Yerkes and Dodson, Habit Formation. 



461 



which could be completed by the experimenter, by closing the key 

 K^ whenever the feet of a mouse rested upon any two adjacent 

 wires in either of the boxes. In this circuit were an electric 

 battery and a Porter inductorium. One of these electric boxes 

 bore black cards, and the other white cards similarly arranged. 

 Each box bore two cards. One was at the entrance on the out- 



TABLE I. 



Positions of white cardboards for two preference series and twenty-five training 



series. 



side of the box and the other on the inside, as fig. i indicates. 

 The latter consisted of three sections of which two constituted 

 linings for the sides of the box and the third a cover for a portion 

 of the open top of the box. In no case did these inside cards 

 extend the entire length of the electric boxes. The white and black 

 cards were readily interchangeable, and they never were left on 

 the same electric box for more than four consecutive tests. The 



