Students create a tool with 2 points (eraser and 2 pins with plastic heads, for example) and work in pairs to test the sensitivity of the skin on their arms, fingers, and hands.

This activity fits well into a discussion of the homunculus - an imaginary human with body parts sized to indicate the number of nerve endings in the brain that are associated with that body part.

A new interactive take on this concept (developed as a neuroscience outreach tool by members of the Fitzpatrick Lab at the Max Planck Florida Institute for Neuroscience) is available at www.maxplanckflorida.org/fitzpatricklab/homunculus/. Teachers will want to read the guide for instructions on how to collect measurements and for a complete supply list.