MENTAL HORIZON 105 



tendency. Mentally the chimpanzee occupies a high plane 

 within his own sphere of life, but within those limits the 

 faculties of the mind are not called into frequent exercise 

 and, therefore, they are not so active as they are in man. 



It is difficult to compare the mental status of the ape 

 to that of man, because there is no common basis upon 

 which the two rest. Their modes of life are so unlike as 

 to afford no common unit of measure. Their faculties are 

 developed along different lines. The two have but few 

 problems in common to solve. While the scope of the 

 human mind is vastly wider than that of the ape, it does 

 not follow that it can act in all things with more pre- 

 cision. There are, perhaps, instances in w r hich the mind 

 of the ape excels that of man by reason of its adaptation 

 to certain conditions. It is not a safe and infallible guide 

 to measure all things by the standard of man's opinion of 

 himself. It is quite true that, by such a unit of measure, 

 the comparison is much in favor of man ; but the conclu- 

 sion is neither just nor adequate. It is a problem of great 

 interest, however, to compare them in this manner, and the 

 result indicates that a fair specimen of adult ape is in about 

 the same mental horizon as a child of one year old. But 

 if the operation were reversed and man were placed under 

 the natural conditions of the ape, the comparison- would 

 prove much less in favor of man. There is no common 

 mental unit between them. 



On problems that concern his own comfort or safety the 

 chimpanzee exercises the faculty of reason with a fair 

 degree of precision. He is quick to interpret motives or 

 to discern intents, and he is a rare judge of character. He 



