The Effect of Bilingual Proficiency in Indian English on Bilabial Plosive

Background: Bilingual speech production studies have highlighted that level of proficiency influences the acoustic-phonetic representation of phonemes in both languages (MacKay, Flege, Piske, & Schirru 2001;Zarate-Sandez, 2015). The results for bilingual speech production reveals that proficient/early bilinguals produce distinct acoustic properties for the same phoneme in each language, whereas less proficient/late bilinguals produce acoustic properties for a phoneme that is closer to the native language (Flege et al., 2003;Fowler et al., 2008). Acoustic-phonetic studies for Hindi (L1) and Indian English (L2) for bilingual speakers have been understudied, and the level of proficiency has not been considered in Hindi and Indian English bilingual speakers. The present study aimed to measure the acoustic differences produced by bilingual speakers of varying proficiencies for Indian English on bilabial plosive and determine how the bilabial plosives are different from American English bilabial plosives.Methods: The sample size for this study was twenty-four. However, only twenty participants (eleven females) between the ages of eighteen and fifty, with normal speech and hearing, were recruited. The lack of recruitment of four more participant was due to the inability to find bilingual speakers who spoke Hindi as their first language and Indian English as their second language and COVID-19 restrictions imposed on recruitment (n=4). The participants were divided into three groups based on language and proficiency: a monolingual American English group, a proficient bilingual Hindi-Indian English group, and a less-proficient bilingual Hindi-Indian English group. The bilinguals were divided into a proficient and less proficient group based on the Language Experience and Proficiency Questionnaire (Marian, Blumenfeld, & Kaushanskaya, 2007). Following the screening, participants took part in a Nonword Repetition Task. Data were analyzed using Praat and Voice Sauce software. A linear mixed-effects model using R statistics was used for the statistical analysis.Results: Data from 20 participants (seven proficient bilingual speakers, five less-proficient bilingual speakers, and eight monolingual speakers) were included in the data analysis. Approximately four thousand repetitions were evaluated across the remaining participants. There were no significant main effects across the four dependent variables, but there was an interaction effect between group and phoneme on two dependent variables. The closure duration for proficient bilingual speakers compared to less-proficient bilingual speakers were significantly different between the voiceless unaspirated bilabial plosive (VLE) and voiceless aspirated bilabial plosive (VLH), as well as voiced unaspirated bilabial plosive (VE) and voiced aspirated bilabial plosive (VH). For spectral tilt, there was a significant difference between the VLE and VLH for proficient bilingual speakers compared to less proficient bilingual speakers.Discussion: The results of this study suggest that proficient bilingual speakers have faster rate of speech in both their first and second language. Therefore, it is difficult to provide information on whether this group has separate acoustic-phonetic characteristics for each phoneme for each language. In contrast, the less-proficient bilingual speakers seem to have a unidirectional relationship (i.e., first language influences the second language). Furthermore, the results of the acoustic characteristics for the control group i.e., monolingual American English speakers suggest that they may have acoustic-phonetic characteristics that represent a single acoustic-phonetic representation of bilabial plosive with their voicing contrast. (PsycInfo Database Record (c) 2022 APA, all rights reserved)