192 CHARLES A. COBURN 



TABLE 1 



Intensity Discrimination 



Correct choices 

 Date No. of tests Crow No. 1 Crow No. 2 • 



Conditions of Discrimination 



Cardboard and opal flashed glass — Opal flashed glass 

 July 19 5 5 5 



" 19 5 4 5 



" 20 5 5 5 



Two milk glasses and opal flashed glass — Opal flashed glass 

 July 21 5 5 5 



" 21 5 5 5 



"22 5 4 5 



One milk glass and opal flashed glass — Opal flashed glass 



5 5 2 



5 3 3 



5 4 4 



5 4 4 



5 5 4 



5 3 4 



5 4 5 



5 5 5 



5 4 5 



5 5 5 



5 5 4 



One sheet of paper and opal flashed glass — Opal flashed glass 



July 29 5 4 3 



" 30 5 5 3 



" 30 5 5 3 



" 31 5 5 3 



" 31 5 5 4 



Aug. 15 5 4 



"15 5 5 



These results are but roughly indicative of the crows' ability 

 to distinguish differences in illumination. Accurate measure- 

 ments of the birds' visual acuity was not the aim of our ex- 

 periments. 



The chief value of these experiments on the discrimination of 

 intensity is the demonstration of the ease with which the crow 

 is able to adapt itself to experimental conditions and to solve 

 accurately one variety of problem. 



With the beginning of the experiments on size discrimination, 

 the apparatus was so shifted that the front end was immediately 

 before a large south window. In this position it remained dur- 

 ing the season. The only other change was the insertion of the 



