PATTERN RECOGNITION
Both of the figures below are easily recognized a picture of Lincoln. Th one on the right contains more detain and can be thue recognized more readily. The fact that either can be seen for what it is is due the the extremely strong human ability to fit known patterns to a view scene.
Some times a scene can be interpreted as different patterns by different viewers. Look at the picture shown at the right. Most individuals will see a white goblet. However, if you look at the black instead of the white, two human faces appear. We normally focus on the brightest, largest object in a scene and suppress the background. A different way of looking may reveal a different pattern.