BEHAVIOR OF VERTEBRATES 459 



as (a) the direct method, (b) the simple reflection method, 

 (c) the double reflection method of Watson and (d) the double 

 reflection method of Kellogg. The authors discuss the advan- 

 tages and disadvantages of each scheme and their paper is 

 followed in the same journal by one by Watson (39) in which 

 he describes his own recording device in greater detail. His 

 circular maze is a maze so planned as to make it very easy to 

 increase the complexity by adding new units, etc., and with 

 this maze goes his excellent recording device. 



A sympathetic description of the Pawlow method with animals 

 is found in Morgulis' paper (24). The article is devoted 

 chiefly to the neuro-psychical phases but the method with its 

 implications is of interest to all who work with vertebrate 

 animals. 



Similarly the article by Carr (3a) on the Principles of Selec- 

 tion in Animal Learning will attract all who attempt to analyze 

 animal behavior or to explain their mode of learning. It is 

 impossible to summarize an article which is itself so compact. 

 The author says, " Selection and elimination are the diverse 

 effects of a single process or mechanism. All connections tend 

 to be preserved; all develop in strength and functional efficiency 

 during the learning process, but their development proceeds 

 unequally. The unsuccessful tendencies are not eliminated in 

 the sense of being torn out by the roots; they are eliminated 

 only in the sense of not being aroused in that situation. The 

 strongest and most prepotent tendencies of the group function 

 first and dominate the situation. The successful act is selected 

 because it finally becomes the most prepotent in the group; all 

 others are eliminated, or better are 'suppressed' because of 

 their lesser development in functional efficiency. 



1 ' The problem of determining the various principles of selection 

 thus resolves itself into a search for those factors which favor 

 the retentive development of the successful act at the expense 

 of the many failures. These principles are relative recency, 

 relative frequency, and relative intensity." 



These principles are then applied in a careful analysis to 

 three types of animal problems. The paper concludes with a 

 brief comparison of these selective principles with that of 

 pleasure-pain which has been advocated so frequently by others. 



