8 K. S. LASHLEY 



Control experiments indicated that the red was below the chick's 

 threshold and that he was reacting to it as to darkness. The 

 intensity of the lights was next increased to 1 /45 of the standard 

 and Chick A was offered a choice of them. He chose — 



Furthermore, when offered a choice between the red and dark- 

 ness he chose the red in 8 of 10 trials showing that the red was 

 above his threshold. At low intensities the green has a much 

 greater stimulating value than the red for the dark adapted 

 chick. 



c. With the energies of the beams at 1/90 standard, Chick 

 A. light adapted, was introduced into the discrimination box. 

 He chose — 



Green Red 



10 



100% 0% 



As a control he was offered a choice between the red and dark- 

 ness. He chose the red in 10 consecutive trials. The red used 

 was below the threshold of the experimenter when light adapted 

 and a record of the time of adaptation of the experimenter and 

 the time of reaction of the chick shows that the chick also re- 

 quired a slight darkness adaptation before the red became 

 visible to him. His accurate choice of the green at this energy 

 was undoubtedly due to the fact that the choice was made 

 before the red came above threshold. 



d. The energies of the beams were increased to 1/9 of the 

 standard. Chick A, dark adapted for one hour, chose — 



Green Red 



5 5 



50% 50% 



The energies were immediately #educed to 1/18 and he chose — 



Green Red 



3 3 



50% 50% 



Under the same conditions Chick C chose — 



Green Red 



4 6 

 40% 60% 



When the energy is as great as 1/18 of the Pfund standard 



