LITERATURE FOR 1913 ON THE BEHAVIOR OF 



VERTEBRATES 



STELLA B. VINCENT 



University of Chicago 



VISION 



Mammals. The work on vision, for 1913, although not so 

 extended as it has been in some previous years, is interesting. 

 The Watsons (57) report some experiments with rodents in 

 which they used the spectral light apparatus described in the 

 Yerkes- Watson monograph. They wished to discover whether 

 the differential response, in the use of color, was made on the 

 basis of wave length. Two animals were trained to react posi- 

 tively to red when red and green were presented simultaneously; 

 but, in later testing, it was found that, when the intensity was 

 varied or only one color was presented, the animals were neg- 

 lecting red and reacting to green alone. " One might increase 

 the green light enormously or eliminate the red altogether 

 without changing the accuracy of the responses. When, how- 

 ever, the intensity of the green approaches the threshhold — a 

 disturbance immediately manifests itself." Two white rats, 

 the one trained for yellow and the other for blue, and a black- 

 white rat and a gray Belgian hare, trained for blue, failed to 

 perfect a discrimination in over 500 trials when both stimuli 

 were present at full intensity. There was a rapid rise of the 

 habit, however, when only one, positive, stimulus was given. 

 The second stimulus was then introduced in gradually increas- 

 ing intensities. In the cases where the blue was the positive 

 stimulus the association was maintained up to nearly equal 

 intensities. The rat trained for yellow was disturbed by blue 

 when its energy was only one-eighteenth that of the yellow. 

 They conclude that the long wave lengths offer very slight, if 

 any, visual stimulation to rodents and that the response was 

 probably made to differences of intensity. 



The difficulties of such work and the dangers of premature 



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