FUNCTION OF VIBRIS3AE IN BEHAVIOR OF WHITE RAT 55 



had to turn to see them. The problem was to choose the cor- 

 rugated pathway. The animals were given three trials a day 

 in the beginning but later the number was increased to five and 

 they always ran under the stimulus of a healthy, normal hunger. 

 The records showed the nurnber and distribution of the errors, 

 the time taken from the moment they were put in the box, and 

 general observations of their behavior. It was determined that 

 as only three choices were offered the percentage of right choices 

 must be high, that the perfect runs must reach 75% of the 

 whole, and that this standard must be maintained for a period 

 of five days or 25 trials. As a matter of fact in most cases where 

 the problem was learned a proficiency of 80% was reached. 



The first set of animals used consisted of three groups, (a) 

 animals with vibrissae, (b) animals without vibrissae, and (c) 

 anosmic animals. Several months later a second set of animals 

 was used which was composed of four groups, (d) rats with the 

 infra-orbital branch of the fifth nerve cut, (e) blind rats, and 

 (f and g) normal controls for each of the above groups. 



The behavior of the animals in the box will first be described 

 as a whole and then with the statement of the results of the 

 experiments only those features will be emphasized in which one 

 particular group differs characteristically from the others. No 

 excuses will be offered for describing the behavior in such detail 

 since it is believed that in such experimentation this careful 

 observation of behavior is the important thing, far more im- 

 portant than pages of tabulations either of time or error records. 



The experiment was complicated by several factors: First, 

 the animal had three possible choices instead of the usual two ; 

 but as the interest lay in positive signs of discrimination, not 

 in establishing records, it was felt that such signs would be 

 more clearly observable with three possibilities than with two. 

 For example, if an animal tries one pathway without success, 

 when there are only two, he may take the other simply because 

 it is the only other and not because of any sense quality which 

 attracts him — there is no other alternative. 



A further matter which materially lengthened the, time of 

 learning was the fact that the problem was not considered 

 learned until the animal stopped at the entrance to the wrong 

 runway: it was not sufficient to make the discrimination at the 

 plate, it must be made before running down. In reality many, 



