58 



.JOHN B. WATSON 



Secondly, the ease with which complications can be intro- 

 duced makes the maze very desirable. This is brought about 

 by the flexibility in the arrangement of the entrances and radial 

 stops. Fig. 1 shows the maze just as it was used by Miss Hubbert 

 in the work which she reports on page 60. 



The camera lucida attachment is easily installed; it is simple 

 and permanent. Had it not been for Professor Yerkes' insis- 

 tence upon the necessity for having some recording device for 

 the movements of the animals, it is doubtful if this attachment 

 would have been made in its present form. He suggested to me 

 two years ago that some such device would be desirable and that 

 he had certain plans for its construction. Before the publica- 

 tion of his work it became necessary to have an exact record of 



Figure 2. Chartometer 



the stages of the acquisition of the maze habit, since Miss Hubbert 

 wished to undertake a comprehensive study of the difference in 

 the acquisition of habits of animals of different ages. Accord- 

 ingly, I went ahead independently and finally constructed the 

 apparatus which is shown in Fig. 1 . 



A large plate glass mirror (Mj, 91 cm. wide by 121 cm. in 

 length, was placed at an angle of 45° directly over the center of 

 the maze. This mirror was strapped by small clamps to the 

 edge of the supporting framework. At a certain distance from 

 this mirror a second mirror (M), 60 cm. by 75 cm., is placed at 

 an angle of 45 ° above the maze and at such a distance from M x 

 that the light reflected downward from M falls outside of the 

 maze. Below M, and in the path of the light reflected from it, 

 is placed a single achromat (L), 6 cm. in diameter and 50 cm. 

 focus. The lens is placed in a barrel and the barrel is attached 

 to a wooden disc 30 cm. in diameter. This board is attached 



