SOME RESULTS OF EXPERIMENT 141 
between the method of intelligence and that of reason. It 
may, no doubt, be said that the terminology used is open to 
criticism ; for, on the one hand, the words “ intelligence ” and 
“intelligent” are frequently used as synonymous with “reason ” 
and “rational ;” and, on the other hand, acts requiring neither 
abstraction, generalization, nor the application of any scheme 
of knowledge are frequently spoken of as “rational.” Hence 
there is, it may be urged, some danger of misunderstanding. 
This may be granted. And unless some such restriction of 
meaning under suitable terms be accepted by psychologists, 
misunderstanding will continue. More essential, however, than 
the distinctive terms we are to use is the distinction of method 
which underlies them. That, I trust, is sound. Dr. Lindley, 
in an interesting paper on “‘ A Study of Puzzles,” * has utilized 
the distinction in his investigation of the mental development 
of children, and has found that the procedure of young children 
is predominantly of the “‘sense-trial and error” order which 
has above been termed intelligent; and he expresses the 
opinion that “most of the adaptations of animals are on 
this sense-trial and error level.” 
Such certainly seems to be the conclusion to be drawn from 
my own experimental observations on dogs. It has frequently 
been asserted that the behaviour of a dog with a stick in his 
mouth, when he comes to a narrow gap, shows that he at once 
perceives the nature of the difficulty, and meets it in a rational 
manner by adopting the appropriate plan of action. He pulls 
the stick through by one end. But experiments, which I have 
elsewhere described,t showed that a fox terrier, fourteen months 
old, seemed to be incapable of perceiving the nature of the 
difficulty which vertical iron railings presented to his passage 
with a stick in his mouth, and only imperfectly learnt to over- 
come it after many ineffectual trials and many failures. The 
results obtained on the first afternoon may be quoted to indicate 
the nature of the evidence. The dog was sent after a short stick 
into a field, and had to pass through vertical rails about six 
* American Journal of Psychology, vol. viii., no. 4, pp. 431-493. 
+ “Introduction to Comparative Psychology,” p. 255. 
