[Kaiyou]

Nobody has proven that it's not trainable, so I'd assume that it is. But what's a good training method? Maybe a visual hobby, like video gaming?

I'm someone who is exceptionally good at visual things. For the apple, I can do way better than the example picture (1) on the Twitter image. I can not only do 2D, but 3D. I can rotate the apple in my mind and slice it and then rotate the slices etc. Found out about this by accident, while watching YouTube videos with visual puzzles, that were completely obvious for me with a single glance.

And I spend most of my free time on visual hobbies, like playing video games or watching movies. But maybe I'm just attracted to those hobbies, because I'm a visual type.

[TeMPOraL]

> Nobody has proven that it's not trainable, so I'd assume that it is.

I've never heard of a successful training regime, or even of anyone who successfully trained it, so that's an evidence against it being trainable.

> And I spend most of my free time on visual hobbies, like playing video games or watching movies. But maybe I'm just attracted to those hobbies, because I'm a visual type.

I'd guess the latter, because I also spend a lot of time on visual hobbies, like playing video games or 3D modelling, and it didn't help me in any way. I still don't have a mind's eye when I'm awake.

[Kaiyou]

Absence of evidence isn't evidence of absence. A good training exercise I can think of is to build complex Lego models according to the instructions. It's how I spend lots of my time in my early childhood, before I was allowed to play video games and watch TV. By touching the pieces and rotating them yourself you get good image training of how shapes look when you rotate them. Building things in a 3D space based on drawn instructions from only a single point of view should also help to build mental images.