l66 EVOLUTION: THE AGES AND TOMORROW 



chips and brass slugs were given to the chimps. The brass 

 slugs could be dropped into the slot but no grape was de- 

 livered, and in a matter of a few days the six apes were well 

 aware of this and left them strictly alone. Every time a mix- 

 ture of chips and slugs was tossed into the cage there was a 

 mad scramble for the chips, but once the chimps learned 

 that slugs would not deliver a grape they never again 

 touched them. 



Children at about the four-year level or less adapt easily 

 to the importance of money but do not at first diif erentiate 

 the relative values of coins. Wolfe was interested in finding 

 out whether the mentality of the ape was equal to the task 

 of dealing with coins of different value. His apes had al- 

 ready made a sharp distinction between white poker chips 

 and brass slugs, so he now introduced a blue chip which, 

 when placed in the slot of the Chimp-O-Mat, delivered two 

 grapes. In time the chimpanzees seemed to realize the differ- 

 ence, for they would take the blue with twice the buying 

 power in preference to the white, which certainly is a proc- 

 ess of "thinking." 



Wolfe also wondered whether his charges could be made 

 to work for the "chimp money." Accordingly he intro- 

 duced a Work Machine, a device consisting of a pump 

 handle which lifted weights. At the start of this experiment 

 when the ape worked the handle, a grape was delivered into 

 a cup. All the experimental animals quite willingly worked 

 the handle even though it involved lifting heavy weights. As 

 soon as they were familiar with the operation of the ma- 

 chine, poker chips were substituted. After a slight uncer- 

 tainty they began to work just as willingly for the chips as 

 for the direct reward of a grape. When brass slugs were 

 substituted, they would not "work"; it was either work for 

 pay or not at all. These chimpanzees would even work the 

 machine for chips at times when the "money" could not be 

 spent, but would make impatient demands eventually if the 

 delay was too prolonged. 



