May 19, 1899.1 



SCIENCE. 



713 



records of feelings with the actual mental 

 ability displayed shows that the former are 

 not a parallel or measure of the latter. 



The quantitative results obtained would 

 seem to show that the degree of real inabil- 

 ity caused by mental work was very much 

 less than has been supposed ; that in ordi- 

 nary life nature wai-us us by the complex 

 feelings mentioned not to work mentally 

 some time before we are really incapacitated 

 for work. They would also suggest that 

 the results which those investigators who 

 have sought to measure mental fatigue 

 in school children have obtained were due 

 to the use of methods which did not meas- 

 ure the inability, but the distaste for mental 

 work, of the children. One is tempted to 

 put forth the paradox that real mental in- 

 competency is the rarest of all reasons for 

 stopping or decreasing mental effort. 



The methods used to estimate the ability 

 to do mental work are to some extent new 

 and so worth mention. The chief was the 

 mental multiplication of three figures by 

 three (e. g., 794x683); of two figures by 

 three, and in some cases four by four. This 

 work, at least for the subjects of these ex- 

 periments, required the utmost concentra- 

 tion. It is very fatiguing (in the ordinary 

 sense of the word). Any interruption or 

 distracting influence is felt at once and 

 makes successful work impossible. So one 

 would suppose that it ought to show the 

 influence of decreasing power to do mental 

 work as cleai-ly as could anything. The 

 amount of work and the mistakes can be 

 easily and accurately recorded. 



Another method involved the addition of 

 columns of twenty numbers, each of five 

 figures. This does not require close con- 

 centration, but the work done should show 

 perfectly the fact of mental fatigue in so far 

 as that involves the accuracy and speed of 

 associations between ideas. The speed and 

 accuracy of discrimination of the lengths of 

 lines and of the perception of letters were 



also used. The tests were arranged so as 

 to eliminate the eifects of practice. 



Edward Thorndike. 

 "Westeen Reserve University. 



SCIENTIFIC BOOKS. ' 



The Development of English Thought: A Study in 

 the Economic Interpretation of History. By 

 Simon N. Patten, Ph.D., Professor of Polit- 

 ical Economy, Wharton School of Finance 

 and Ecouomy, University of Pennsylvania. 

 New York, The Macmillan Co. 1899. Pp. 

 sxvii + 415. 



"We don't know him; let's heave half a 

 brick at him." The process is simple, obvious 

 and, to the heavers, effective. There are only 

 too many grounds for the fear that Professor 

 Patten's new work will be treated as a vile 

 body for this old experiment. Everyone knows 

 how easy it is to discredit generalization by 

 advancing negative instances ; how sweet to 

 cavil at principles by alleging that facts have 

 been twisted to fit ; how seductive to empha- 

 size the specialist's standpoint and to magnify 

 its abounding limitations. I do not exaggerate 

 in saying that it is long since I have encoun- 

 tered a book which lies so open, so invitingly 

 open, to these insidious attacks ; or, on the 

 contrary, one which proves so conclusively the 

 unfairness, superficiality, even stupidity, of 

 , such criticism. For Professor Patten sets 

 theory in the forefront of his discussion, and the 

 body of his work sees the persistent application 

 of this theory. Nevertheless, he who runs may 

 read that, in the author's mind, the theory 

 came last, being the inference from his detailed 

 investigations, the final form in which the mul- 

 titudinous facts shaped themselves — ceased to 

 be mere isolated phenomena and became ration- 

 ally one. 



Professor Patten's theory reposes on a quasi- 

 psychological basis. Sensory ideas, or ideas 

 brought by the senses from the environment, 

 constitute the material of knowledge ; and 

 " sensory knowledge is merely the amplification 

 and classification of the differences perceived by 

 the senses. ' ' (2) Such processes produce series 

 of mental images ; these, in turn, occasion rela- 

 tive motor reactions. Consequently a "man's 



