FUNCTION OF VIBRISSAE IN BEHAVIOR OF WHITE RAT 71 



which we appeal and in a certain degree it is true of the contact 

 senses but the behavior involved in the latter reveals much 

 more to us. In these experiments, for example, nothing could 

 be said with certainty as to how much or what the animal saw, 

 but every movement which was made, every part of the box 

 which was nosed, could be described. It cannot be known in 

 any way when an animal begins to sense differences in color or 

 brightness but it was always possible to see when these animals 

 began to seek contact experiences in definite places. Nothing 

 can be said as to whether any process of compar son goes on 

 when an animal is in the presence of two colors but when it 

 goes from one lamway to another trying the sides of both, when 

 it cannot choose a coriTigated pathway until it has tested a 

 plain one, it may be inferred that something like comparison, 

 something like discrimination is present. So far as behavior can 

 show the whole process is open in the use of the tactile senses 

 but when the distance senses are used we see as a rule only the 

 consummatory reaction and the developing of the same, the 

 perfecting of a citide reaction is hidden. 



This is a plea for more experimentation involving the cuta- 

 neous senses and a protest against the conclusiveness of the 

 analyses of the mental processes of animals when based upon 

 investigations which require the use of the weakest and most 

 defective sens-e. 



There are rather constant differences between discriminations 

 involving the distance senses, particularly vision, and those 

 which are made through the contact senses. In the one the 

 stimulus must be presented and in the other it must be 

 actively sought. There "is therefore a greater degree of activity 

 in the one case than the other. The greater self activity thus 

 aroused in the animal is probably a factor in favor of this latter 

 form of discrimination. In the experimental work emploAdng 

 vision, the colors, forms, etc., to be discriminated have usually 

 been presented simultaneously, or if successively, with only a 

 very brief interval between. When the contact senses are used 

 the sensory cues are of necessity successive and therefore time 

 and place are greater factors in this form. If there is any com- 

 parison in the case of simultaneous visual presentation it may 

 be made directly, at least the eP'ect of contrast is direct; but in 

 tactile discrimination some form of mental content must be 



