100 EUPHA FOLEY TUGMAN 



and after 240 trials he succeeded in giving 30 correct choices. 

 The observer felt that the bird could discriminate the areas 

 when the difference in intensity was .013 c.p. But when he was 

 on the .009 intensity he acquired the position habit which lasted 

 through the 306 trials at the next position and almost until the 

 end of the investigation. 



Figure 4 represents the results of Male V and Female VI. 

 The curves are more irregular than those for Male IV and Female 

 V. The curve of Female VI is more nearly like those of Male 

 IV and Female V than is the curve of Male V. The sudden drop 

 in both curves indicates the fact that both birds learned to choose 

 the darker of the two illuminated areas. After Female VI 

 learned the first discrimination she had no trouble until the 

 difference in intensity became small. She readily discriminated 

 a difference in intensity of .022 c.p., but when the difference 

 was reduced to .017 c.p. she was incapable of discriminating the 

 areas even after 720 trials. The difference in intensity was then 

 increased to .022 c.p. and after 450 trials she succeeded in dis- 

 criminating the lights. 



Male V learned to go to the darker of the two illuminated 

 areas more quickly than did Female VI, but his other results 

 were never so good as those of Female VI. The observer felt 

 that the discrimination was really not difficult for the bird but 

 that many of his wrong choices were due to fright. He often 

 did not even attempt to discriminate the lights. He would go 

 to one light and if he failed, would hurry around to the other 

 side and into the alley way. He was beginning to give better 

 results when he died. 



(3) Incidental results. — The author has included under this 

 heading some of the most interesting facts brought to light 

 during the experiment with the birds. 



(a) Individuality. As shown in the previous discussion, the 

 sparrows exhibited distinct individual differences in their rate of 

 learning. This was also true of their general behavior and of 

 their method of attacking the problem. The individual birds 

 also varied their course of procedure at intervals during the 

 experiment. 



All the birds were quick in learning the apparatus and its 

 various alleyways. When they chose the wrong light and were 



