Group Members: _____________________________________________________ Period: ___________
Skin Touch Receptors Lab
How sensitive is skin to touch? The receptors for the sense of touch are scattered over the surface of your entire body,
however those receptors are more closely grouped together in certain parts of your body. In this activity you will
investigate the distribution and sensitivity of the touch receptors in the human body.
Retain this lab, as we will be utilizing the data you collect here for a lab in the nervous system unit.
Procedure
1. Obtain 1 caliper per group (ruler with toothpicks taped to it), and 1 unmodified ruler.
2. Have the test subject close eyes tightly.
3. Using the unmodified ruler to measure, on the caliper move the toothpick on the slide so that the distance
between the point of the stationary toothpick is 20cm away from the point of the toothpick on the slide. (if the
body region is smaller than 20cm, do the largest possible distance in whole centimeters)
4. Gently and briefly touch either one or both toothpick ends onto your lab partners skin
5. Each trial should have 3 skin touches. Two should be with 1 toothpick point and one should be with 2
toothpick points. (Randomize the order so that the partner cannot guess, or so that the partner doesn’t know
that the third touch test will always be 2 points!)
6. Have lab partner report how many ends they can feel. Do at least 2 trials (total of 6 touches)
7. Reduce the distance between the two points by 1cm and repeat steps 4 through 6.
8. Continue this until you reach the smallest distance that the test subject can distinguish 1 from 2 points of contact
with 100% accuracy.
9. Record the smallest distance between the two toothpick points that the subject can ALWAYS identify as 2 points
of contact. Only measure and record data in whole centimeters.
10. Complete each of the body regions in the data table. (ONLY COMPLETE THE REGIONS OF THE BODY YOU
ARE COMFORTABLE WITH ALLOWING TO BE TESTED)
11. Calculate the reciprocal as an estimate of the number of receptors. The larger the reciprocal number the higher
the touch receptor density in that region.
12. Create a line graph with your results using the values in the reciprocal measurement columns. Depict each group
member with a different color on the graph.
Two Point Discrimination Test Results
Body
Region
Group
Member 1
(cm)
Example 2
Scalp
Forehead
Cheek
Nose
Chin
Front of neck
Back of neck
Upper back
Shoulder
Reciprocal
Measurement
1/#
Group
Member 2
(cm)
Reciprocal
Measurement
1/#
Group
Member
3
Reciprocal
Measurement
1/#
1/2 = 0.5
1
1/1 = 1
2
1/2 = 0.5
Body
Region
Group
Member 1
(cm)
Reciprocal
Measurement
1/#
Group
Member 2
(cm)
Reciprocal
Measurement
1/#
Group
Member
3
Reciprocal
Measurement
1/#
Upper arm
Elbow
Forearm
Wrist
Back of hand
Palm
Tip of thumb
Tip of second
finger
Tip of third
finger
Tip of fourth
finger
Tip of fifth
finger
Front of knee
Back of knee
Lower leg
Back of lower
leg
Sole of foot
Analysis
1. Of the parts of the body tested, which part was best able to distinguish between the closest stimuli?
2. Which part was least able to distinguish between the closest stimuli?
3. What do your results infer about the distribution of touch receptors in the skin?
4. From your lab observations, which part of the body has the greatest number of touch receptors?
5. What might be the reason the region you identified in question #4 would have more touch receptors? (what is
the advantage)
6. Was there a difference between group members measurements?
7. If there was a difference between group members measurements, why do you suppose that occurs? If there was
no difference, why?
8. Compare your results with at least one other lab group in the class. Were there any similarities? Differences?