> I have seen people mentioning difficulty on problems where you need to mentally rotate a cube, but I can do that just fine - it's just that I don't "see" or "picture" the cube, but I still have the concept in my mind of the cube being in a certain orientation and that suffices to solve the task.

As someone with probably some form of aphantasia, a cube is fine because it’s a simple shape with well defined simple mathematical rules that is easy to abstract and rotate. It gets more complicated with complex objects and that’s where visualizing things really matters. Here’s a question, can you accurately visualize a loved one’s face, see it in your mind and describe all the features if you were for instance talking to a police sketch artist. I couldn’t even do that for my daughter or my wife.

I definitely can't - if I had to describe my wife or son, I would be hard pressed to go beyond very generic descriptors (long black hair, brown eyes, and so on), nothing useful to create an accurate sketch. And I wouldn't be able to draw them from memory even if I were good at drawing. This could also be explained simply by having bad memory for faces, though.

But yes, little bits of subjective introspective evidence (like that one, and also mostly ignoring visual descriptions in books, and the perception of having no mental images at all that is asked by the standard self-report tests, and so on) add up and make me 99.9% sure I have aphantasia. It's just that it would be nice to have the objective unambiguous external test, the silver bullet, to be totally sure that they're not a bunch of busses in a trench coat as so many honest beliefs are.