EXERCISE 97 



We saw (Exercise 86) that some of our reflex, or instinctive, movements result from the contractions 

 of muscles which we can control. We can produce some of these movements at will, and we can also 

 inhibit, or prevent, some of the movements. 



Problem. How many trials does it take to overcome the winking reflex ? 



What to use. A sheet of glass ; a rubber-tipped pencil or stick ; two students working together. 



What to do. Have subject hold pane of glass in front of face while operator from time to time 

 strikes opposite side of glass before one or the other eye. Subject tries to keep from winking, confi- 

 dent that pencil cannot reach him. Note number of strokes before there is complete control. Change off. 



Record. Describe observations and results. 



How many attempts were necessary to secure complete inhibition ? 



How many attempts were necessary for your fellow worker ? 



Tabulate results for the whole class : 



What was the highest number of trials ? 

 What was the lowest number of trials ? 

 What was the average number of trials ? 



Questions. 1. What is the advantage of being able to overcome an impulse within a short time or 

 after a few trials ? 



2. What is the disadvantage ? 



3. Do boys or girls learn to control their impulses more readily ? How do you know ? 



4. What kinds of inhibitions are established most easily ? What kinds least easily ? 



5. What evidence is there that other animals can learn to overcome natural impulses ? 



[104] 



