Prove is a strong word. But it supports the existence of the condition as it coheres with our scientific models of visual experience. You can always reach for obscure philosophical puzzles about phenomenal experience to try to invalidate the science, but at that point you're just having a different debate than the rest of us.

A quick demonstration I sometimes use to tease out this distinction: “imagine a six-sided die. Are you imagining it? Good. How many dots are on the side closest to you?”

If the phenomenal experience was the same and the difference is in the description, everyone should still be able to give a number as their answer, even if they have to use different processes to derive the number from their different descriptions. But aphantasiacs will visibly struggle to answer this question, or give a non-number non-answer like “no side is closest to me” or “depends on which way the die is facing”.

I hesitate to come to this conclusion.

When I was a kid, I could visualize things so vividly, I could almost overlay the visual signal onto my real visual field.

The visual cortex signal was "loud" enough that I could trick the propioceptive parts of my brain.

E.g. I could visualize falling so vividly that I would actually feel the stomach drop sensation.

As I get older, I still have a very visual mind, but not nearly what I used to have as a kid. It also feels more "far away" from my actual visual field.

Though some days if I'm stressed, I don't seem to have as much control/access to the visual side of things.

So I kinda get where aphantashisa people come from.

I certainly have to try. And the results often ain’t great.

I have wondered if painters and interior decorators and such were typically blessed with much better tooling for that.

I don‘t know how closely visual recall and creative visualization are related, though.

I'm not sure if people overestimate it either, some people just have strong memory and powerful mind's eye. My memory is probably from early trauma and represents the extreme other end. If anything it can be a detriment sometimes, I'm not sure a super powerful ability to picture stuff really impacts day to day living for the average human in history. There's no reason for it to disappear evolutionary if it's not a big disadvantage.

As examples I don't listen to music that frequently, I just listen in my head. I can hear songs pretty much completely in my imagination. I'll forget lyrics consciously but letting it play and zoning out the proper music and words appear at the right time. I can also watch days of kindergarten(or any grade) like it's video.

If people are trying to do that and can't tell a single visual detail from a memory or hum a passage from a tune I don't think it's a communication problem, there's just a real difference in experience. To be clear from my personal experience not being able forget stuff or not picture stuff you dont want to sucks. And I have some pretty bad tunes upstairs.

But there are obvious giveaways. Among your friends and colleagues there are people who can’t sing and people with perfect pitch perception despite no training, ones that can barely coherently speak but can write beautiful prose and vice versa, some can stare at code for 12h straight while others find the sheer idea of it horrifying. There’s people who believe in ghosts or even believe they’ve seen ghosts while others are grounded and rational. People with photographic memory and people who cannot recall what they were doing 5 minutes ago (me). The list of distinctions could keep going forever. Everyone’s good at something and shit at something because everyone’s mind is different. It’s silly how most people completely underestimate the diversity of human internal experience - maybe this type of close-mindedness is part of it too.