Doctoral Dissertation Research: Speech perception in bilingual and monolingual speakers under normal and adverse listening conditions

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The ability of listeners to identify words and speech sounds in sub-optimal listening conditions is a remarkable adaptation to the everyday use of language, and in order to understand this capacity fully it is necessary to clarify the role of prior linguistic experience in shaping this ability. Recent research suggests that whether a listener is a monolingual or bilingual speaker of the target languages plays an important role in shaping this ability. Under the direction of Dr. Aline Godfroid, Mr. Jens Schmidtke will investigate speech perception in noise (SPIN) in bilingual speakers for his dissertation research. While noisy environments generally make understanding speech more difficult, noise seems to put an extra burden on bilingual speakers. Results from many studies suggest that monolinguals and early bilinguals tested in their dominant language perform the same under quiet conditions; however, bilinguals suffer more from adverse listening conditions than monolinguals. Though this finding is quite robust, relatively little is known about the cognitive demands of bilingual SPIN and how noise affects bilingual speech perception in real time.In the first part of this study the researchers will investigate individual differences in bottom-up (phoneme perception) and top-down (executive functions) processes that contribute to SPIN in monolingual and early bilingual listeners. To this end, participants will complete a test of SPIN and results from various tests (vocabulary knowledge, working memory, auditory attention, and phoneme discrimination ability) will be used to predict SPIN performance. The prediction is that bilingual speakers will rely more on top-down processes to compensate for weaker processing of bottom-up information. In the second part of the study, the researchers will investigate SPIN in real time by recording listeners' eye movements. In the visual-world eye-tracking paradigm, participants see pictures of objects on a screen while they hear instructions to click on one of the pictures. Given that eye movements to pictures are closely linked to ongoing language processing, results will show how noise affects speech perception in the moment. The researchers predict that, in bilinguals, noise will result in greater distraction by pictures with similar sounding referents and thus slower word recognition compared to monolinguals.Results from these experiments may help us better understand the bilingual disadvantage for SPIN. Results may also deepen our understanding of how factors other than hearing acuity contribute to bilinguals' ability to hear in noise and thus be of value to a wide range of researchers and practitioners.