Slide Slam I4
Spanish-English Bilinguals' Phonetic Perception in Speech-Shaped Noise
Zunaira J. Iqbal1, Antoine J. Shahin1, Kristina C. Backer1; 1University of California, Merced
INTRODUCTION. Real-world listening situations are often noisy, and speech comprehension in these acoustically adverse situations is challenging, especially for bilingual listeners communicating in their second language (L2). Indeed, prior studies have demonstrated that compared to monolinguals, bilinguals have less accurate speech recognition when listening to their L2 in the presence of background noise (e.g., Mayo et al., 1997; Garcia Lecumberri & Cooke, 2006). Here we investigated how the presence of background noise influences Spanish-English bilinguals’ percepts along a /va/-/ba/ continuum, compared to English monolinguals. The phonemes /v/ and /b/ were selected to capitalize on the fact that Spanish phonology maps /v/ onto /b/, whereas English makes a clear distinction between these two phonemes. Another goal of this study was to examine whether bilinguals’ age of English acquisition plays a role in their perception along the /va/-/ba/ continuum. METHODS. The continuum from /va/ to /ba/ comprised five consonant vowel (CV) stimuli. On each trial, one CV stimulus was presented in Quiet or was embedded in speech-shaped noise at one of three signal-to-noise ratios (SNRs): +6 dB, 0 dB, and -6 dB. Spanish-English bilingual (n=36) and English monolingual (n=13) participants reported whether they perceived /ba/ or /va/ on each trial. Since Spanish phonology maps /v/ on /b/, we hypothesized that Spanish-English bilinguals would perceive /ba/ more often—especially towards the /va/ end of the /va/-/ba/ continuum and in noisier conditions—than English monolinguals. We also hypothesized that bilingual participants with a later age of English acquisition would perceive the stimuli as /ba/ more often, especially in noise, than the bilinguals with an earlier age of English acquisition. RESULTS. Overall, across both monolingual and bilingual groups, the SNR condition and the CV stimulus step (i.e., along the /va/-/ba/ continuum) significantly affected perception (both effects: p<0.001). There was also a significant interaction between the SNR condition and CV stimulus step (p<0.001). Overall, participants perceived /va/ significantly more often than /ba/ in the Quiet condition than in the other three noise conditions, with no differences observed during the three noise conditions. Furthermore, collapsing across the SNR conditions, participants perceived /ba/ more often as the continuum progressed from /va/ towards /ba/. Surprisingly, the bilinguals perceived /va/ significantly more often overall (mean=54%) than the monolinguals (mean=44%; p=0.006). This group difference was evident even in the Quiet condition, especially when participants listened to CVs towards the /ba/ side of the continuum. No interactions between group and SNR condition were observed, suggesting that SNR did not modulate this group difference. Finally, age of English acquisition did not drive these group differences, as there were no significant differences in perception between early and late sequential bilinguals (who learned English before and after age 5 years, respectively). CONCLUSION. These results suggest that the presence of the English-specific phoneme /v/ in the current task may have resulted in a phonetic recalibration process, whereby bilinguals’ perceptual phonetic boundaries can dynamically shift depending on language context. Follow-up experiments will further explore this phonetic recalibration process and its underlying neural mechanisms in Spanish-English bilingual listeners.