Sensitive Skin

Do you know what is the most sensitive part of your body?
Is it your back?
Your knees?
Your lips?
Or fingertips?
Do this experiment and you will know.
To find out, perform a two point discrimination exam on a friend.
And let him or her do the same for you.

What to do?
Bend a paper clip into the shape of a U with the tips about 2 cm apart.
Make sure the tips of the U are even with each other.
(You can also use a divider)

Lightly touch the two ends of the paper clip to the back of the hand of your subject.
Your subject should not look at the area of skin that is being tested.
Do not press too hard! Make sure both tips touch the skin at the same time.

Ask your subject if he or she felt one or two pressure points.
If your subject reported one point, spread the tips of the clip a bit further apart, then touch the back of the subject's hand again.
If your subject reported two points, push the tips a bit closer together, and test again.

Measure the distance at which the subject reports "I feel two points".

Which part of your body is the most sensitive?
Try different parts of the body: the arm, leg, fingers, back, neck, head, hand, toes.
Compare the distances required for a "I feel two points" response on different body regions.
What part of the body is most sensitive?
In other words, where on the body can two points be detected with the smallest tip separation?

The receptors in our skin are NOT distributed in a uniform way around our bodies. Some places, such as our fingers and lips, have more touch receptors than other parts of our body, such as our backs. That's one reason why we are more sensitive to touch on our fingers and face than on our backs.

Examples
Here are some data from a two point discrimination experiment:

Site	Threshold Distance
Fingers	2-3 mm
Upper Lip	5 mm
Cheek	6 mm
Nose	7 mm
Palm	10 mm
Forehead	15 mm
Foot	20 mm
Belly	30 mm
Forearm	35 mm
Upper arm	39 mm
Back	39 mm
Shoulder	41 mm
Thigh	42 mm
Calf	45 mm

How did your measurements compare?

Movie
At this link you can see a Dutch Television Show with an experiment that looks likes this one: http://villa-achterwerk.vpro.nl

Please be a little patient for the movie to load.

"The best and most beautiful things in the world cannot be seen or even touched. They must be felt with the heart."