234 THE INTELLIGENCE OF MAMMALS 



involved in most animal performances is a matter of much 

 difficulty. We may be guided on the one hand by analogy 

 with ourselves, which leads us to infer that actions similar 

 to our own are accompanied by similar mental states; and 

 by the law of parsimony on the other, which forbids us to 

 assume the existence of higher mental qualities if the phe- 

 nomena can be explained in terms of simpler mental pro- 

 cesses. In the imperfect state of our knowledge these two 

 guides often lead to opposed conclusions. If we applied the 

 principle of Morgan to the psychology of our fellow human 

 beings we should be continually led astray. So in our inter- 

 pretations of the psychology of the higher animals we may 

 very frequently be "missing it" more or less widely in our 

 adherence to this principle. The antecedent probability 

 in favor of not giving the animal the benefit of the doubt 

 diminishes as we ascend the scale of psychic life. We may 

 suspect that our interpretations "fall short/' but our opin- 

 ions cannot be said to rest on a secure basis until we are 

 able to support them by experimental proof. The principle 

 of Morgan affords a check to the natural tendency to "an- 

 thropomorphism " which is a common human failing; it 

 throws the burden of proof on whomsoever attempts to es- 

 tablish the existence in animals of higher faculties, and if 

 the positive conclusions to which it permits us to come fall 

 short of the truth we can at least rely on them so far as 

 they go. 



As a typical instance of the workings of the animal mind 

 we may cite the performances of Professor Lloyd Morgan's 

 dog, Toby, which had learned how to open a gate that led 

 out of his master's yard. The gate was fastened by a latch, 

 but swung open by itself if the latch was raised. Whenever 

 the dog desired to make his escape he put his head between 

 the bars, lifted the latch and went out. Such an act 1 might 



