"We can also see activation in the visual cortex during fMRI studies, the area in the brain that processes images from the eyes, further suggesting actual visualization."
(edited to add) Also, Aphants lack pupil response when asked to imagine dark/bright scenes: https://www.sciencedaily.com/releases/2022/04/220420092150.h...
On the other hand, I can do hypnagogic meditation where I am on the verge of falling asleep, and something like visual dreams start before actually falling asleep, and in that case I can actually see things as if I saw them with my eyes, and I can look at details and so on.
And that's why I'm not sexist (lol), when asked gotcha questions all imagined doctors are sexless lines on an unwritten page that exists in the soupy pre-semantic peircean firstness of my brain.
It's sort of the difference between logical supervenience and metaphysical, or weak emergence and strong emergence. Qualia being something additional to the neural description.
Conclusion: some people are a-juggular and are wholly incapable of imaging juggling. Poll: are you a-juggular or not!?
I hope this illustrates how we're missing a very sensible third option here: visualizing is a skill that some people are better at than others, but (almost) anyone can learn.
How do you do any of that with visualizing? If I'm trying to learn to juggle, I can watch someone else juggling and say, I want to do that. How do I watch someone else visualizing and see what to do?
Have you actually dedicated significant time to trying to learn how to visualize? I suspect that if you did, you'd realize: oh, wow, maybe I can actually get better at this. If most people who give it a serious effort also come to that conclusion, I feel like we've pretty much settled the question. So it is testable, just not as easily.
I haven't had to. I don't have aphantasia. Visualizing doesn't feel like a learned skill to me. It feels like something I've always known how to do. Of course if I pay more attention to what I'm doing, I can visualize in more detail than if I just do it casually. But I've never had the feeling that, oh, if I practice this and learn I can get better at it, the way, for example, that I can get better at playing the piano by practicing.
Where I'm stuck is, if someone else who couldn't visualize asked me to teach them how, I wouldn't know what to do. Whereas, if they asked me to teach them how to play the piano, I'd at least have some idea.