MENTAL LIFE OF APES AND MONKEYS 261 



It is probable that further study may reveal in the anthro- 

 poid apes a higher psychic development than is found among 

 the smaller members of the monkey tribe from which has 

 been derived most of our knowledge of the simian mind. 

 Our account therefore will have to do mainly with the smaller 

 species which are more commonly and easily kept in captivity 

 and which are more distantly related to the human family. 



Thorndike has performed several series of experiments 

 with three Cebus monkeys by placing food in boxes which 

 could be opened by working one or more mechanical 

 devices. The times taken by the monkeys in learning how 

 to open the boxes were recorded, and it was found that 

 associations were formed much more quickly than hi cats, 

 dogs and chicks. "Whereas the latter," says Thorndike, 

 "were practically unanimous save in the cases of the very 

 easiest performances, in showing a process of gradual 

 learning by a gradual elimination of unsuccessful movements, 

 and a gradual reinforcement of the successful one, these are 

 unanimous, save in the very hardest, hi showing a process of 

 sudden acquisition by a rapid, often apparently instanta- 

 neous, abandonment of the unsuccessful movements and a 

 selection of the appropriate one which rivals hi suddenness 

 the selections made by human beings in similar performances." 

 This fact, according to Thorndike, does not show that 

 monkeys reason or even have ideas. Their greater clearness 

 of vision, the greater number and precision of their move- 

 ments, and their greater curiosity are factors which, aside 

 from the superior development of their brains, give the 

 monkeys an advantage over cats and dogs, in acquiring new 

 associations. The monkey mind shows an advance over 

 that of the lower mammals in the greater number, delicacy, 

 complexity and permanence of its associations, and the 

 readiness with which associations are formed, but in their 



