32 WALTER S. HUNTER 



lighted box during the first 50 trials. The data given for the 

 rats of each group were obtained under similar conditions (for 

 our present purpose) and are strictly comparable. The only 

 cases of marked preferences occur with rats Nos. 5 and 9. No. 

 5's preferences for the dark boxes will help to account for his 

 slow learning; but it would seem that No. 9 should have learned 

 very rapidly owing to its marked preference for the light box. 

 With the exception of these two- rats, all the animals were on 

 an essential par as to preferences. Hence the differences noted 

 in their learning periods must have been due to the different 

 conditions under which they worked. Accidental individual 

 variations are not the causes of these differences because of 

 the number of rats used. 



(b) Dogs. — The two dogs, Blackie and Brownie, were given 

 10 trials daily in Box B under conditions of reward only. The 

 former animal was given 560 trials on the association. Of 

 these, 408 trials or 72% were correct. Brownie was given 650 

 trials on learning the association. Of these, 396 trials or 60% 

 were correct. Ninety-five per cent of the last 100 trials were 

 successful. The relatively poor showing made by this dog was 

 due to the acquisition of habits that interfered with the proper 

 reaction. Twice during the learning series, extra tests had to 

 be given in order to break up a discrimination now against the 

 right and middle boxes, now against the left and middle boxes. 

 In general, it may be said of both dogs that their rate of learn- 

 ing is no better than that of the rats. Indeed it is much worse 

 than any of the rats tested with reward and punishment and 

 10 trials daily. The only rat that learned the reaction that 

 did not do much better than the dogs was No. 5. I would sug- 

 gest that the difference is due to the dogs' "helplessness" when 

 deprived of cues from the experimenter. The following para- 

 graph elaborates this point. 



There are several interesting points relative to the. dogs' 

 behavior in the learning series that deserve mention. Indeed 

 to a large extent, they are typical of their behavior throughout 

 the entire experiment. When the dogs were first put into the 

 problem box, instead of attempting to get out, they merely sat 

 down and howled. They were out of sight of the experimenter, 

 it will be remembered, and when placed in such conditions 

 seemed quite helpless. They gradually overcame this timidity, 



