Bimodal bilingualism refers to the ability to use at least one oral language and at least one sign language, which utilize two different modalities. An oral language consists of a vocal-aural modality versus a signed language which consists of a visual-spatial modality. Bimodal bilingualism can arise from several circumstances such as hearing children raised in Deaf families, Deaf individuals who use sign as their primary language and then also learn a spoken or written language, or they are exposed to both modalities through family, education, or community. Because speech and sign utilize different modality systems, bimodal bilinguals are able to produce and perceive a spoken and a signed language simultaneously compared to those who are unimodal. Unimodal bilinguals are only able to perceive a spoken language at a given time. Research on bimodal bilingualism focuses on how the two languages are acquired, how they interact cognitively and how individuals manage both languages in communication. Topics commonly discussed include developmental neural pathways for Deaf and hearing Children of Deaf Adults (CODAs), patterns of code-blending and code-switching, sociolinguistic experiences within the Deaf community, and cross-modal influences on grammatical structure.
Also addressed below: the range of language proficiencies among bimodal bilinguals, current perspectives in neurolinguistics, common misconceptions about bimodal bilingualism, and ongoing debates about terminology, educational policies, and language access.
In discussions of multilingualism in the United States, bimodal bilingualism and bimodal bilinguals have often not been mentioned or even considered. However, bimodal bilinguals share many of the same traits as other bilinguals (those with competency in at least two spoken languages), as well as differing in some interesting ways, due to the unique characteristics of the Deaf community. Bimodal bilinguals also experience neurological benefits similar to those that unimodal bilinguals do (see Cognitive effects of bilingualism).
History and cultural background American Sign Language, the predominant sign language used in the U.S., only began to be acknowledged as a natural language in the 1960s (in discussions of bimodal bilingualism in the U.S., the two languages involved are generally ASL and English).
Deaf Culture is vital to understanding this concept of bimodal bilinguals. A substantial number of bimodal bilinguals are Children of Deaf Adults (CODA) or other hearing people who learn sign language for various reasons. Deaf people as a group have their own sign language(s) and culture that is referred to as Deaf, but invariably live within a larger hearing culture with its own oral language. Thus, "most deaf people are bilingual to some extent in [an oral] language in some form".
Since linguists did not recognize ASL as a true language until the second half of the twentieth century, there has been very little acknowledgment of, or attention or study devoted to, the bilingual status of the American Deaf community. Deaf people are often "still seen by many as monolingual in the majority language whereas in fact many are bilingual in that language and in sign".
Unlikelihood of large-scale language shift Language shift "occurs when speakers in a community give up speaking their language and take up the use of another in its place". ASL in particular, and sign languages in general, are undeniably influenced by their close contact with English or other oral languages, as evidenced by phenomena such as "loan signs" or lexicalized fingerspelling (the sign language equivalent of loanwords), and through the influence of contact sign. However, due to the physical fact of deafness or hearing loss, deaf people generally cannot acquire and speak the majority language in the same way or with the same competency that the hearing population does. Simultaneously, Deaf people still often have a need or desire to learn some form of English in order to communicate with family members and the majority culture. Thus, Deaf communities and individuals, in contrast to many hearing bilingual communities and individuals, will tend to "remain bilingual throughout their lives and from generation to generation".
Acquisition
Simultaneous vs Sequential Acquisition Some bimodal bilinguals acquire both languages from an early age (a.k.a. simultaneous), while others learn one language fire and the other later on in life (sequential). This is dependent upon home language environment, educational language environment, and language access (regardless of sign or spoken language). It is not uncommon for sign language access to be delayed, limited, or no access altogether for many Deaf children especially Deaf children that are born into hearing families (which is the case 90% of the time). Because of this, there is much variability in language exposure as well as production.
Diverse Range of Language Competency To be defined as bilingual, an individual need not have perfect fluency or equal skill in both languages. Bimodal bilinguals, like oral-language bilinguals, exhibit a wide range of language competency in their first and second languages. Bimodal bilinguals show a range in their language skills. Some are highly proficient in both modalities, whereas others heavily rely on one language over the other. There are other factors at play here such as age and context of exposure, education experience, community support, and how frequently the individual uses that language. For Deaf people (the majority of bimodal bilinguals in the U.S.), level of competency in ASL and English may be influenced by factors such as degree of hearing loss, whether the individual is prelingually or post-lingually deaf, style of and language used in their education, and whether the individual comes from a hearing or Deaf family. Historically, assessment of bilingual children would only measure proficiency in one of their languages. In more recent research, linguists and educators have identified this design flaw. It can be concluded that most bilingual children achieve phonological, lexical, and grammatical milestones at the same rate as monolingual children. This same phenomenon has been found in comparing unimodal bilinguals and bimodal bilinguals. In a study by Fish & Morford (2012), bimodal bilingual CODAs have demonstrated the same rate of success in these areas as their unimodal bilingual peers.
