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 in ver" 
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, in 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 in 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 
