Investigation: Two-Point Touch Discrimination Test
Background: Mechanoreceptors in the skin respond to touch, pressure, and vibrations. Areas of the skin that have more mechanoreceptors are more sensitive than other areas, which is why you might feel a mosquito land on your face, but not notice one that is on your arm.
Question: Which areas of the skin are the most sensitive to touch?
Hypothesis:
Procedure:
1. Obtain a plastic compass and a ruler. The compass can be closed to where the points are very close together or spread out so that the two points are farther away. You will use the points of the compass to determine sensitivity. Caution: Compasses can be sharp, you do not need to apply very much pressure.
2. Have your subject close their eyes or look away so that they cannot see the compass touch the skin. Start with the wrist and place the two points of the compass as close together as possible and touch the skin. Gradually spread the points apart and test the subject until they note that they can feel TWO points. Use a ruler to measure the width in millimeters and record that value in the data table.
3. Repeat this procedure for each of the areas on the data table for your first subject, then switch so that you also have readings for a second subject.
Data Table
| Two-Point Distance (mm) | ||
| Area of Body | Subject 1 | Subject 2 |
| Wrist | ||
| Palm | ||
| Back of Hand | ||
| Thumb | ||
| Cheek | ||
| Back of Neck | ||
| Upper Arm | ||
Discussion
1. Make a CLAIM about which part of the body you think is the most sensitive
2. Provide a summary of EVIDENCE that supports this claim (from your data table). You may also wish to consult other groups and examine data from the entire class.
3. Suggest REASONS for these results. Consider why it might be important for some areas to be more sensitive than others.
4. Extension: A different type of receptor, a thermoreceptor is responsible for detecting changes in temperature. Design an experiment where you could determine which parts of the body are most sensitive to temperature changes.
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