Are you looking for a simple science experiment for kids? Showing kids that they can trick their own nervous system is a fascinating science experiment. The purpose of the experiment is to show that all your senses are relative. Hot and cold, or light and dark, are relative for your nervous system; there is no absolute standard. Try the experiment for yourself and you'll understand.
Fill the three bowls with the following: 1) Hot water, but not scalding 2) cold ice water 3) lukewarm water.
Put one hand in the cold water and the other hand in the hot water.
Leave your hands in the bowls of water for two minutes.
Pull both hands out of the water and put them both in the lukewarm water.
Notice that your hands feel like they are in water at two separate temperatures, even though they are in the same bowl of water!