The Sense of Sight: Brightness Vision 99 



as a motive in animal behavior experiments objections 

 which in my opinion render it almost worthless in the case 

 of many mammals. These are the discomfort of the animal 

 and the impossibility of keeping the motive even fairly con- 

 stant. However prevalent the experience of starvation may 

 be in the life of an animal, it is not pleasant to think of sub- 

 jecting it to extreme hunger in the laboratory for the sake of 

 finding out what it can do to obtain food. Satisfactory re- 

 sults can be obtained in an experiment whose success depends 

 chiefly upon hunger only when the animal is so hungry that 

 it constantly does its best to obtain food, and when the 

 desire for food is equally strong and equally effective as a 

 spur to action in the repetitions of the experiment day after 

 day. It is easy enough to get almost any mammal into a 

 condition of utter hunger, but it is practically impossible to 

 have the desire for food of the same strength day after day. 

 In short, the desire for food is unsatisfactory as a motive in 

 animal behavior work, first, because a condition of utter 

 hunger, as has been demonstrated with certain mammals, 

 is unfavorable for the performance of complex acts, second, 

 because it is impossible to control the strength of the motive, 

 and finally, because it is an inhumane method of experi- 

 mentation. 



In general, the method of punishment is more satisfactory 

 than the method of reward, because it can be controlled to a 

 greater extent. The experimenter cannot force his subject 

 to desire food; he can, however, force it to discriminate 

 between conditions to the best of its knowledge and ability 

 by giving it a disagreeable stimulus every time it makes a 

 mistake. In other words, the conditions, .upon which the 

 avoidance of a disagreeable factor in the environment de- 

 pends are far simpler and much More^-coristanr/'than: those 

 upon which the seeking of an agreeable .factor depends. 



