Full Idea
Recent experiments (Shepard 1982) suggest people have imagistic representations they inspect when solving problems. In comparing two rotated images, the time for comparison varies with the angle of rotation.
Gist of Idea
Problem-solving clearly involves manipulating images
Source
Georges Rey (Contemporary Philosophy of Mind [1997], 2.5.3)
Book Reference
Rey,Georges: 'Contemporary Philosophy of Mind' [Blackwell 1997], p.54
A Reaction
This doesn't prove that they are slowly rotating something. It may just be harder to make the leap to the new shape, when it is 'further away'. Picturing a 20-sided figure, we don't add sides one-by-one.