Sign Languages are Separate Languages
Sign language is a language that predominantly uses signs, facial expressions and hand gestures as opposed to acoustically conveyed sound patterns. While the manual communication system shares many similarities with languages; they are not just a signed form. They have their own vocabulary, syntax, grammar and sentence structure.
There are lots of different types of Sign Language
There are thought to be around 135 legal sign languages worldwide and over 6000 unofficial ones, with all of them having their own vocabulary with different signs. American Sign Language and British sign language are very different, with ASL actually taking most of its roots from French SL. In the photo above is the word for Maths in ASL and Japanese SL.
ASL is a widely spoken language
In the US, ASL is the third most spoken language after English and Spanish with roughly half a millions speakers.
Babies learn Sign Language the same way they learn normal languages
All languages, spoken or signed, are acquired in the same way from child birth. Hearing children of deaf parents will pick up both their native language and the sign language and will be bi-lingual from birth, this works the other way around too. Deaf babies babble in sign language before they grasp the entire language, instead of baby noises they make baby signs.
Brain damage affects Sign language the same way it affects spoken language
Troubles with communicating after an accident that causes brain damage or a stroke is uniform with all languages. Sign language speakers will muddle up words and lose sentence structure the same way speakers of a spoken language suffer.
We have witnessed a language at birth
Deaf children have created their own sign language.In Nicaragua in the 1970’s a group of deaf children created a sign language in the playground. After some time this language had vocabulary, grammar and structure. It is now called Nicaraguan Sign Language.