PATTERN-DISCRIMINATION IN VERTEBRATES 



361 



I do not wish to be understood as presenting these results 

 as data fit for strict comparison with the results obtained by 

 the discrimination method. The attitude of the observer is 

 different in the two cases, and the problem is also different. 

 However, we may justly conclude from them that the visual acuity 

 of Monkey 2 is of the same order as that of the well trained 

 human observer under similar stimulus-conditions; while the 

 former showed a visual acuity on the order of four times as great 

 as that shown by the chicks. Closer comparisons are not 

 warranted. 



SUMMARY 



Definite positive results were not obtained in the tests made 

 on the dog. All his behavior is consistent with the hypothesis 

 that he is insensitive to differences of detail in visual objects. 

 The results are not definite enough to warrant such conclusion, 

 however. 



The visual acuity of the monkey compares favorably with 

 that of the human subject under similar conditions. 



The visual acuity of the chicks appears to be not over one- 

 fourth that of the monkey under similar conditions. 



The dog's behavior demonstrates the necessity of eliminating 

 the possibility of the animal choosing or rejecting an alley on 

 the basis of the presence or absence of electrical charge. The 

 precaution taken in this work is adequate for that purpose. 



The present results raise further questions: what are the 

 optimal conditions as to brightness, surroundings, distance of 

 test-fields, range and relative intensities of wave-lengths and 

 adaptation for visual discrimination in these animals, as deter- 

 mined in similar tests ? 



