I can mentally see and feel the little fuzzies around the top where the stem is. I can mentally fidget with the bottom where the flower was.

I can make it a granny smith, a pink lady, a Gala, a Cosmic Crisp and the shape and color striations change. I can see the tiny little pore circles when it's a green or yellow apple. I can conjure and catch my fingernail on a worm hole in the apple.

If I think about a wild green apple from apple trees I know about in Seattle, I can see myself standing there, seeing them both on the tree, and sitting on the ground rotting in several different states of decay and I can squish them and feel it crunching and squishing underfoot, with some parts just sinking into the soft spring soil at a tree on one side of town, or grinding into the gravel and asphalt on the other side of town. I could pinpoint these trees for you on a map.

I can put myself in the scene from Oppenheimer in the lab at Cambridge where he poisoned the apple in the movie, and I can pick up the apple and see the injection site. If I really try I can detect the faintest smell of almonds as I hold it up to my nose. I can do it as Bohr. I can grab the apple out of Bohr's hand as Oppenheimer and feel his adrenaline and the resistance of his confused hand as I do it. I can throw it against the wall instead, maybe shattering a glass window and hearing and seeing all of that, then cutting myself while cleaning it up and smelling and tasting the blood because I instinctively sucked on it.

Mind's eye is so much more than just visual, that the article and discussion of mental imagery in this thread is a bit flat.

Even the survey assumed that every aspect of someone's mind's eye is entirely visual, and it's just not the case.

I honestly can't imagine this concretely at all.

Tell me to imagine a spinning cow. My experience is a lot like evaluating the mental version of:

  class Cow:
      spinning = True

OK, so I don't know if other people actually visualize arithmetic or not. I don't think so, but I also wouldn't think that people literally imagined an apple, either, and yet here we are. But let's assume that people don't usually literally imagine pictures of the numbers in their mind when they add them.

Take 12. Add 7 do it. Now you have 19, right?

My mental imagery of adding 12 + 7 = 19 is nearly identical to that of picturing a spinning cow. Take a cow. Spin it. Now you have a spinning cow, right?

In both cases, those are just facts. Now, higher math does look like something to me, as does writing code. Those do have geometric shapes for me, kinds of blobby things with curved edges but not colors, except maybe rainbowy shimmers on those curves. I can feel the shapes moving and bending, and that moving and bending makes them makes sense to me. "OK, so I'm trying to do a binary search of this set... Alright, so if I push this shape into there... Oh! That'd work! Alright." But in no case do those shape-like things resemble anything I've ever seen in the real world.