Language naturally changes over time and geography as found in all human languages (both signed and spoken) observed by linguists.
In sociolinguistics (the study of the relationship between language and society), linguists study interaction between linguistic and social variables and how language is used in various settings and situations. One of the areas in sociolinguistics that linguists study is variation in language.
Variation is commonly defined as "a different way of saying the same thing" (e.g. "pop", "soft drink", and "soda" for the same thing or meaning).
There are some types of variation: phonological, regional, gender-related, and few other types. This post focuses on the particular language, American Sign Language (ASL).
ASL is used across North America long since the old days when the first deaf schools popped up all over North America, starting from the first permanent school for the deaf (1817) in Hartford, Connecticut. First, the language grew and spreaded through deaf schools, Deaf teachers and students, Deaf families, and Deaf communities across North America. Added, Gallaudet University where students from all over North America attended and came back home with ASL variations and deaf travelers. Then added, the Internet where Deaf signers exchanged in one big place.
Sometimes, a sign was thought to be from a region in Canada also turned up to be also from another region in the U.S. Variation between California and New York or Alberta and Ontario is no more difference than between the U.S. and Canada or Alberta and Minnesota, for example. That is to say, there are variations across North America.
It's not unusual to see variations on the Internet, yet native signers can still understand one another, as the core of ASL is basically the same, just like hearing Americans, Canadians and Britishs are able to converse with one another without any barriers (e.g. "tube" and "television" or "flat" and "apartment".
A common type of variation is the regional variation which a few signs are various across the regions. A few ASL signs have larger number of variants such as PIZZA and HALLOWEEN than other signed words. Some ASL signs are particularly local that are different from the rest of the regions. Some variations are common in large regions that native signers are accustomed to.
Phonological variation is a variation in the form of pronunciation. For example, there are two phonological variants of the signed word SURGERY based on the handshape difference -- one with the pinkie ("Y" handshape) and the other with no pinkie ("A" handshape). Another example is RABBIT -- one with the "H" handshape and the other with the "13" handshape.
"surgery" in ASL with the pinky closed.
"surgery" in ASL with the pinky open.
This difference is an analogy to the variation of the word "color" in American English and "colour" in Canadian English. But again, this sign "surgery" is not due to the regional variation but due to the phonological variation, whereas English words "color" and "colour" are due to the regional variation. Phonological variation is not necessarily found in regional variation but in individuals within the same regional community.
Native signers can naturally recognize whether a sign is a phonological variation or a mispronunciation. Some signs of phonological variation are acceptable while others with differnet phonetic structure of signs are recognized as mispronunciation.
Another variation may be due to a register (formal/informal continuum). The sign KNOW, for example, is on the higher part of the head in formal citation yet it is sometimes used on the lower part of the head in informal situation.
Some two-handed signs in formal register are signed one-handed in informal setting. E.g. two-handed HORSE vs one-handed HORSE.
Ethnic variation can be derived from different backgrounds of Deaf ASL-speaking people. For example, there are some variations of the signs between Black Deaf and white Deaf signers where schools for the Black Deaf were segregated in the U.S. in the past.
It's also true with some Deaf immigrants. Many assimilated or acculturated Deaf families speak ASL with a few signs from their native signed languages at home, often because a few signs of the native (signed) languages have specific meanings that are not found in ASL.
Language naturally changes across generations. Some forms of the language in ASL vary between the older and the newer generations of ASL speakers. E.g. WILL in 1913 vs WILL today, JEALOUS in 1913 vs JEALOUS today.
Contextual variation is how an ASL speaker uses different signs for the similar meaning or concept in contexts.
Gender/sex variation is how female and male signers use subtle forms of a sign. E.g. some signs on the chest tend to be signed a little higher on the chest in female signers than that in male signers.
And, accent (which often surprises ASL students). Yes, there is an accent in sign language. Often native signers and dodas (Deaf of Deaf families) can tell whether signers and long-time interpreters are hearing or not. They are sensitive to the subtle differences in accent.
Scenario: A native Deaf signer, who is also a ASL teacher and interpreter, taught hearing students in an ASL course at a post-secondary institution. Next term, one of the students learned a different sign for a word from a hearing teacher and asked for clarification. The hearing teacher told the student that the sign from the Deaf teacher was incorrect. [audism] Fortunately, the student checked with the Deaf teacher who later summoned a face-to-face meeting with the hearing colleague via email. The hearing teacher replied with an apology via email to avoid the meeting.
Do: Learn from Deaf ASL teachers, native Deaf signers (both Deaf of Deaf families and Deaf people growing up in Deaf schools), and some culturally Deaf signers. Whether they use variations, accept them but still check with other native Deaf signers to learn more contexts.
Keep in mind that Deaf native signers are the living carriers of full-fledged sign language from generation to generation as they use them all their lives.
Scenario: A hearing student took an ASL course with a Deaf instructor and then took another ASL course with another Deaf instructor. Occasionally, the hearing student would notice a variant of the sign or a different sign between two Deaf teachers and asked the teacher about it.
Do: Ask both Deaf teachers and learn more; perhaps ask "How does this sign mean different from that [sign]?" Or, "How is this sign used compared to that sign?". The more you learn ASL, the more you learn various contexts.
It could be one of some variations (e.g. generational) or maybe not -- Beyond variations, it could be a grammar! It may be a verb inflection. It may be an adjective in compound with the noun or verb. It may be an adverb in compound with the verb. It may be a synonym.