3S E. L. THORNDIKE. 



much slower in forming associations and less able to tackle hard 

 ones, but the biggest part of the difference between what they 

 do and what the dogs and cats do is not referable so much to 

 any difference in intelligence as to a difference in their bodily 

 organs and instinctive impulses. As between dogs and cats, 

 the influence of the difference in quantity of activity, in the 

 direction of the instinctive impulses, in the versatility of the 

 fore-limb, is hard to separate from the influence of intelligence 

 proper. The best practical tests to judge such differences in 

 general would be differences in memory, which are very easily 

 got at, differences in the delicacy and complexity attainable, 

 and of course differences in the slope of the curves for the 

 same association. If all these tests agreed, we should have a 

 risht to rank one animal above the other in a scale of intelli- 

 gence. But this whole question of grading is, after all, not so 

 important for comparative psychology as its popularity would 

 lead one to think. Comparative psychology wants first of all to 

 trace human intellection back through the phylum to its origin, 

 and in this aim is helped little by knowing that dogs are brighter 

 than cats, or whales than seals, or horses than cows. Further, 

 the whole question of ' intelligence ' should be resolved into par- 

 ticular inquiries into the development of attention, activity, 

 memory, etc. 



So far as concerns dogs and cats, I should decide that the 

 former were more generally intelligent. The main reason, how- 

 ever, why dogs seem to us so intelligent is not a good reason 

 for the belief. It is because, more than any other domestic 

 animal, they direct their attention to «5, to what we do, and so 

 form associations connected with acts of ours. 



Having finished our attempt to give a true description of the 

 facts of association, so far as observed from the outside, we may 

 now progress to discuss its inner nature. A little preface about 

 certain verbal usages is necessary before doing so. Through- 

 out I shall use the word ' animal ' or ' animals,' and the reader 

 might fancy that I took it for granted that the associative pro- 

 cesses were the same in all animals as in these cats and dogs of 

 mine. Really, I claim for my animal psychology only that it 

 is the psychology of just these particular animals. What this 



