78 CHARLES A. COBURN AND ROBERT M. YERKES 



may vary in number from two to twelve (this was the original 

 form of apparatus). Some one key, in any group of keys pre- 

 sented, when pressed will cause a bell to ring, thus indicating, 

 success. Without other aid than his own observation, the subject 

 is expected, from repeated presentations of the keys, to discover 

 the essential relation and to acquire the ability to select the 

 right key with certainty. 



This method has the advantage of enabling the experimenter 

 to present increasingly difficult problems to his subjects. It 

 has further the advantage of enabling him conveniently to record 

 the essential features of reaction, and later to analyze the reactions 

 at his leisure. But most important of all, it yields strictly 

 comparable results when applied to widely differing organisms. 

 Naturally, although the same problems may be presented to 

 diverse types of organism, the reaction mechanisms must be 

 suited to the subject in question. 



Without further general comment or discussion of the multiple 

 choice method, we shall describe the form of apparatus and 

 procedure employed with the crow. 



APPARATUS AND METHOD 



In the accompanying plate, designated as figure 1, and in 

 the ground plan of the observation-room and apparatus, shown 

 in figure 2, the general experimental situation is represented. 

 Figure 1 shows in the background the building which was used 

 both as a shelter for the crows and as an observation place for 

 the experimenter. To this building is attached a fly which 

 appears in C, D, and E of Figure 1. In figure 2, the ground 

 plan of the building, are seen the experimenter's room, A, and 

 the crow room, B, the latter containing a perch, P. All coarsely 

 dotted lines in this figure indicate walls or partitions made of 

 poultry wire. The large fly was, for the purposes of our ex- 

 periment, divided into two parts by a wire partition. In the 

 smaller of these portions, shown at the right of figure 2, the 

 multiple choice apparatus was located. The crows could enter 

 this portion of the fly only at the will of the experimenter, where- 

 as they were allowed the freedom of the larger portion, which 

 we have labelled C. As figure 2 is drawn to scale (one inch to 

 forty-eight) it is unnecessary to give the measurements of the 



