“Mad Science” Mini-Lessons

11. Sensitive Skin


Sensitivity, sensation, tactile illusion


Length of soft wire, ruler, blindfold (optional)


For best effect, this activity should not be done individually.  It should at least be done in pairs.

Distribute the supplies to each group.

Open by reminding them that when something touches your skin, you can feel it.  And you also can feel what shape it is.  In this activity, they will find out how accurate that feeling is.

One person in the group will have his or her eyes closed while another touches his or her skin with one end of the wire, or with two ends at the same time.  The person being touched must decide if it is one or two.  The person doing the touching bends the wire into a “U” or “V” shape, varying the distance between the two ends.  Try to find how far apart the ends can be for the person being touched to still think that it is only one touch.

Find this critical separation for different places on the body.  Are they the same for the different members of your group?

Think of reasons why our skin has these different sensitivities in different locations.

The science details

The sense of touch does not have the same sensitivity and resolution everywhere on the body.  In certain parts of the body, such as fingertips and lips, the sense of touch is used to give us detailed information about what we are touching.  In other parts, the sense of touch is just used to let us know where things are so that we don’t injure ourselves.

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Revised: 21 December 2016; Maintained by Richard Barrans.
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