Linguistics of Sign:
In linguistic terms, sign languages are as rich and complex as any oral language, despite the common misconception that they are not “real languages”. Professional linguists have studied many sign languages and found them to have every linguistic component required to be classed as true languages.
Sign languages are not pantomime – in other words, signs are largely arbitrary and have no necessary visual relationship to their referent, much as most spoken language is not onomatopoeic. Nor are they a visual rendition of an oral language. They have complex grammars of their own, and can be used to discuss any topic, from the simple and concrete to the lofty and abstract.
Cognitive development in deaf children: the interface of language and perception in neuropsychology