Behavioral and electrophysiological correlates of vowel perception in monolingual and simultaneous bilingual users of Canadian English and Canadian French

In this dissertation, the phonetic perception abilities of simultaneous bilingual (SB) language users exposed to both Canadian English (CE) and French (CF) from birth were tested to examine mechanisms underlying this process. It is well established that monolingual speakers' speech perception abilities are highly tuned to the sounds of their native language, and that this language specificity affects how they distinguish the sounds of a second language. However, it is not well understood how the speech perception skills of simultaneous bilinguals, who are native speakers of two languages, are shaped. In order to investigate speech processing in this population, two studies were designed to assess the vowel perception abilities of monolingual and SB users of CE and CF at two different stages of speech processing.;In Study 2, using event-related brain potentials, we recorded pre-attentive processing involved in vowel perception as reflected by the mismatch negativity (MMN). The SB listeners exhibited a MMN pattern that was distinct from both monolingual listener groups even during the earliest levels of speech processing, as the SB pre-attentive system is tuned to access sub-phonemic detail with respect to both of their input languages, including detail that is not readily accessed by either set of monolingual peers. This automatic access to fine phonetic detail may be essential in supporting the SBs' ability to make rapid, effortless shifts in perception across different communication contexts (French, English, bilingual).;In Study 1, using a behavioral vowel categorization paradigm, we measured how the control of active language mode or language context (English, French, or bilingual) affects the perception of acoustically similar cross-language vowel categories (specifically, front /y/ and back /u/ high vowels). As expected, monolingual speakers demonstrated a language-specific perceptual pattern for the vowels; however, the SB participants displayed different patterns in each active language mode and were able to accommodate acoustically similar vowel categories relevant in the target language, which was achieved by dissimilation (separation) of the categories. These findings indicate that SB listeners rely on a finely detailed perceptual space and are flexible as they adapt their perception to different language environments.