In sensitive areas, the pressure sensors are closer together, so the two tips of the paper clip will activate two separate pressure points. Messages from both sensors are sent to your brain and you feel both tips.

In less sensitive areas, the pressure sensors are further apart, so both tips activate only a single pressure sensor. A message from this sensor is sent to your brain, and you only feel one tip on your skin.

For this experiment you will need:   A paperclip A pen and paper A ruler A friend

You can also try this on your own, with your eyes shut, concentrating on what you feel.

Instructions:

			1.	Straighten out a paper clip and bend it into the shape of a U. Make sure the tips are level with each other.
			2.	Now, ask a friend to close their eyes. Arrange the ends of the paper clip so they are about 1 cm apart.
			3.	Touch both ends of the paper clip gently (and at the same time) onto the back of your friend's hand and ask if he or she felt one pressure point or two?
			4.	If your friend felt only one pressure point, spread the tips of the paper clip and try again. Write down the distance where your friend goes from feeling one pressure point, to feeling two pressure points.
			5.	To make it difficult for your friend to guess the answer, vary both the distance between the tips, and whether you actually place one or both tips on their skin.

Try this test on the palm and back of the hand, fingertips, forearm, upper arm, shoulder, back, neck, cheek, forehead, lips, nose, legs, tips of the toes, soles and upper parts of your feet.

Which part of your body can two points be detected with the smallest tip separation? This is the most sensitive part of your body.

Below are some approximate values for this two-point-discrimination test (from The Skin Senses, edited by D. R. Kenshalo)

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