RESPONSES TO MONOCHROMATIC LIGHT 5 



green. Further control experiments to determine the nature of 

 the effective stimulus were then undertaken. 



June 5th. Eight normal trials were first given. 100% cor- 

 rect. Then red beam was cut out ; green left at full intensity. 

 Went to red side (darkness) on every trial (10 trials). 



June 6th. Eight normal trials. ioo% correct. Then green 

 was cut out and red left at full intensity. Right position habit 

 developed immediately. Discrimination lost. Then 4 normal 

 trials were given. 100% correct. 



June yth. Eight normal trials. 100% correct. Green out, 

 red at full intensity. 14 trials given. Right position habit devel- 

 oped immediately. 4 normal trials were then given. 100% 

 correct. 



June 10th. Eight normal trials given. 100% correct. Red 

 cut out; green full intensity. Went to red side (darkness) on 

 all 15 trials. 2 normal trials were next given. Both correct. 



June nth. Six normal trials given. 100% correct. Green 

 out ; red full intensity. Left position habit developed imme- 

 diately. (9 trials.) Then 10 normal trials were given. 90% 

 correct. 



June 12th. Six normal trials given. 100% correct. Both 

 lights cut out for 15 trials. Right position habit developed. 4 

 normal trials were given. 100% correct. 5 



The detailed experiments upon the rabbit are not given. 

 They are identical in character and number with those given 

 the rat. The results are exactly the same except that in the 

 case of the rabbit a decrease of 50% in intensity of the green 

 produced disturbance. The work of Washburn and Abbott on 

 the rabbit, showing the lack of stimulation by red, had not 

 appeared when our work was completed. Our results are in 

 complete harmony with respect to red. 



These results seem to show perfectly that the green was the 

 effective stimulus and that the red had no stimulating value 

 whatsoever. The animals were avoiding a lighted compartment. 

 One might decrease the intensity of the green light enormously 

 and eliminate the red altogether without changing the accuracy 

 of the responses. When, however, the intensity of the green 



5 In all of the control experiments food might be had regardless of stimulus 

 light reacted to. Food was always kept in both compartments even during the 

 training series. 



