As found in all human languages (both signed and spoken) observed by linguists, language naturally changes over time and geography. It also varies from person to person, across regions, and situations.
Sociolinguistics is the study of the relationship between language and society. In sociolinguistics, 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 different types of variation: phonological, regional, gender-related, and few other types. This post focuses on the particular language, American Sign Language (ASL).
This common type of variation is that a few signs of the same language (ASL) are different across regions in North America; nevertheless, ASL speakers still understand one another. E.g. "supper" and "dinner" in English. "Flat" in British English for "apartment" in American English and "tube" for "television" respectively).
In ASL, a sign for "test" is different in British Columbia (Vancouver areas) from the rest of the provinces and the states in North America. The sign for "Halloween" and "pizza" have more variants than other signed words.
A difference in the form of a ASL word (that is not incorrectly pronounced) is due to phonological variation but not due to regional variation. For example, there are two phonological variants of the signed word SURGERY. This handshape-based difference is the pinkie: "A" and "Y".
"surgery" in ASL with the pinky closed.
"surgery" in ASL with the pinky open.
This difference is an analogue to the difference in a spoken language, such as "color" in American English and "colour" in Canadian English. But again, this sign "surgery" is not due to the regional variation. The sign of this phonological variation is not found in regional variation but in individuals within the same regional community.
A sign may be phonologically variable in register variation. The sign KNOW, for example, is on the higher part of the head in formal citation yet it is often used on the lower part of the head in informal situation. Another phonological variation is the accents.
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 there were segregated Deaf schools in the past in the U.S.
Language changes across generations. Some forms of the language in ASL vary between the older and the newer generations of ASL speakers.
Contextual variation is how an ASL speaker uses different forms for the same meaning or concept in a formal lecture and in an everyday settings.
Though there is little study on sex/gender variation, female and male signers use different forms of a sign.
Like other languages, historical change and sociolinguistic variation exist in American Sign Language as well as other signed languages.