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SCIENCE 



[N. S. Vol. XXXrV. No.! 



elementary sensations and feelings is well an- 

 alyzed. He considers sensation and afltection 

 distinct classes, since the former possesses " a 

 sort of local mark " -which " affection lacks " 

 (p. 147). In discussing the properties at- 

 tributed by various authors to sensations and 

 affections the writer is remarkably free from 

 bias (pp. 104, 151). He advocates the word 

 " mode " to indicate the fundamental sorts of 

 sensation. Such distinctions as noise and 

 tone are different modes within the same 

 sense. Several tables are given of the sensea 

 and their modes (pp. 95-100), and here as 

 elsewhere the tables are excellently presented. 

 The synthetic discussion is good so far as it 

 goes; but unfortunately it stops with percep- 

 tion and imagination. There is no adequate 

 treatment of thought. 



In Part IV. Professor Yerkes brings to- 

 gether a remarkable number of psychological 

 generalizations and laws. This portion of the 

 book deserves special study, in view of the 

 claim in various quarters that psychology is 

 not an exact science. The author is at his 

 best here. He notes fifteen laws of sensi- 

 bility (threshold, contrast, local sign, etc.), 

 three laws of perception, and several laws re- 

 lating to the affective life, attention and asso- 

 ciation. The collection and formulation of 

 these la^ws is a valuable contribution to the 

 science. 



Part V. extends these laws to wider gen- 

 eralizations or " explanations " of mental phe- 

 nomena. The author adopts the parallelistic 

 view, which demands that psychology study 

 psychical events by themselves, before attempt- 

 ing to correlate them with physical happen- 

 ings. " The essence of the causal relation is 

 uniformity of the order of events" (p. 328). 

 It is found that sensation always precedes 

 the after-image, disagreeable affections are 

 "called up" by sensations, etc. (p. 334). On 

 the very basis, therefore, on which we accept 

 physical causation, these must stand as in- 

 stances of psychical causation, and we can 

 affirm that " certain mental conditions bring 

 about the formation of an idea, an emotion, 

 a judgment" (p. 336). 



Parts II., IV. and V. belong together, and 

 the interpolation of the genetic discussion 

 (Part III.) is a break in continuity. However 

 much the reader may sympathize with the 

 author's desire to introduce genetic notions 

 as early as possible, he will feel that the pre- 

 sentation of this topic should follow Part V. 

 The phylogenetic account, although brief, is 

 clear and thorough, as one would expect from 

 a writer of Professor Yerkes's training and 

 sympathies. Nevertheless, one misses the help 

 which a discussion of behavior at this point 

 would have aft"orded. This is left till Part V., 

 where the relations of behavior and conscious- 

 ness are considered in detail. The ontogen- 

 etic chapter is somewhat meager. The main 

 stages of mental development from infancy to 

 maturity are examined, but there is no at- 

 tempt to trace the actual course of individual 

 development. Part VI., on the control of 

 mental life, supplements this chapter. The 

 author points out the relation of psychology 

 to education and eugenics, illustrating the 

 effects of good and bad heredity by the stri- 

 king contrast between Jonathan Edwards's 

 descendants and the notorious Jukes family. 

 Failure to examine the thought processes is 

 the only important omission. The cursory 

 treatment of volition and other aspects of the 

 motor life is in logical keeping with the au- 

 thor's purpose to subordinate behavior to con- 

 sciousness. A novel distinction suggested 

 between lightness and brightness (p. 122) is 

 the only departure from accepted positions 

 which introspection is likely to challenge. 

 The volume shows careful preparation and 

 abounds in good illustrative examples. Excel- 

 lent judgment is used in the selection of 

 material, and opposing standpoints are pre- 

 sented with remarkable fairness. There are 

 innumerable citations and quotations, espe- 

 cially from recent writers. At the end of 

 each chapter is a class exercise, usually related 

 to the subject matter, which serves as an in- 

 troduction to experimental methods. Th» 

 clear style and skillful avoidance of technical 

 expressions make the volume especially suit- 

 able for beginners. 



