Variability in vowel production by bilingual speakers: Can input properties hinder the early stabilization of contrastive categories?

Previous research has revealed differences between monolingual and bilingual toddlers in the process of stabilizing the categorization and phonological representation of some vowel contrasts. This phenomenon appears to be linked to input properties. The aim of the present study is to analyze whether differences in early language input conditions affect vowel productions in bilingual adults. Such evidence would have clear implications for the potential role of similar input conditions in young bilingual development. Two groups of Catalan–Spanish bilingual mothers participated in this study. They were fluent in Catalan and predominant Catalan-speakers at home, but differed in their linguistic environment as young learners (from Catalan-speaking homes (C-group), and from Spanish–Catalan bilingual homes or Spanish-speaking homes with an early exposure to Catalan (BSC-group)). Speech samples containing target words with Catalan mid-front vowels were recorded. Acoustical and error rate analyses were undertaken. Results revealed that both groups of participants had similar categories at the phonetic level, with only a minor difference in the acoustical dimensions of the /e/ vowel. However, at the lexical level, the BSC-group made frequent vowel category errors (producing /e/ in /ɛ/-target words). Variability and inconsistencies in vowel productions are, thus, input factors that should not be neglected in accounting for young bilinguals' protracted processes to stabilize and consolidate the representation of contrastive categories in their lexicon.

Research highlights▶ We analyzed mid-front Catalan vowels produced by adult bilingual speakers. ▶ Differences in exposure as a young learner affect vowel production in adulthood. ▶ Higher phonetic variability is found in speakers with an early bilingual exposure. ▶ Vowel category errors are observed in words produced by simultaneous bilinguals.