alt Hacker NewsI really don't think this is the right definition. I don't think I have aphantasia: I picture things in my mind's eye, can manipulate those images, and I get the various stimulus responses described in some of the literature. But it's totally different than dreaming: it's an act of will, I can dismiss it at any time, and I would never be able to convince myself I was actually 'seeing' what I imagined.
But heck, if that's it then hail, brother.
It's absolutely not a definition - if you can actually picture things, you don't have aphantasia. I brought it up because it's surprisingly frequent that the people who doubt it exists turns out to doubt it because they don't actually believe people actually picture things, and that it's all just talking in metaphors.
It's what I used to think most of my life...
Note that some people who do picture things do visualise it so clearly that it is comparable to seeing, and that was my one singular experience with it as well, but that is the far other end of the scale. Most people will definitely be able to tell it apart from "actually" seeing, but it will be distinctly visual.
When I draw a comparison to dreaming it's about the images, not about being able to will it or dimiss it.