HABIT FORMATION IN FROGS 329 



instinct. It is quite evident therefore that if Yerkes based his 

 conclusions solely upon the results of his experiments described 

 in the paper from which the quotations are taken, such conclu- 

 sion is made untenable by my results; but if Yerkes had in 

 mind also the frog's position in the animal scale as compared 

 with the other vertebrates whose behavior is known, as he doubt- 

 less did, then it is possible that his conclusion is not far from 

 the true one. The fact that our results warrant us to estimate 

 the rate of habit formation so differently is sufficient evidence 

 that we are not at present in possession of sufficient experi- 

 mental data to enable us to say with any degree of precision 

 what rate of learning by experience is representative of the green 

 frog. 



The fact that habit formation may be very rapid while a cer- 

 tain instinct is being exercised, and very slow when another 

 instinct in the same animal is exercised, makes it doubtful 

 whether the placing of an animal in a scale of intelligence is 

 of much scientific value if only a part of the animal's behavior 

 is known. Thus the frog might be placed among the least 

 intelligent of animals upon the basis of Yerkes' experiments, 

 but if my results serve as a basis, then the frog might stand 

 above the raccoon (4), the squirrel (12), the rat (3), the cat (i), 

 and perhaps the dog (5), in all cases judging merely by the 

 number of trials necessary to perfect a habit. It is clear then, 

 that we are not in a position to classify an animal in the scale 

 of intelligence from observations on its behavior in which only 

 one or two specialized neuro-muscular mechanisms arc involved ; 

 on the contrary, s^^stematic classification cannot be considered 

 accurate until all or nearly all the more or less specialized neuro- 

 muscular mechanisms have been investigated. 



In comparing the rapidity of habit formation of Yerkes' 

 frogs in the labyrinth with that of mine while feeding, it may 

 be objected that a conclusion derived from such a comparison 

 is not fraught with as much meaning as might appear at first 

 sight, since Yerkes' frogs may be thought of as having acquired 

 a habit of doing a new act — one added on — a positive habit; 

 while my frogs learned not to do an act that they instinctively 

 incline to do, a discontinuance of a habit or instinct already 

 present — or a positive habit. This would mean that we are 

 comparing processes which differ from each other, not in de- 



