GRAPHIC METHOD OF RECORDING MAZE-REACTIONS 53 



is likely to prove most practicable where two rooms, the one 

 above the other, are available for maze experiments. The 

 writers have tested the method only with very small mazes. 



II. The single reflection method. The device for this method, 

 as shown in Figure 1, II, consists of a mirror, M, which is placed 

 above the maze, Z, and which causes an image of the maze to 

 fall upon the lens, L. This image is focused upon a record sheet 

 at D. As in the case of the direct method, the drawing board is 

 hooded in order that the experimenter may work in dim light 

 and thus be able to see, clearly, both the alleys of the maze and 

 the moving animal. In comparison with the former method, 

 this is somewhat more expensive. It yields a completely re- 

 versed image and it may be used for even very large mazes. Its 

 chief defects are the inconvenient inclination of the drawing 

 surface, at one end of which the observer must work. In this 

 laboratory we have thoroughly tested the method and find it 

 to work satisfactorily. A little practice enables the observer to 

 follow a rapidly moving rat or mouse and to obtain records 

 which yield accurate measurements of distance, time and errors, 

 even in the early experiments with a given subject. 



III. The double reflection method of Watson (camera lucida 

 method). Two mirrors are used in this apparatus together with 

 a lens and drawing board. The arrangement of these parts is 

 shown in Fig. 1, III. This apparatus has the disadvantage of 

 being more expensive by reason of an additional mirror than the 

 preceding method, and it is also placed at a slight disadvantage 

 because it supplies an image of the maze which is reversed from 

 right to left. To counterbalance these disadvantages, we may 

 mention the following obvious advantages: (1) the more con- 

 venient position of the drawing surface; (2) the removal of the 

 experimenter to a considerable distance from the maze; and (3) 

 the adaptability of the apparatus to spatial demands in room or 

 laboratory. 



A more detailed account of this method is given by Professor 

 Watson on p. 58. 



IV. The double reflection method of Kellogg. This differs 

 from method III in that M 2 is placed below the lens, and the 

 image falls upon the record sheet from below, as in method I. 

 Disturbing shadows cast by the hand of the experimenter are 

 thus avoided. The image obtained by this method is completely 



