What you Need
Some rough carpet
Something very smooth and slippery
Some ordinary paper
What to do
Rub one hand on the carpet, while rubbing the other on the smooth plastic for about 30 seconds.
Now rub both hands on the paper. Does it feel the same to both hands?
What may happen
You should find that the hand that was rubbing the carpet will feel the paper as being very smooth, while the hand that was rubbing the plastic will feel it as being quite rough.
Why does it happen?
This strange effect is due to how your senses work, the nerve cells in your fingers are much more sensitive to changes in the vibration they are feeling than the actual amount of vibration. You can actually detect this in their activity. If the amount of vibration changes they send a big flurry of activity to your brain, and then after a while calm down.
So when you rub the carpet your fingers get used to lots of vibration and become less sensitive to it, and when they move to the paper they send a signal saying 'this is much smoother',where as the fingers on the plastic get used to the lack of vibration so when they move to the paper they send a signal saying 'this is much rougher'.
This is also you walk into someone's house it smells strange, but after five or ten minutes you don't notice it any more.
Why do your senses work this way?
In general the most important things are changes in what you are sensing, imagine a caveman sitting in his cave getting signals from his brain, if his temperature sense is telling him it is still quite warm, his nose is telling him it still smells slightly of smoke, his bottom is telling him the floor is still quite cold, he may not notice his ears telling him about the new footsteps of the sabre toothed tiger creeping up behind him. So your nervous system ignores the stuff that hasn't changed and concentrates on new things, like those footsteps, which mostly works much better, but means it can be confused by this experiment.
Part of the show Memory and Learning from the 2nd Dec 2007