INSTINCTS AND HABITS IN CHICKS 71 



trained to avoid was presented in combination with a new 

 color, the chick continued its specific avoiding reaction regard- 

 less of the relative brightness values of the stimuli, demands, 

 I believe, that color quality as well as intensity be assumed as 

 a determining factor in the reactions of these chicks. 



F. The Persistence of Modifications 



Hints of the material about to be presented have necessarily 

 been dropped in the discussion of previous topics. Yerkes ^ 

 publishes in his work on the dancing mouse a valuable table 

 of results on " Measurements of the Duration of a Habit." 

 Commenting on this data, he says, "It is safe, therefore, to 

 conclude from the results which have been obtained that a 

 white-black or black-white discrimination habit may persist 

 during an interval of from two to eight weeks of disuse, but that 

 such a habit is seldom perfect after more than four weeks." 

 If one should assume that the chicks depended upon the element 

 of brightness only, the results obtained for them in our black- 

 blue tests would be comparable with the black-white and white- 

 black records of the mice, provided one allowed for age differ- 

 ences, as well as for the fact that the discrimination, assuming 

 the human standard, was made more difiicult for the chicks on 

 account of the smaller difference in the brightness of the two 

 stimuli. 



The chicks in these tests (see table 25) were placed in the 

 entrance box in the manner followed in the original experiments 

 and allowed to escape from the apparatus to the cage. The 

 cards were exchanged after each trial, that is, regularly alter- 

 nated right and left. No shock was given and both exits remained 

 open throughout. There was a noticeable difference in the 

 behavior of the chicks in the apparatus after the interval. 

 Instead of smoothly going to work they usuall}^ hesitated a 

 few moments and craned their necks about before starting for 

 an opening. The same kind of phenomenon was noticeable, 

 ordinarily, in the behavior of a previously trained chick when 

 lifted in the hand after an interval of some weeks during which 

 it had not been handled. Whereas the animal had come to 

 submit freely and without struggle in the course of the original 

 training, now, when grasped over the back, it sometimes kicked, 



1 Yerkes, R. M.: Op. cit., p. 256. 



