A couple of researchers from Norway showed a number of works of art to artists and non-artists and then used eye-tracking cameras and software to figure monitor what parts of the artwork they were actually looking at. 
The yellow lines in the pictures above show how the eyes of the viewers scan the painting. The main finding is that there is a difference in the way artists look at a painting when compared to regular people. The image on the left shows how regular people spend much more time looking at the “key features” of a painting, while the image on the right shows how artists actually spend much more time looking at the other details.
Here’s another example:
Obviously, the image at the right represents the eye motion of artists. The idea is that artists have much more training in how to reproduce the details of a scene and hence they look at those with much more interest then the average person who wants to look at people and faces.
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