Modification by Experience 257 



that memory ideas connected with immediately preceding 

 peripheral stimulation may occur in the raccoon's mind. 



89. Inhibition involving Discrimination of Simultaneous 



Stimuli 



Experiments of the second class, where the different stimuli 

 are simultaneously presented, have been made by Kinnaman 

 on monkeys, by Cole on raccoons, by Porter and Rouse on 

 birds, and by Yerkes on the dancing mouse. Kinnaman's 

 Macacus monkeys entirely failed to discriminate cards with 

 different figures on them when one card was placed on a box 

 with food and the other on an empty box (221). The English 

 sparrow and the cowbird, on the other hand, both learned to 

 do this. Monkeys and birds alike learned to discriminate 

 glasses covered with differently colored papers, and the posi- 

 tion or number of a vessel in a series (221, 345, 371). Cole's 

 raccoons learned to discriminate a black from a white glass, 

 and, with more difficulty, a red from a green one (82). The 

 monkeys were able to distinguish fairly well differences in 

 size, and in the form of the vessel. The birds were not 

 tested with size differences, and Porter's birds failed to 

 discriminate the vessel forms; Porter suggests that the 

 monkeys may have been helped by the fact that the 

 vessels Kinnaman used differed in size as well as in form. 

 Rouse found that his pigeons did tolerably well in learning 

 form differences (371). Our own experiments with the chub, 

 where the red and green forks were presented together and the 

 fish learned rather quickly to bite at the red rather than the 

 green even when both were empty (421), also illustrate this 

 method, as does the case of the chick stung by the bee, who, 

 on the basis of this experience, pecks at other insects but 

 V avoids bees (281). Similarly, Forel's bees and wasps, which 

 were trained to pick out pieces of paper of particular colors 



