270 REPORTS ON THE STATE OF SCIENCE, ETC. 



Vocational Tests. — Re/port of Committee (Dr. C. S. Myers, Chairman ; 

 Dr. G. H. Miles, Secretary ; Prof. C. Burt, Mr. F. M. Earle, Dr. 

 L. C. Wynn Jones, Prof. T. H. Pear, Prof. C. Spearman). 



A. Introduction. 



In the Report of last year it was suggested that the general absence of correlation 

 between ' motor ' tests might be partly due to ( 1 ) the low reliability of the tests 

 employed, (2) the disturbing effects of ' practice ' and ' fatigue,' and (3) the disturbing 

 influence of other ' abilities ' which the tests employed to measure ' motor ' functions 

 are not devised to measure, but which nevertheless may affect the scores. It was 

 further suggested that this absence of correlation might also be accounted for by the 

 specific nature of the movements commonly involved in the tests, and that when 

 such relatively simple and specific movements were combined into the more complex 

 operations employed in assembling work these operations might exhibit a much 

 closer relationship than do their simpler components. 



In the present report it is impossible to do more than describe, briefly, the general 

 lines along which work has been carried out in the light of these suggestions and to 

 indicate the main conclusions. 



B. The Main Problems. 



The following are the main problems with regard to which the experiments have 

 been planned. 



1. The problem of Accuracy. How far does each of the tests employed in the 

 research afford a reliable measure of ' ability ' ? 



2. The nature of the Abilities involved. How are the abilities measured by the 

 various assembling tests related to one another and to other abilities, in particular 

 to ' general intelligence ' and to ' mechanical aptitude ' ? 



3. The effect of Practice, Improvability. (i) How far can we predict from the 

 scores made initially at the various assembling tests the ability which an individual 

 may attain after practice ? (ii) What is the character of the practice curve ? (iii) How 

 far does practice at one operation influence ability at another ? 



4. The nature of the mental 2''>'ocesses involved iti Assembling, (i) What are the 

 processes operative at first ? (ii) How do these change as practice continues ? 



C. General Plan. 



The assembly operations were divided into two classes, viz. (i) operations in which 

 the subject is first required to think out hoiv to put together the parts of the object 

 he is called upon to assemble, and (ii) operations in which the mode of assembling is 

 already known and where therefore the subject has only to perform the actual 

 assembling. These have been termed, provisionally, ' intelligent assembling,' and 

 ' routine assembling,' respectively. 



The principal tests employed have been tests of these two types of assembling, 

 together with tests of ' general intelligence ' and tests of ' mechanical aptitude.' 

 Spearman's ' tetrad- difference ' criterion has been employed to determine the presence 

 of factors involved in these different groups of tests. 



The tests have been chosen so as to include a variety of movements, both in type 

 and in complexity ; and the subjects include an ' adult ' group of men and women, 

 an elementary school-boy group, and an elementary school-girl group. An 

 investigation of ' age ' and ' sex ' differences is thus made possible. A ' backward ' 

 class of school girls has also been tested (for details see later). 



To investigate the influence of early practice on ' reliability,' each of the routine 

 tests was repeated several times (usually five — each ' test ' itself consisting of, usually, 

 ten repetitions of the operation to be tested), and the intercorrelations of these trials 

 were calculated. 



To investigate the effects of more prolonged practice, the subjects were then 

 divided into (a) two (or, in the case of the adult subjects, four) practising groups, 

 who practised certain of the routine operations daily, and (2) a control group who 

 ' rested ' while this practice was in progress. On the termination of practice both 

 ' practisers ' and ' controls ' were re-tested on all routine tests. The practice period 



