n6 Animal Intelligence 



7th, 1 6th, iyth, i8th and igth trials he did perform the act 

 before the 10 seconds were up, then for several times went 

 during the two-minute intervals without regarding the sig- 

 nal, and finally abandoned the habit altogether, although 

 he showed by his behavior when the signal was given that 

 he was not indifferent to it. 



Dogs i, 2 and 3 were also given 95, 135 and 95 trials, re- 

 spectively, the acts done being (i) standing up against the 

 wire netting inclosing the pen, (2) placing the paws on top of 

 a keg, and (3) jumping up onto a box. The time intervals 

 were 5 seconds in each case. No dog of these ever per- 

 formed the act before I started to take the meat to feed 

 them, but they did show, by getting up if they were lying 

 down when the signal was given, or by coming to me if they 

 were in some other part of the pen, that something was sug- 

 gested to them by it. Why these cases differ from the cases 

 of Cats 3 and 4 (10 and 12 also presented phenomena like 

 those reported in the cases of 3 and 4) is an interesting 

 though not very important question. The dogs were not 

 kept so hungry as were the cats, and experience had cer- 

 tainly not rendered the particular impulses involved so 

 sensitive, so ready to discharge. Dogs 2 and 3 were older. 

 There is no reason to invoke any qualitative difference in the 

 mental make-up of the animals until more illuminating ex- 

 periments are made. 



ASSOCIATION BY SIMILARITY AND THE FORMATION 



OF CONCEPTS 



What there is to say on this subject from the standpoint of 

 my experiments will be best introduced by an account of 

 the experiments themselves. 



Dog i had escaped from AA (O at front) 26 times. He 



