That reminds me of the Change of Blindness phenomenon. Of course the amusing thing is people believe that they are highly perceptive visually, and will notice large changes in a scene. The reality is that a lot of information is discarded. We just don't have the cognitive capacity to handle it.

Want to see it in action? Okay...

Watch the following clip once, when you're done reading. In the clip there are two teams throwing balls at each other, a black team and a white team. Watch the video and carefully count the exact number of times the white team passes the ball to each other.

Oddly enough people get different answers for the same clip. But watch it now. When you have a number for the times the white team passed the ball, scroll down.

Clip: http://viscog.beckman.uiuc.edu/grafs/demos/15.html
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Did you really watch it? Go watch it, then keep on scrolling.
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Did you see the ape walk past?

50% of people don't.