206 ROBERT M. YERKES AND CHARLES A. COBURN 



with problem 1. It would then appear to be from four to eight 

 times as difficult as the latter. 



One important aspect of the experiment should be here con- 

 sidered. According to our procedure, one of the pigs led and 

 the other followed in a series of trials. It was therefore possible 

 that the follower might be aided in its choice either by watching 

 its companion or by the odor of the box in which the animal 

 fed. There can be no doubt of the tendency of the pigs both to 

 watch one another and to be influenced by the odor of the 

 boxes, but that the solution of the problems did not depend 

 upon either of these factors, although the number of trials 

 necessary to solution may have been modified thereby, is proved 

 by the fact that both subjects made ninety per cent of correct 

 choices when leading. 



PROBLEM 3 



All of the data in connection with this problem are to be 

 found in tables 6, 7, and 8. The problem is definable as alter- 

 nately the first mechanism at the right and the first at the left. 

 At the beginning of work on this problem, the animals were 

 given their trials alternately as in the preceding problems, but a 

 strong tendency to follow manifested itself, and on the second 

 day the trials were given by pairs. That is, each individual 

 was allowed to choose in succession the first door at its right 

 and the first door at its left, and was then required to wait while 

 its companion responded to the same pair of settings. Thus, 

 following was rendered impossible. 



The tendency to choose the second door from the left natur- 

 ally manifested itself in .the early work on this problem, but it 

 was soon destroyed by training, and the course of experimen- 

 tation proceeded smoothly to the perfect solution of the problem. 



It is to be noted that from the first, ten trials constituted a 

 series. Because of the familiarity with the general experimental 

 situation which the animals had acquired and the experience of 

 the experimenters in the control of hunger and punishment, 

 it was easier to obtain reactions to ten successive trials at this 

 time in the investigation than to five early in the work, with 

 problems 1 or 2. 



The female succeeded in solving problem 3 as the result of 

 420 trials; the male, as the result of 470. 



