Dart your eyes rapidly in a random fashion through the following list and call out the COLOUR of the word:
GREEN
BLUE
RED
ORANGE
YELLOW
I think this is a good example of cognitive dissonance, and illustrates that the human brain is not always that great at resolving conflicting information. Try the same exercise at night in turbulence when you are tired and jetlagged with a plethora of warnings and aurals going off - there but for the grace....