It has been demonstrated that, in addition to language acquisition being possible younger (when mouths are perhaps not yet nimble enough to annunciate), signed languages reside in a different portion of the brain, meaning that often brain damage patients -- stroke, trauma, etc. -- keep a signed language despite losing a spoken one.
(by "signed language", I do not intend a fingerspelling of another spoken language, or a small set of gestures such as baseball signs, but a whole language.)
Discussion (2)
Although I don't.
Yes, the advantage of not losing language entirely is huge. But you should have a signed language and a spoken language in an ideal world, because the idea is to not put all your eggs in one basket.
Plus, I think if ASL were taught to basically everyone, it would make being deaf such an incredibly much smaller issue. It would simply eliminate a whole host of problems.
of course, it'd also cause merry havoc with Deaf culture. But I still think it'd be best in the long run.