THE INTERFERENCE OF VISUAL HABITS 173 



be as different in intensity as possible from the standard. 3 The 

 situation is summarized in table 3. The first reactions of the 

 rat to the twice-shaded, 8 c.p. light were made as though this 

 light were the standard light of habit 1. (Reactions to the 

 normal stimulus should give at least 80% correct. Reactions 

 to darkness would all be made to the left and so would give 

 50% correct. Since the new series, habit 2, was the reverse 

 of the " normal " series, when the rat treated the stimulus as 

 though it were the normal standard light, he should make not 

 more than 20% correct.) I now knew that the once-shaded 



TABLE 3 

 Test Correct in 10 



Normal (32 c.p., once shaded) 9 



" 5 



3 



5 



5 



5 



4 



New series (8 c.p., twice shaded) 1 



32 c.p. and the twice-shaded 8 c.p. would initiate the same 

 responses. Furthermore, there was reason to assume, both from 

 the behavior just cited and from the work of other investigators, 

 that the lights were dissimilar enough in intensity (one being 

 almost equivalent to darkness) that they could be readily dis- 

 criminated by a rat when tested in the conventional discrimi- 

 nation box. 



In this second test every effort was made to keep the conditions 

 identical with the first test save in the matter of light stimulus 

 and direction of turning. The results are very striking. In the 

 first test, the least number of trials given any rat was 60 and the 

 greatest 300. In the second test, one rat learned in 420 trials. 

 The other seven rats never completely learned the association, — ■ 

 the trials given were 680, 760, 850, 1080, 1080, 1090, 1090, and 

 1160. At the close of the work these rats were improving so, 

 that it seems probable that they would have mastered the 

 problem had the training been more extended. The results of 

 this test are summarized in table 3, The length of the training 

 periods here as opposed to the learning periods with habit No. 1 



3 It would be of value and interest to have animals form habit No. 2 with the 

 same stimulus used in habit No. 1. My choice of stimulus for the second habit 

 was guided by a desire to secure a procedure similar to that followed by Dr. Hunter. 



