THE DEVELOPMENT OF AN INSTINCT 



281 



practice, followed by a gradual and fairly steady improvement 

 thereafter. It seems to the writers that a given amount of 

 practice, quite constant for the different groups, is necessary 

 to smooth the way for the operation of a native capacity whose 

 efficiency is largely a function of the age of the animal. In 

 other words, it is our view that the second portion of the curves 

 is almost entirely a record of maturation. If this be true, and 

 further experimentation can no doubt establish the truth or 

 falsity of this conjecture, there would seem now to be some 

 explanation for the negative results obtained in previous tests 



TRIALS 

 50 



45 

 40 

 35 

 30 

 25 

 20 

 15 

 10 

 5 



DAY5 



Figure 2. — Curves showing rate of improvement in accuracy of the pecking in- 

 stinct during the first twenty-four hours after five days' artificial delay. V x , 

 curve for nos. 22 and 24; V 2 , curve for nos. 23 and 27. S, standard curve 

 reproduced for comparison. Data in table 2. 



of the effect of social influence on the development of this 

 instinct. 



The effect of the first day's practice after an artificial delay 

 of five days from the time of hatching is indicated in curves 

 Vj and V 2 , figure 2. The records first given show the degree of 

 accuracy in the first 50 trials — characteristically low. It will be 

 noticed that as practice proceeded the improvement was both 

 rapid and regular. Twenty-four hours from the time practice 

 was started the individuals of these two sub-groups reached an 



