ON VOCATIONAL TESTS. ovr 
activity. The type of test chosen was that used for assembly work in the hope that 
_ in the course of this analysis facts that would be useful for the work of vocational 
guidance would emerge, and further that the debatable relation between general 
_ intelligence, mechanical aptitude and manual dexterity might be cleared up. There 
_ appeared to be also the possibility of obtaining more information which might improve 
the present restricted view on motor ability. 
The report for that year describes the tests carried out and the data obtained. 
_ The method of work followed was to select a rather complicated assembly operation 
__ and to find out how proficiency at certain specifically chosen tests was related to special 
ability at the operation. The result indicated that routine assembly operations have 
more in common than laboratory motor tests have in the past suggested. It was 
also evident that the lack of correlation usually found in motor tests may be due to 
the lack of reliability in the tests themselves. This indicated a need for closer 
analysis and more systematic classification of motor tests. The experimental work 
done suggested that practice and fatigue might have an effect on such motor tests. 
It also appeared that the ‘ abilities ’ unduly influenced the score made at these ‘ motor ’ 
tests of routine assembling operations. 
This preliminary work seemed encouraging and during the year 1929-1930 the 
work was extended to a larger number of subjects. The assembly work was carefully 
graded in complexity and to those who were doing the assembly tests, additional tests 
of general ability and mechanical aptitude were applied. In all, 47 adults, 70 boys, 
59 normal girls, and 22 retarded girls were tested and examined. The effects of 
practice were also studied. One important point to determine was the degree of 
reliability of these tests ; and the conclusion arrived at was that a single trial of an 
assembly test was highly unsatisfactory as a measure of ability. It was found, 
further, that in a number of trials the sum of the best, next best, etc., trials are 
almost as reliable as the total of all scores. It was found that the influence of random 
errors on reliability was far greater than that exerted by practice or fatigue during 
the trial. It was found that reliability depended on the number of repetitions of the 
_ Operation constituting the measure rather than on the length of time required for 
the operation itself. Further practice had no marked influence on reliability. 
The results reported in 1930 were the outcome of a partial analysis of the data 
obtained. A more thorough-going statistical analysis was necessary, and during 1930- 
1931 this has been done with usefulresults. Statisticalanalysis hasshown very definitely 
that there exists (a) a general factor, (b) a mechanical factor associated with mechanical 
insight and invention, and (c) a motor factor associated with the manipulative side 
of assembly work. Interesting facts concerning the growth of practice have been 
obtained. The practice curve for adults has been examined. In all operations there 
are wide individual differences which tend to dominate as practice continues. The 
course of progress in practice appears to be the same for most individuals, namely, a 
steep initial phase which seems associated with the cognitive processes involved in 
learning how to manipulate material, followed by a much less steep secondary phase 
which is associated with ‘motor’ learning—that is with acquiring speed in the 
manipulative processes after the method of manipulation has become clear. The two 
phases are more distinct in the more complex assembling operations and tend to 
disappear in the simpler operations. There are well-marked differences in the 
‘smoothness or daily variability shown in the curve. These are especially noticeable 
_ in the more complex operations. Similar features appear in the curves of practice 
_ of schoolboys: generally the curves are moreirregular, indicating less rapid and less 
_ continuous improvement than is shown in the adult curves. J 
The results as a whole suggest that where speed is the chief factor, the boys are 
_ of superior ability initially and show the greater improvability ; whereas where 
‘success depends on the accurate adjustment of one part to another, the adults are 
‘Superior in both respects. Where the operations call for a large measure of both speed 
and accuracy, the boys may do better at first but the adults show the greater 
improvability. Furthermore, although considerable improvement is shown by most 
“subjects during the practice period, there is a fairly close correspondence between the 
_ tank orders on the first day and those on the last. 
___ The question of transfer has also been examined, both with ‘adult’ groups and 
with elementary schoolboys. The number of subjects in the practised group has 
been increased during the year. The adults now number 33, with 17 ‘ controls’ ; 
the schoolboys number 38, with 32 ‘controls. The practisers were divided into 
‘ere oa ~ 
