FIGURE 19:1 Courtesy of Eric Wise
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2. Using the two-point discriminator (be careful as some
two-point discriminators can have sharp points), or a
mechanical compass, touch your lab partner's fingertip
simultaneously with both points of the instrument and see
if he or she can sense one or two points. In order to estab-
lish an accurate reading, make sure that you gently touch
both points of the discriminator at the same time. If you
touch with one point of the discriminator and then another,
your lab partner may perceive two points in time and not
in space.
3. A good way to establish accuracy is to occasionally touch
just one of the points on your lab partner's fingertip.
Another way is to vary the spread of the discriminator. You
might begin with 3 cm and then adjust it to 0.5 cm followed
by a 2 cm spread. Record your results.
1
3
Minimum distance perceived as two points on
fingertip:
4. Now move to the posterior surface of the arm. Establish the
minimum distance that is perceived as two points by your
lab partner. Record your results.
4
Minimum distance perceived as two points on the
posterior arm:
Is there a difference between the fingertip and the
posterior arm?
5
If there is, how might the difference in distance perceived
be explained in terms of the number of nerve endings per
unit area?
6.