INSTINCTS AND HABITS IN CHICKS 39 



Of course these averages hide the unusual performances of 

 individuals. Chick no. 72, for instance, missed only once out of 

 fifty reactions on its second day, on the fifth day it struck, 

 seized, and swallowed forty-eight grains in fifty trials, and on 

 the eighth day devoured every one of the fifty without a slip. 

 The complete record of this animal is given in table 5. A com- 

 parison of its record with that of no. 70 brings out nicely the 

 point of individual differences in accuracy. No. 72 developed 

 more rapidly than no. 70, and also attained a much higher aver- 

 age degree of efficiency. The records of both chicks are con- 

 sistent throughout. They bespeak a more finely adjusted mechan- 

 ism in the one case than in the other. If we were seeking points 

 of difference instead of identity in this investigation, we should 

 dwell more at length on variations in other respects. Chicks, 

 as one might expect, differ definitely and consistently from 

 day to day in the accuracy of their reactions, in the rapidity of 

 their movements, in their food preferences, and the like, much 

 as men do. 



To return to fig. 7. The curve representing the course of 

 development of the complete co-ordination, Curve IV, reaches 

 its highest elevation during the twenty-four days at 42.5 on a 

 scale of 50. Each of these curves is intended to represent an 

 aspect of the pecking of the chicks under the conditions described. 

 Whether or not the reactions in the litter were more accurate 

 than those on the harder cardboard, I cannot say, not having 

 made any measurements. To be sure, the long periods of prac- 

 tice were spent in pecking under conditions quite different from 

 those that obtained in the tests. 



It has been the aim of this investigation to discover the mean- 

 ing that should attach to such expressions as the accuracy, the 

 perfection, or the congenital definiteness of the instinctive action 

 that has been generally considered one of the most perfect, 

 namely, the pecking reaction of chicks. Morgan and Thorndike 

 are correct in asserting that this reaction is imperfect at birth — 

 not " very nearly " perfect as Morgan thinks, but very imperfect. 

 But Thorndike ' doubts the fact of improvement. "As a matter 

 of fact," he writes, " the pecking reaction may be as perfect at 

 birth as it is after 10 or 12 days' experience." I shall have to 



^Thorndike, E. L.: The instinctive reaction of young chicks. Psych. Rev., 1899, 

 vol. VI, p. 285. 