Language proficiency among bimodal bilinguals varies widely. Factors influencing English comprehension include age of exposure, quality of language access, educational experiences, and individual differences in literacy development. Lipreading alone provides limited access to English phonology, as only some phonemes are visually distinguishable, but many Deaf individuals develop strong English literacy skills through multimodal exposure. Additionally, many Deaf bilinguals who have fluency in written English choose not to speak it because of the general social unacceptability of their voices, or because they are unable to monitor factors like pitch and volume. The simultaneous production of speech and sign is referred to as simultaneous-communication or sim-com.
Language use
Code-Switching Deaf or bimodal bilinguals, in their day-to-day lives, move among and between various points on the language mode continuum depending on the situation and the language competency and skills of those with whom they are interacting. For example, when conversing with a monolingual, all bilinguals will restrict themselves to the language of the individual with whom they are conversing. However, when interacting with another bilingual, all bilinguals can use a mixture of the two common languages. While early aged bimodal bilinguals have more than one mode to communicate a language, they are just as susceptible as unimodal bilinguals to confusing domains and using the "wrong" language in a given situation. Code-switching is a common phenomenon found among bilinguals; for bimodal bilinguals.
Code-Blending Another equivalent phenomenon is code-blending, which "involves simultaneous production of parts of an utterance in speech and sign." Examples of code-blending would be using ASL word order in a spoken English utterance, or conversing by showing an ASL classifier and speaking the English equivalent phrase simultaneously. Like unimodal bilinguals, bimodal bilinguals will activate, deactivate or adjust their use of each language according to their domain. For ASL-English bilingualism, "deaf students' vocabulary knowledge in each language will be related to the contexts where the two languages are used." That is, vocabulary and topics learned and discussed in ASL will be recognized and recalled in ASL, and "English vocabulary will reflect the contexts where English is accessible to deaf students."
Contact Signing Because almost all members of the American Deaf community are to some extent bilingual in ASL and English, it is rare that a Deaf person will find themselves conversing with a person who is monolingual in ASL. Therefore, unless an American Deaf person is communicating with someone who is monolingual in English (the majority language), he or she can expect to be conversing in a "bilingual language mode". The result of this prolonged bilingual contact and mixing between a sign language and an oral language is known as contact sign. Deaf children and their parents communicated using several modalities, such as oral-aural and visual-gestural. The mixed use of ASL and spoken English in bilinguals is discussed in this article, and led to contact signing. In the deaf community, contact signing is a common occurrence. The author covered many contact sign approaches in complex layers of ASL and spoken English expressions.
Contact signing refers to forms of communication that emerge when signers and non-native signers interact, resulting in features from a signed language and a spoken language appearing together. In the context of American Deaf communities, contact signing often occurs in interactions between ASL users and English-dominant individuals.
Contact varieties may include:
use of ASL lexicon but with English-influenced word order mouthing of English words while signing fingerspelling of English vocabulary reduction or simplification of ASL morphological features
These forms arise from language contact rather than representing a separate language, and they vary depending on participants’ proficiencies and communication goals (Lucas, C. & Valli, C. (1992). Language Contact in the American Deaf Community. Academic Press).
Neurological implications, effects, and benefits
Most modern neurological studies of bilingualism employ functional neuroimaging techniques to uncover the neurological underpinnings of multilingualism and how multilingualism is beneficial to the brain. Neuroimaging and other neurological studies have demonstrated in recent years that multilingualism has a significant impact on the human brain. The mechanisms required by bilinguals to code-switch (that is, alternate rapidly between multiple languages within a conversation), not only demonstrate increased connectivity and density of the neural network in multilinguals, but also appear to provide protection against damage due to age and age-related pathologies, such as Alzheimer's. Multilingualism, especially bimodal multilingualism, can help slow to process of cognitive decline in aging. It is thought that this is a result of the increased work load that the executive system, housed mostly in the frontal cortex, must assume in order to successfully control the use of multiple languages at once. This means that the cortex must be more finely tuned, which results in a "neural reserve" that then has neuroprotective benefits.