I was going to post this as a reply in the "
You know you're a language nerd when..." thread, but thought it better placed here due to its unexpected length and...well...specifically sign language related nerdiness.
Cainntear wrote:vogeltje wrote:Teango wrote:When you read "Sign in to Goodreads to Learn More" and your hands automatically move to sign
good read [+pl. classifier]...
I met a deaf girl yesterday and I thought of you and that you'd talk in sign langauge with her, although I don't know if she knows it. I don't think that all deaf people know sign language. She can speak spoken English, but you can notice that she's deaf when she speaks. I would love to learn sign language.
Teango speaks New Zealand Sign Language, not British Sign Language.
As part of the same BANZSL language family, NZSL, Auslan, and BSL are pretty much kissing cousins. As far as I know, NZSL is based on a much earlier form of BSL (which is now quite distinct from modern BSL and its variations), but it has also been influenced by Auslan, Irish Sign Language, and Māori, as well as ASL more recently and to a lesser but increasing extent (which like Irish Sign Language, is part of the French Sign Language family and more distantly related).
I'm not sure how accurate the data is on Wikipedia regarding lexical similarity between BSL and NZSL, but both the BSL and NZSL entries on Wikipedia cite the same source as McKee & Kennedy (2000). The
BSL entry claims that "Auslan, BSL and NZSL have 82% of signs identical (using concepts from a Swadesh list). When considering similar or related signs as well as identical, they are 98% cognate.", whereas the
NZSL entry claims that "There are 62.5% similarities found in British Sign Language and NZSL, compared with 33% of NZSL signs found in American Sign Language."
A quick glance over at the Discussion section of the cited article reveals that the results largely depend upon which set of words were used for testing similarity:
As we noted, on lexicostatistical grounds (Crowley, 1992), 36% to 81% commonality of signs in two languages suggests that the languages belong to the same family. Above 81%, they are dialects of the same language. It is clear, therefore, that the evidence relating to Swadesh's core concepts summarized in Table 5.3 shows that the three varieties - Auslan, BSL, and NZSL - are dialects of the same language. On grounds of mutual intelligibility, the anecdotal evidence from the Deaf community also supports this position. However, using the randomly selected NZSL signs as the basis for comparison, the three sign languages are shown to have less in common. On the evidence of the analysis of randomly selected NZSL signs, we are obliged to suggest that the speech varieties share between 62.5% and 66% of their lexicon and that some significant divergence has occurred within the family of languages.
Johnston (2003) also suggests that "Auslan, BSL and NZSL should be considered as varieties or dialects of the same sign language, with an even higher degree of mutual intelligibility and lexical overlap than hitherto assumed". Unfortunately, I wasn't able to get a hold of this article, but would be interested in looking over the data sometime and getting some numbers on this.
From my own limited experience with BSL and NZSL, I've noticed considerable overlap in signs and syntax, and am delighted with the thought of these two languages (oh, and let's not forget Auslan too) being mutually intelligible (3 for the price of 1.x!) I am very reluctant, however, to accept that NZSL and BSL are simply dialects of the same language and would need to research this further. I believe there's so much more to comparing languages than simple lexicostatistical analyses (and with only one out of a half a dozen different Swadesh lists at that), and the results when using randomly chosen signs in McKee & Kennedy's (2000) study falls well below the criteria set out by Crowley (1992) for designating them as dialects.
TLDR; New Zealand, Australian, and British Sign Language may be closely related, but I've yet to be convinced they're dialects of the same language. More research is required.