14 JOHN B. WATSON AND MARY I. WATSON 



CONCLUSIONS 



i. The evidence seems to justify the conclusion that the long 

 wave lengths stimulate the visual receptors of the rodents very 

 slightly or not at all. Where their spectrum begins at the red 

 end cannot be decided by the above type of experimentation. 



2. Experiment II offers good but not absolutely conclusive 

 evidence that the rats can respond only to difference in intensity 

 of monochromatic light. On account of the low stimulating 

 value of red and yellow our choice of stimuli was not very good. 

 Blue and green would have been better. To the adherents of 

 color theories the denial of a response based upon wave length, 

 both in the case of red and green and of yellow and blue is the 

 equivalent of denying the possibility of a response on the basis 

 of wave length anywhere in the animal's spectrum. If the data 

 on blue and green were at hand and spoke as clearly for intensity 

 difference, ' we believe that we could say with some certainty 

 that wave length is not a factor in the visual responses of rodents. 



