Picture of Be a Scientist: map your skin
Gently press a few slightly-spread fingertips into a friend's back, without telling them how many fingers you are using.

Ask them how many fingers you're using, and chances are they will get it wrong.

Why is that? Grab a willing volunteer and we'll find out...
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Step 1: Equipment Required

Picture of Equipment Required
rubber bands.jpg
Squeeze your earlobe. Squeeze it hard. That doesnt really hurt, does it? Now try squeezing just as hard at the top of your ear ... ouch!

The nerves in your skin are spread out differently in different parts of your body. This activity will show you just how differently.

You need a volunteer who is not too easily embarrassed (if they are feeling really cooperative, they could be wearing shorts & tee-shirt to expose as much polite skin as possible), two full-size pencils, an elastic band, a ruler, and an outline of a body. Any simple silhouette will do, as long as you can write on and around it.

Step 2: How to measure the sensitivity.

Picture of How to measure the sensitivity.
sense 02.JPG
First, you need your test equipment. That's the pencils. Lay them blunt end to blunt end, over-lapping a couple of centimetres, and fasten them together by twisting the rubber band around them, as in the diagrams below.

The pencils can then be bent to make a sort of pair of tweezers.
Open the tweezers wide and touch them to the subject's skin when they have their eyes closed, and they can feel two points on their skin. Lift them off, squeeze the points slightly closer, and touch again. Can they still feel two points? Lift the tweezers off, squeeze some more and try again. Keep doing this, and eventually the subject will only be able to feel one point, even though two points are touching their skin.

Measure how far apart the pencil-points are, and record it on the silhouette. Try this over as much of the subject's skin as you can, front and back of the body (it will also work through a single layer of clothing, such as a t-shirt). Remember to respect your subject - do not map bits that they do not want mapped.
dombeef4 years ago
Great,now I have dots all over me.
Kiteman (author)  dombeef4 years ago
dombeef Kiteman4 years ago
YAY Connect the dots time!!! IT'S A DOG!!!
Kryptonite6 years ago
If I squeaze the top of my ears I can hardly feel it, but if I squeeze my earlobes it hurts, is there something wrong with me or do camels have a different nerve system.
Kiteman (author)  Kryptonite6 years ago
There's nothing wrong, as such.

You're standing the wrong way up.
Wow, nice theory but how do I stand the wrong way up? I've heard of standing on your head but it's really quite painful with the souls of your shoes driving into your scalp... Oh well.
Well, when I handstand, my soul always drives according to the posted speed limit.
Look out for those floating Altoid Tins.
Are you a teacher? ..You might also want to do fake pokes, with only one point. I think that the knowledge that they are being poked with two points may subconsciously make them feel two.
Kiteman (author)  Weissensteinburg7 years ago
True. I generally poke them from behind without saying how many fingers I'm using.
hehe, you said "I generally poke them from behind " ok i'm so immature.
Lol... I so want to make a comment on the wrongness of that but I can't because he's married XD
Thats what she said.
Kiteman (author)  Kiteman7 years ago
And a quick edit later...
A good name6 years ago
Ewwww... Grab a volunteer? Lol sorry I could resist that one.
Sofa-King7 years ago
Although i havnt tried it yet, id suggest doing this along with the Human cutout instructable, it would make it easy to map everything, and create a larger space to do it in