A post by Christopher Gauker.

A softball player can visualize the trajectory of a fly ball and her own spatial relation to the ball and by means of that visualization arrive at the spot where it will approach the ground just in time to catch it.

An experienced builder of bird houses can knock out a pretty good bird house without having to measure all the pieces, just by visualizing the pieces he needs and cutting them to size accordingly.

I can take apart a leaky faucet and replace the washer and then put it back together again.  In doing this, I form a sequence of mental images representing the pieces and the order in which they came apart.  After replacing the washer I play this mental movie in reverse, until the faucet has been reassembled.

Our ability to solve problems on the basis of visualizations in this way depends on the visual knowledge we have of how things move around and interact in space.  Our possession of this knowledge is most evident in the distinctions we draw between visualizations of realistic sequences of events and visualizations of fantastic sequences of events.