J.— PSYCHOLOGY. 181 



persons seem generally clever with their muscles. While there seems 

 ample evidence for the existence of general intelligence, the results of 

 simple tests for isolated motor performances from which intelligence has 

 been excluded, as far as possible, give extremely low or negative correla- 

 tions with each other. Moreover, these results do not warrant belief in 

 any special connexion of simple motor abilities with intelligence.^^ 



From these results far-reaching deductions have been made by some 

 writers. One is that there is no general capacity, no ' motor type ' of 

 person. The conclusion concerning vocational tests has been drawn that 

 tests for ability in any performance give valid results only when the test- 

 performance is identical with that for which the test is being administered. 

 They support the ' sample ' as against the ' analogous ' test.''^ 



Yet an alternative explanation of Perrin's and Muscio's findings is 

 possible, based upon a suggestion made by Sir Henry Head to the present 

 writer. Their tests involve the simplest muscular co-ordinations. Many 

 of them were confined to limited parts of the body. From the tests used 

 by Muscio, demands upon intelligence were excluded. 



As a consequence, the bodily mechanisms involved may have been 

 controlled by relatively low levels of the nervous system. The significance 

 of the test-results, therefore, would not exclude the possibility that in 

 skilled performances a higher, more complex power might employ and 

 co-ordmate the simple mechanisms. 



Another consideration is important. In intelligence tests, that the 

 subjects will do their best is (perhaps not quite justifiably) taken for 

 granted. Yet it cannot be assumed that the motives urging university 

 graduates and undergraduates (the performers in these motor tests) to 

 excel in a simple, trivial and often boring motor test are identical with 

 those producing keenness in a recognised test of intelligence. For to do 

 very badly in several tests generally agreed to measure intelligence would 

 cause more shame in university people than proved inability to thread 

 needles or to loop wool quickly over pegs. 



The above tests, therefore, being concerned with simple motor abilities, 

 are important for the study of skill, rather as suggesting lines of inquiry 

 than as affording data. 



Transfer of training between motor abilities. 



Another method of attacking this problem is to re-set it in the well- 

 known form of the transfer of training.^'' Subjects are intensively trained 

 in some skilled activity xmtil their curves of practice have shown a marked 

 rise over a fairly long period. One discovers then if the undoubted ability 

 gained in the test-activity has been transferred to apparently related or 

 similar performances. "' Many ' controls ' are needed in such an experiment. 



^ F. A. C. Perrin, Jour, of Exp. Psych., 1921, 4, pp. 24-56 ; B. Muscio, British 

 Jour, of Psych., 1922, 13, pp. 157-84 ; see also Perrin and Klein, Psychology, London, 

 1927, pp. 356j5f. 



*^ This conclusion concerning simple motor dexterity has recently been supported 

 by the results of experiments. Cf. J. N. Langdon, Edna M. Yates and T. H. Pear, 

 ' The Nature of Manual Dexterity and its Relation to Vocational Testing,' Nature- 

 May 12, 1928, pp. 773-^. 



^' This technique has not been extensively used in the investigation of skill. 



