INTRODUCTION 9 



the analysis of instinct into simpler processes, and the 

 different views of the origin and evolution of instinct. 

 Considerable space is devoted to the transition between in- 

 stinct and intelligence, and the evolution along the lines 

 of plasticity and ready modifiability of behavior which has 

 prepared the way for the appearance of intelligence. This 

 is followed by a general and confessedly incomplete sketch 

 of the gradual evolution of intelligence in the animal king- 

 dom, and a discussion of some of the evidences for the ex- 

 istence hi the higher animals of a certain power of making 

 inferences which some modern psychologists have claimed 

 is not founcf in any sentient creature below man. 



A comparative survey of the actions of animals shows us 

 that behavior is very much the same sort of thing wherever 

 found. It is one of the many valuable contributions of the 

 great pioneer in genetic psychology, Herbert Spencer, to 

 have shown the fundamental unity of biological and psycho- 

 logical processes in all their varied manifestations. Instinct, 

 memory, volition and reason are all parts of that general 

 process of adjustment of the organism to its environment, 

 in which life in all its stages essentially consists. As we 

 pass from lower to higher forms we have an increase in the 

 complexity and perfection of the adjustments; the corre- 

 spondence increases in space and in time, in definiteness and 

 in generality, but everywhere it is "the adjustment of 

 internal relations to external relations." This conception 

 of mental life marks an important advance upon the psy- 

 chology current in Spencer's early years; it set aside the 

 arbitrary distinctions of the so-called "faculties" and pre- 

 pared the way for a clearer insight into the gradual unfold- 

 ing of mind which the labors of genetic psychologists are 

 slowly giving us. 



