Is it possible for a person to acquire a written language as their native language?

Hello all the good people, Clarissa and Audrey and Brian. I was going to join in to your discussion under Brian’s answer, but it didn’t head in the direction I was hoping.

Laura Bridgman and Helen Keller, who are the deaf–blind people Brian alludes to, communicated through finger spelling, read Braille, and wrote. Must have been hideously slow. But still, that was all the language they had; and I don’t see how we would usefully say they are language-deprived. They had a language faculty, and their language production was entirely in order. (It certainly helped that they acquired fingerspelling as children.)

If deaf kids can acquire language through a signed modality, and we call them native speakers of a sign language, I don’t see why we can’t say Bridgman and Keller didn’t acquire language through a tactile modality, and the language they acquired was pretty much written English. (This was after all the 19th century.)

Audrey, you’re not agreeing with the premiss I see, but neither of us know enough about deaf–blind language acquisition to have a debate on this. But I did not have the impression that Bridgman and Keller were one-offs; the impression I have is that deaf–blind kids acquire language all the time. What I don’t know is whether there too the primary language acquired, through tactile means, is abbreviated compared to written English—leaving out determiners, for example.

I don’t think it’s quite what Z-Kat was after. But I do think it establishes his scenario as feasible.