectively (PR=3230; P-value = 3232), (PR= 3212; P-value < 32333).Conclusions A strong relationship was found between the amount of exposure to a second language and performance in the first language. The relationship was stronger in expressive vocabulary which showed that the amount of second language exposure doesn’t affect the L3 receptive and expressive vocabulary in infancy. Contrary to previous studies, bilinguals had more expressive vocabulary in L3 than monolinguals and they didn’t show difference in receptive vocabulary. It can be suggested that bilingualism may not influence the L3 vocabulary acquisition, even, second language exposure may increase infant’s expressive vocabulary.