I can choose to see mental images actually overlaid over my field of vision, or somehow in a separate space.
The obvious question someone might ask: can you trace an overlaid mental image? The problem is registration—if my eyes move, the overlaid mental image can shift relative to an actual, perceived, sheet of paper. Easier to do a side by side copy than trace.
To add to the differences between people:
I can choose to see mental images actually overlaid over my field of vision, or somehow in a separate space.
The obvious question someone might ask: can you trace an overlaid mental image? The problem is registration—if my eyes move, the overlaid mental image can shift relative to an actual, perceived, sheet of paper. Easier to do a side by side copy than trace.