l6 Journal of Comparative Neurology and Psychology. 



Method of Presenting the Stimuli. 



The animals were carried from their living room to the dark- 

 room, and allowed to remain there for two or three minutes. A 

 malaga grape was then placed in the food-box at the base of the 

 colored band selected as the positive color. The animal was next 

 permitted to climb to mj shoulder. The screen was then raised 

 and the animal allowed to walk towards the lights (for a distance 

 of three feet) and make his choice, i. e., open either of the two boxes. 

 If the red box were opened, the grape could be obtained; if the 

 green, the animal was pulled back to my shoulder. After the choice 

 had been made, the screen was again dropped over the lights and the 

 animal allowed to finish eating the grape. 



At first, the stimulations were given at intervals of three minutes, 

 but the animals became so eager and restless during the long wait, 

 that the tests were finally given as rapidly as the apparatus could 

 be arranged. The animal was always j^ermitted to finish eating the 

 food obtained at the previous trial before the next test was given. 



Differences between the olfactory values of the two boxes were 

 eliminated in a variety of ways: The boxes were frequently inter- 

 changed ; other similar, boxes were used occasionally ; food was placed 

 in both boxes, but the conditions were so arranged that the animals 

 could get food only in the one box. Fig. 4 shows one of the boxes. 

 A horizontal wire partition runs across the box, 1" from the top. 

 When the grape was placed below this, the monkey never made 

 the slightest effort to get it. The most important control test was 

 made after the association had been firmly established by allowing 

 one or two grapes to lie very near the box kept with the green, or 

 with the yellow as the case might be (the color to which the animal 

 was not reacting positively). In no case were these grapes ever 

 disturbed — even if the animal made an occasional error and opened 

 the wrong box, he never seemed to notice that the grapes were 

 nearby. In the hundreds of cases where he had obtained the grapes, 

 he had found them in the top compartment of the box after he had 

 pulled open the lid. While these tests do not appear in the tabulated 

 report, they were made exhaustive. In addition to controlling the 

 factor of smell, such tests tend to show conclusively that possible 



