Select Special Senses

Exercise 2: Two Point Discrimination of Touch

What areas of our bodies are most sensitive to touch? Hands? Feet? Fingers? To find out, perform a 2-point discrimination exam on a friend.

Procedure:

1. Bend a paper clip into the shape of a U with the tips about 2 cm apart.
2. Make sure the tips of the U are even with each other.
3. Lightly touch the two ends of the paper clip to the back of the hand of your subject. **Make sure both tips touch the skin at the same time.**
4. Your subject should not look at the area of skin that is being tested.
5. Do not press too hard!
6. Ask your subject if he or she felt one or two pressure points.
7. If your subject reported 1 point, spread the tips of the clip a bit further apart, then touch the back of the subject's hand again. But if your subject reported 2 points, push the tips a bit closer together, and test again. The idea is to find the minimum distance the subject can beel 2 points.
8. Measure the distance (in cm) at which the subject reports "I feel two points."
9. Repeat steps 3 thru 8 again but use different areas of the body. Record all results in Data Table 2 of the Student Lab Report Form
10. You will see there are a total of five areas selected for you in the Data Table 2 of the Student Lab Report Form that you must test. Then select 5 other areas of your choosing to test.

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.

These data (rounded) are from a 2-pt discrimination threshold experiment (published in The Skin Senses, edited by D. R. Kenshalo, Springfield, IL, 1968).

*adapted from - Washington University Senses Lab