There was a discussion last autumn on Jamie Berke’s Deafness Blog about whether a deaf child can be bilingual in sign languages at the age of three. Jamie wasn’t sure, but the consensus was, not surprisingly, “If kids can learn two or more verbal languages, why not signed languages?”´
In the days when deaf people didn’t move outside their own communities very much, the need and opportunities for sign language bilingualism were few, but that has been changing. Now signers of different languages quite often come together, at conferences for instance. Just as Esperanto has been proposed as a solution to the conflicts of spoken-language multilingualism, so an auxiliary international sign language has arisen called International Sign or Gestuno, but it’s not yet widely known enough.
In Canada there are two sign languages: (a) a dialect of American Sign Language (ASL) used in English Canada, and (b) Quebec Sign Language (LSQ) used in French Canada. They aren’t mutually intelligible. One discussant on the Deafness Blog wrote,
There are people who code switch depending on who they are with, and I have seen multilingual people alternate Quebec French sign (LSQ) and ASL with ease.Yes, so have I, though it‘s not common. But “people” here refers, I presume, to adults. How about young children?
The same discussant wrote,
Deaf children have been observed to jabber away among schoolmates in a child slang sign language, and use more formal sign in the classroom.That covers what the linguists call diglossia - speaking in different registers of the same language. But how about true bilingualism between different languages?
A striking empirical answer to the question is provided by the case of Jeremy (see photo), a Montreal child about whom there was a programme on Canadian TV in 2001. Both he and his parents were deaf. His mother was communicating with him in LSQ, his father in ASL. He had therefore learned both languages simultaneously as first languages.
Nobody in the blog discussion raised the question of translation. Perhaps because there are two kinds, or 'modes', of sign language interpreting. The first mode is not between two sign languages but between a sign language and a voice language. It’s extremely common and is done even by children in families where there are deaf and hearing members - a kind of language brokering - so its possibility is beyond question. Most of the Expert and Professional sign language interpreters are drawn from this pool of early bilinguals. The kind of bilingualism it assumes is called bimodal. The other kind, between two sign languages, is much rarer because there are fewer opportunities and motivations for it. The Natural Translation Hypothesis, which applies to sign language as much as to voice language, predicts that it exists in children like Jeremy. But so far I haven’t seen the evidence.
Jamie Berke, Can a deaf child learn multiple sign languages? Deafness Blog, 2009, http://deafness.about.com/b/2009/08/13/can-a-deaf-child-learn-multiple-sign-languages.htm#gB3
There’s a Wikipedia article on "International Sign".
Langues des signes. Anne Fleischman, reporter; Hélène Naud, producer. Radio-Canada, 2001. http://www.radio-canada.ca/tv/decouverte/reportage/langue_signes.html#
Babies and Sign Language website.