448 JOHN B. WATSON AND K. S. LASHLEY 



or both of the following conclusions: that (i) a difference exists 

 between the chromatic luminosity values for the chick and 

 those for the human being ; or (2) the chick exhibits a qualitatively 

 determined preference such as is apparent in some other animals. 

 From results which the reviewer has in his hands, it is perfectly 

 clear that Breed's first contention is contiary to fact, the chick's 

 luminosity curve for monochromatic light being almost entiiely 

 similar to that of the human being. Whether we are foiced to 

 accept the second part of his conclusion depends upon the 

 extent to which Breed and others have bi ought out all the 

 remaining facts in the case. 



The author finds further that chicks are able to select one 

 of two colors at the brightness indifference point. 



One of the animals gave convincing evidence of ability to 

 make the circle-square distinction, while another animal quickly 

 acquired the small-large habit — two circles eight cm. and five 

 cm. in diameter respectively were used. 



Mammals. Vincent (26) has given a very valuable table 

 showing anatomical features of the mammalian retina. It is 

 compiled from various researches dealing with the presence or 

 absence of rods and cones, their relative number, distribution, 

 the nature of the fovea and sensitive area, refraction, stereo- 

 scopic vision, etc. 



Hoge and Stocking (12) in their study of motives have shown 

 that the albino lat and hooded black and white rats can form 

 a habit of responding positively to one of two white lights (when 

 the intensity of one was two c. p., and the other sixteen c. p.). 

 The number of trials required for the formation of this habit 

 varied with the motive used, one animal requiring 490 trials, 

 two others completing at the end of about 550. The authors 

 show that in the discrimination of these lights, the offering of 

 food with success and punishment (electric shock) with failure 

 is more advantageous than the giving of either food alone or 

 punishment alone. 



Lashley (15) made a long series of tests upon albino rats to 

 test their sensitivity to difference in form and size. In the 

 first place he found that the introduction of a slowly moving 

 sector in the pathway of one of the light stimuli produced no 

 hastening of the habit of discrimination. He was enabled to 

 get one animal to discriminate between vertical and horizontal 



