ERP indices of speech processing in bilinguals

Abstract

The specific aim of this project was to examine perceptual differentiation of the vowel contrast [I-E] by early versus late bilingual Spanish–English speakers, compared to monolingual English speakers. Neither of these phonetic segments occur as phonemes in Spanish while they constitute phonemic contrast in English. For Spanish listeners, these vowels may be heard as variants of the Spanish phonemes [i] and [e], respectively. The formation of perceptual categories may be affected by exposure to two languages in which the phonemic status of phonetic segments differs. In the current study, electrophysiological measures (mismatched negativity—MMN) and behavioral measures (AX discrimination and identification) were employed to examine perception of a nine-step continuum resynthesized from natural tokens. Preliminary results indicate that early bilinguals show somewhat more categorical perception than monolinguals (i.e., sharper identification boundaries) of the nine-step continuum. MMN results, obtained during a task in which subjects were not attending to the auditory input, show clear MMNs for monolinguals for both cross- and within-category pairs. To date, results for early bilinguals show less clear indication of preattentive discrimination. The role of language experience and the relationship between the behavioral performance and the electrophysiological measures will be discussed.