Figure-Ground Perception

We have a tendency to simplify a scene into a main object (figure) and then, everything else is used to form the background.
For example, you might see a maple leaf on this flag.. If you take another look you'll see two faces with pointy noses arguing. We simplify the flag to see a red leaf and therefore, the white is just a background for the image.

http://en.wikipedia.org/wiki/Figure%E2%80%93ground_%28perception%29
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