Early versus Extended Exposure in Speech and Vocabulary Learning: Evidence from Switched-dominance Bilinguals

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Both the timing (i.e., ‘when’) and amount (i.e., ‘how much’) of language exposure have been shown to affect language-learning outcomes. Monolinguals and (most) bilinguals confound these two factors of early exposure and extended exposure (i.e., their first-acquired language is their most used or dominant language), making it difficult to isolate the benefits that either one of these exposure patterns could provide independently for language acquisition. Switched-dominance bilinguals (i.e., heritage speakers) dissociate early and extended exposure as their first-acquired language (L1) is considerably weaker (non-dominant) compared to their stronger (dominant) second-acquired language (L2). This dissociation allows us to examine the unique benefits of both early and extended exposure on language acquisition. The current study focuses on how these exposure patterns affect speech and vocabulary learning in heritage speakers (L2-dominant) in three separate experimental paradigms. In Experiment 1, Spanish heritage speakers (SHS) recorded sentences in Spanish (their non-dominant L1) and English (their dominant L2) along with L1-dominant Spanish and English controls in their respective (dominant) L1s. These sentences, embedded in noise at two signal-to-noise ratios (-4 dB and -8 dB signal-to-noise ratio; SNR), were presented aurally to L1-dominant listeners of Spanish and English, respectively. At the easier SNR (-4 dB SNR), SHS showed no differences in intelligibility across languages with both their English and Spanish scores reaching L1-dominant control levels of speech intelligibility. At the harder SNR (-8 dB SNR), SHS English intelligibility matched that of English L1-dominant controls, yet SHS Spanish intelligibility was significantly lower compared to that of Spanish L1 controls. In Experiments 2 and 3, Spanish heritage speakers (SHS, L2-dominant English) performed a lexical decision task (Experiment 2) and single-word reading task (Experiment 3) in both English and Spanish along with L1-dominant English and Spanish controls, respectively. The stimuli of interest varied orthogonally on age of acquisition (AoA) and lexical frequency, two factors known to affect word retrieval. In their dominant L2 English, SHS received similar benefits (i.e., faster reaction times and/or shorter word durations) of early-acquired and high frequency words compared to L1-dominant English controls and were not more adversely affected (i.e., slower reaction times and/or longer word durations) on late-acquired or low frequency words in English. In their non-dominant L1 Spanish, SHS were slower to respond to words over all (Experiments 2 and 3) and produced longer word durations (Experiment 3) compared to L1-dominant Spanish Controls. SHS were also more adversely affected (i.e., slower reaction times in Experiment 2 and 3; longer word durations in Experiment 3) by late-acquired and low frequency Spanish words compared to L1-dominant Spanish controls. Combined, these results suggest that the benefits of early exposure to language may be limited in some areas of speech and vocabulary processing and that extended language usage, resulting in language dominance, may be sufficient to overcome any processing difficulties incurred in the initial delay to the L2. Furthermore, these data challenge what is meant by the term “native speaker” when modeling bilingualism on an L1-L2 distinction, as such a dimension may be unable to accurately predict the linguistic performance of some bilingual speakers.

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  • 02/25/2019
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