August 15, 1913] 



SCIENCE 



221 



multitude of disconnected papers. As an 

 outcome of suggestions made at the Dun- 

 dee meeting the section will meet with the 

 anthropologists to discuss the educational 

 value of museums. A discussion on the 

 function of the modern university in the 

 state promises to be very attractive, as the 

 heads of the newer universities, including 

 Sir Oliver Lodge, have promised to take 

 part. The president of Stanford Univer- 

 sity, Mr. Alfred Mosely and Miss Burstall, 

 of the Manchester High School for Girls, 

 are also expected to contribute to the dis- 

 cussion. The discussion arranged with the 

 psychological subsection of Section I will 

 be concerned with the general question of 

 the need for research in education, and with 

 the specific researches which have been 

 made into the vexed subject of the psy- 

 chology of spelling. Two other discussions 

 will be concerned with manual work in edu- 

 cation and the registration of schools. The 

 importance of the latter question was 

 brought out by a committee at the Dundee 

 meeting, while the importance attached to 

 manual training is shown by the new em- 

 phasis which is now being laid on it in 

 educational practise. 



Professor T. B. Wood will preside over 

 Section M (Agriculture). In his address 

 he proposes to review the results of twenty 

 years' work in agricultural science, to 

 point out the successes and failures, to 

 discuss the reasons for success or failure, 

 and to endeavor therefrom to make sugges- 

 tions for the future. As already stated, 

 the section will engage in joint discussions 

 with the botanists (on barley culture) and 

 the physiologists (on the physiology of re- 

 production). Communications will also be 

 made to the section by Sir Richard Paget, 

 on the possibilities of partnership between 

 landlord and tenant; Professor Fraser 

 Story, on German forestry methods ; Dr. H. 

 B. Hutchinson and Mr. K. McLellan, on 



the partial sterilization of soil by means of 

 caustic lime; and Dr. Winifred B. Brench- 

 ley, on the weeds of arable land. 



TSE PRINCIPLE OF MENTAL TESTS 



The standpoint of applied psychology is 

 implicit in the conception of mental tests. 

 Tliey represent a group of procedures, usually 

 of simple teclmique, developed so that our 

 knowledge of individual differences may, as 

 Cattell puts it, be employed to guide human 

 conduct. To justify themselves, they must 

 earn their bread in terms of usefulness for the 

 questions of life. In this respect they differ 

 from the leisure-class problems of true psycho- 

 logical science, which are exalted above these 

 vulgar necessities. 



Two broad functions of psychological tests 

 are distinguished. One is the measurement of 

 changes in individuals under controlled differ- 

 ences in experimental conditions. The studies 

 of Hollingworth on caffeine and of Winch on 

 the effects of school work are among the recent 

 examples of this type. Here the problem has 

 usually been defined in the determination of 

 central tendencies. To this limit, measure- 

 ments can be made with comparative relia- 

 bility, because the external conditions are well 

 controllable, and the errors due to subjective 

 factors tend, on the whole, to compensate. 

 That is, a gain of 10 per cent, in the same 

 individual for a second performance repre- 

 sents a gain of 10 per cent, in the same 

 abilities as were concerned in the first per- 

 formance. The more difficult question of just 

 what these abilities represent in the individual 

 ease has been a secondary one for these studies, 

 not usually coming into prominence. 



It must be squarely faced, however, in the 

 other function of psychological tests, that of 

 measuring and interpreting the differences 

 between individuals under similar immediate 

 conditions. One may not say because Peter is 

 10 per cent, better in a memory test than Paul, 

 that it is due to a 10 per cent, superiority in 

 the same abilities as Paul's. It is not a diffi- 

 cult matter to construct tests in which con- 

 sistent and certain individual differences ap- 



