LIGHT DISCRIMINATION IN THE ENGLISH SPARROW 101 



shocked they very soon learned to turn and go around to the 

 other light. They were slower to learn to enter the alleyways 

 because they were dark and the bird avoids dark places. But 

 even this natural tendency was overcome in a surprisingly 

 short time. 



The directness or indirectness of approach and entrance into 

 the discrimination box varied in the different cases. Two of 

 the birds would hesitate several seconds or even minutes before 

 entering the discrimination box. But the other two seemed 

 eager to go through the experiment. Male IV was calm and 

 deliberate in his movements. He would hop into the doorway 

 (Di, Fig. 1) as soon as it was opened. He would sit in the door- 

 way or just outside for several seconds, turning his head quickly 

 to one side or the other. (All the birds looked at the lights 

 with their heads turned to one side or the other. They never 

 seemed to look at the lights with both eyes at the same time.) 

 Then he would hop calmly on, to whichever light he had chosen. 

 He never seemed excited and seldom required shocking. When 

 shocked it required a heavy discharge to produce any effect. 



Male V was always very much excited. For a long time he 

 would dart out to one side or the other without attempting to 

 discriminate the lights. Suddenly he changed his method and 

 would hesitate a long time just beyond the door (D, Fig. 1). 

 There he would sit, often for several minutes. Sometimes the 

 observer would have to shock him before he would move. But 

 usually after a long hesitation he would dart on to one light 

 or the other. The observer felt that as a usual thing he did 

 not rely upon visual discrimination. His judgments were never 

 very satisfactory. 



At the beginning of the experiment Female V would always 

 hesitate in the doorway, discriminate between the lights and 

 hop on. But later she acquired the habit of darting out to one 

 light or the other the very instant the door was opened. For 

 a long time it seemed absolutely impossible to break up this 

 habit. Frequently there would be days when the bird seemed 

 to show some improvement but in general she gave very poor 

 results. Finally the observer decided that she did not have such 

 good sight as the other birds and that she had really reached 

 her threshold of discrimination. The difference in the intensity 

 of the lights was increased a little and after a short time the 



