If I ask you your birthday, I’d expect you to hear “August 17th” in your inner voice before answering. But if I asked you “is your birthday January 3?” would you have to mentally say your birthday before answering “no”? I’d assume not.

My inner voice is used almost exclusively for forming sentences before speaking or typing them. If I’m alone, not thinking of conversations, and not reading, there’s rarely anything there except maybe a song stuck in my head. My inner voice isn’t constantly there saying “let’s go switch over the laundry” and stuff.

I guess I “know my birthday” by virtue of the fact that I hear the words “August 17th” (not my real birthday, but yeah) in my head when I casually wonder what my birthday is.

That would describe my experience. Aphantasia only affects the ability to visualise something, not the mental voice that I believe everybody has.

Well you might be seeing an actual line. I'm mentally tagging the squares in that line as 'line of control'. It's like seeing somebody point a finger at something. I don't need to visualise an actual line coming from their fingertip to be able to judge where they're pointing at. It's more a spatial thing than visualising an image.

IDK, it's tough explaining how brains and thought processes work. They just... are.