LIGHT DISCRIMINATION IN THE ENGLISH SPARROW 



89 



readings taken on June 1, 1912, which was during the time that 

 the birds were making the most difficult discrimination. 



TABLE II 



The figures in the first column indicate the number of discriminations required. 

 The second column shows the c. p. of the standard light, calculated in Hefner units 

 which remained the same throughout the experiment. The third column indicates 

 the c. p. of the variable light and the last column shows the difference in intensity 

 between the standard and variable. 



III. RESULTS 



(1) Threshold for discrimination. — Table III shows the four 

 sparrows' threshold of discrimination for the standard intensity 

 .098. The second column gives the least difference between the 

 intensities of the standard and the variable illuminated areas 



TABLE III 

 Showing the threshold of brightness discrimination for each of the four birds. 



