Editing Sign language (section)

=== Acquisition ===
{{See also|Language acquisition}}

Children who are exposed to a sign language from birth will acquire it, just as hearing children acquire their native spoken language.<ref>{{cite book|last=Emmorey|first=Karen|title=Language, Cognition, and the Brain|year=2002|publisher=Lawrence Erlbaum Associates|location=Mahwah, NJ}}</ref> In a study done at McGill University, they found that American Sign Language users who acquired the language natively (from birth) performed better when asked to copy videos of ASL sentences than ASL users who acquired the language later in life. They also found that there are differences in the grammatical morphology of ASL sentences between the two groups, all suggesting that there is a very important critical period in learning signed languages.<ref>{{Cite web|url=http://www.acfos.org/publication/ourarticles/pdf/acfos1/mayberry.pdf|title=The Critical Period for Language Acquisition and The Deaf Child's Language Comprehension: A Psycholinguistic Approach|last=Mayberry|first=Rachel|website=ACFOS|url-status=live|archive-url=https://web.archive.org/web/20171201072124/http://www.acfos.org/publication/ourarticles/pdf/acfos1/mayberry.pdf|archive-date=2017-12-01}}</ref>

The acquisition of non-manual features follows an interesting pattern: When a word that always has a particular non-manual feature associated with it (such as a [[Wh question|wh-question]] word) is learned, the non-manual aspects are attached to the word but do not have the flexibility associated with adult use. At a certain point, the non-manual features are dropped and the word is produced with no facial expression. After a few months, the non-manuals reappear, this time being used the way adult signers would use them.<ref>{{cite book|title=Advances in the Sign Language Development of Deaf Children|year=2005|publisher=Oxford University Press|location=Cary, NC|isbn=978-0-19-803996-9|pages=262–290|author=Reilly, Judy|editor1=Brenda Schick |editor2=Marc Marschack |editor3=Patricia Elizabeth Spencer |chapter=How Faces Come to Serve Grammar: The Development of Nonmanual Morphology in American Sign Language}}</ref>