I personally find it hard to believe that people would really experience things so differently. Seems simpler to attribute it to differences in how people describe their internal representations in words.
Even for myself it's a little bit unclear and changing how I'm really representing things. One day I might say oh I don't see anything, it's all just concepts (oh no it's aphantasia). On another it would be like ok maybe if I focus these concepts can have some form to them, so yeah I'm actually totally seeing things (wow he has mental imagery).
So if you made 100 clones of me take a questionnaire, you might see 50% reporting aphantasia and 50% saying they have mental images, even though they're actually the same.
I'm almost aphantasiac, so for me it's actually easy to believe—visualizing things is hard enough that I can imagine not being able to do it at all, but also possible enough that I can imagine it being easier to do.
Similar questions throughout this thread make it clear that people assume recognition and/or knowledge of what something looks like is tightly coupled to internal visualization, but (writing as someone with aphantasia) they're not. I can draw both of the examples you gave, thinking about them (including thinking about how I would go about drawing them) just doesn't include an image in my head.
Ed Catmull, former head of Pixar, also has aphantasia[0] and had the staff take the only real diagnostic that exists (the Vividness of Visual Imagery Questionnaire[1]) and found that, on average, the animators had less ability to visualize than the production managers. Obviously they varied significantly - the article mentions one that could play the entire movie in their mind - but lack of mental imagery clearly does not preclude professional level artistry.
Back before GPS, people used to give each other driving directions based on landmarks... go straight 2 miles, turn left at the red brick schoolhouse. Now, that sounds like the condition you describe - you know red, you know brick, you know what schoolhouses generally look like, but since you've never been to this specific place there is zero mental picture. When you finally get there, it's a surprise, you've found the thing that combines all the elements. But the next trip, there is a mental picture. It's probably extremely vague and lacking any detail, but it's still something, the next time it won't be a complete surprise.
Someone with the condition you describe (zero mental imagery) would, constantly, feel like they are seeing basic objects for the very first time, you wouldn't recognize anything at all, this would be a highly debilitating condition just like severe amnesia.
I can only tell you that I do not have mental imagery and am not constantly surprised by my surroundings. Object permanence has absolutely no dependency on visualization; it is completely unsurprising to me that the stop sign near my house looks the same each time I encounter it.
I totally get that you, having lived a life where mental imagery is such an integral part of your baseline experience, assume that many of the things you rely on it for require it. However, the human brain is impressively adaptable, and it turns out many, many aspects that people assume are linked (and may well be for them as individuals) are not globally so.
This thread is full of such realizations - people assuming ability at chess, art, tetris, spatial reasoning, abstract reasoning, architectural design, conceptualizing of DB schemas, etc. must be correlated with facets of thought like strength of mental imagery, presence of an inner monologue, ability to dream, etc. In all of those cases, people have chimed in with (anecdotal, to be sure) counterexamples. It turns out brains are generally capable of doing a lot of different things in a lot of different ways.
In another comment you wrote "stop sign is a red octagon (with a white boundary) with the word "STOP" in the center. I could draw you a plausible picture of one without issue". The fact that you knew all of that without having to actually find a stop sign and look at it, that's mental imagery. It may be a skill some people are very good at (i.e. they can remember lots of small details) and others are not, but it's not that you don't have this skill at all.
What I know is that people describe not having aphantasia like
“I’m sitting in a room with a dog and a TV. Then someone says ‘visualize a stop sign.’ And, so then I’m sitting in a room with a dog, a TV and a stop sign. I’m know the stop sign isn’t real. It might be fuzzy or even black & white. But, I can see it between the dog and the TV.”
Well… I know exactly what a stop sign looks like. But, there’s no stop sign in the room with me and my dog. It’s not there at all.
No, that is more like hyperphantasia, where the visualized object is superimposed on top of one's visual reality. Seeing something in one's mind's eye is more like there is a a buffer right above my visual reality where I can imagine something inside that buffer. It is not superimposed over reality but I can focus on both the visual buffer and the imagination buffer simultaneously.
The woman in the article describes that she has no problem identifying faces she has seen before, in fact, she is better at that than average. It is just that she doesn't see these faces as a picture in her head.
So clearly, there is some encoding process going on here, and the comparison is done on the basis of this encoding. This can be much more efficient than comparing the actual thing. Think of it has taking the hash of a picture, and performing comparisons using the hash, not the picture itself.
It sounds like people simply have different definitions of "a picture in her head." Her mental processing sounds entirely normal on all counts.
I guess I must have the condition. I closed my eyes and tried to see a red apple, which the article uses as the diagnostic test. Nope, all I saw was black. Could I think of what a red apple looks like? Of course. If the test is to actually, truly see an apple while your eyes are closed, my guess is everyone would fail.
I suspect the 3.9% estimation is wildly inaccurate but that the condition / spectrum is true.
In the 1-5 guide, I'd probabably rate myself a 99 or something silly. I feel like the equipment is capable of visualising, but I just don't know how to operate it.
However, I do have involuntary visualizations. My dreams are images, very unlike thought. And in the last 5 or so years I can recall 2 occasions where I was in a relaxed state and pictured things without really trying, so I know it's possible to have dream like images when awake.
My wife says she can just perfect recall stuff. I entirly believe she can visualise, but I believe she confuses what happened with what she can see. She also states she can visualise the apple, or pretty much anything else she wants.
Even for myself it's a little bit unclear and changing how I'm really representing things. One day I might say oh I don't see anything, it's all just concepts (oh no it's aphantasia). On another it would be like ok maybe if I focus these concepts can have some form to them, so yeah I'm actually totally seeing things (wow he has mental imagery).
So if you made 100 clones of me take a questionnaire, you might see 50% reporting aphantasia and 50% saying they have mental images, even though they're actually the same.