Assessing the scope of expertise-driven advantages in bimodal and unimodal bilinguals: A comparison of signed and spoken language interpreters

Evidence from research on bilingualism has prompted the ‘bilingual advantage hypothesis’, positing that language control is needed when two languages are processed and such a control during bilingual processing enhances cognitive functioning. However, investigations have shown that, compared with bilinguals who are fluent in two spoken languages (unimodal bilinguals), those who use a signed language and a spoken language (sign-speech or bimodal bilinguals) do not seem to show a bilingual advantage (Emmorey, Luk, et al., 2008). It is assumed that the different language modalities (one signed and one spoken) in bimodal bilinguals allow simultaneous production of two languages and reduce the demands for language control because the two languages do not compete for the same articulatory output system (Emmorey, et al., 2016). Past studies often involve participants whose bilingual competency and experience are too diverse, making a comparison among studies difficult. Comparing bimodal and unimodal interpreters, highly advanced bilinguals who practice switching between two languages as a profession, can provide a window into whether bilingual advantage is modality specific. This study (the Bimodal Study) is an extension of an ongoing GRF supported study, “Assessing the scope of expertise-driven advantages in bilinguals: A comparison of interpreters and translators” (the Unimodal Study), where we gauge participants’ cognitive functioning in unimodal (speech-speech) interpreters, translators, interpreting students, and non-interpreter unimodal bilinguals to see if long-term engagement in an extreme bilingual activity such as simultaneous interpreting has significant consequences on cognitive abilities. The participants in this proposed Bimodal Study will be bimodal professional interpreters, students who receive interpreting training, and an age-matched control group composed of non-interpreter bimodal bilinguals, including students. The data from both groups of students will be collected three times throughout the two years when they receive their respective training. The data from professional interpreters and non-interpreter bilinguals will be collected one time and their performance in the various cognitive tests will be compared with students’ performance in the same tests. The same set of validated tests adopted for the Unimodal Study will be used in the Bimodal Study. We will compare the results from both studies to see if language modality is a differentiating factor for any observed effects, and if yes, how task demands associated with different modalities are manifested in the impacts on cognitive functions. Our unique approach to comparing two groups of bilinguals with different language modalities can shed light on the adaptive capacity of bilingual cognitive systems.