(This is probably a poorly-formed question, but I'm really just trying to find out if there's any research in this area.)
Most children pick up a spoken or signed language at an early age, and this gets referred to as their native language. Can a person's native language be in the written medium, rather than the signed or spoken?
I'm asking based on my own experience, so this is purely anecdotal. When I was a child, I didn't start speaking until later than expected. Then, in an incident that surprised everyone, when I was two, my parents discovered that I knew how to read when I asked them what "carbohydrates" meant off a cereal box. Decades later, when speaking to my wife, I often realize I don't know how to pronounce a word that I've been using all my life -- because I've been using it in writing, not in speaking.
Is there any research at all looking at children picking up written language before or in conjunction with spoken language? Is there any research on children learning written language on their own?