I am extremely poor at visualization, can't even picture a line or a circle (I just tried it) and I don't remember images from my dreams. Strangely, when I was a child, I was sometimes able to visualize, but only with extreme effort. More recently, I have experienced what I would call "brain movies", involuntary realistic visualizations, under the influence of opiates.

It seems I am fundamentally capable of visual thinking, but my brain is just not in the habit, though I wouldn't mind being able to summon the ability. It sounds kinda cool.