Bimodal Bilinguals, those who are fluent in both spoken language, exhibit unique behaviors since they access two separate sensory motor systems for comprehension and production
Being bilingual is becoming more and more of a necessity in this day and age. Not only does it open doors to more job and social opportunities in the world, it ultimately allows one to expand the way he or she thinks. Knowing this, much research has been done on unimodal bilinguals, that is, those who are bilingual in two spoken languages. However, not much research has been done on bimodal speakers, those who are fluent in spoken language and sign language. The goal of Emmorey, Giezen, and Gollan is to do a literature review of all the research done on bimodal bilinguals. These people offer a unique window into the processing of language as they use two distinct sensory-motor systems to comprehend and produce language.
Investigations in language mixing show that bimodal bilinguals have a strong preference for code-blending over code-switching according to multiple studies. Furthermore, this shows a preference for syntactically congruent sentences. To put it simply, rather than switching from a spoken language to a signed language (or vice versa) midway through their sentence, speakers would rather make up a grammatical morpheme in sign that fit their sentence in the spoken language. Below are examples of some ways in which code-blending was done in the place of code-switching. The signs are written in capitals in English glosses (the nearest translation equivalent; hyphens indicate a multi-word gloss), and brackets indicate the co-occurring speech.
By implication, this shows that it is most likely less costly to retrieve that dual lexical retrieval is less costly than language inhibition, which is assumed to be required for code-switching. Let us take Legos as an example. If I have a box full of Legos, and I only want to take out the green Legos, I can do so. However, since there are so many Legos in the box, there is a good chance that one of the green Legos will be stuck to another Lego of a different color. What this research is saying that when these Legos are stuck, it is more efficient to just use the green Lego with the other Lego that it is stuck to.
Although dual retrieval is more efficient, is it cost-free? Emmorey et al. tested subjects by asking them to name pictures in English alone, ASL alone, and then in both ASL and English (code-blend). Results showed that participants actually retrieved words faster for ASL when it was code-blended with English compared to just retrieving the target word in ASL. However, participants were slower in retrieving English words when code-blended with ASL. This suggests that code-blend production does not incur a lexical processing cost despite the fact that two lexical items must be retrieved simultaneously.
One aspect of this study that Emmorey et al. are calling for is studying the impact of mouthing when it comes to signing. We have already seen how links between languages at the lexical or semantic level and that perceptual overlap is not required for language co-activation. However, if mouthings are part of a lexical representation of a sign then there is a possibility that the phonological link between the mouthing and sign may play a part in lexical retrieval. However, at this point, no research has been done on this topic.
When looking at which areas of the brain are working in bimodal bilinguals, their brains differ from unimodal bilinguals due to differences in the convergence of neural networks that control their two languages, with more sensory-motor overlap for unimodal bilinguals. What is fascinating about this subject is that the two languages do not compete for the same articulatory output system and perceptual cues to language membership. This gives us an insight to how bimodal bilingual speakers are able to stores lexicons different from unimodal bilingual speakers. We can begin to see that pulling out blocks of Legos may indeed be more efficient than trying to take apart the Lego pieces you want.
Emmorey, Karen, Marcel R Giezen, and Tamar H Gollan. “Psycholinguistic, Cognitive, and Neural Implications of Bimodal Bilingualism.” Bilingualism (Cambridge, England). U.S. National Library of Medicine, March 2016. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5553278/.