Color-naming, discrimination, cancellation, and coördination show up to much greater advantage. Even the preliminary trials in these tests show fairly high correlations with the final orders. The first two of these show little change as practice proceeds. In the case of the latter two tests, although the initial correlations are fairly high, there is nevertheless considerable increase as the trials proceed.
The meaning of these results seems to be that before one attempts to interpret individual differences as disclosed by performance in such a series of simple tests, he should have clearly in mind the distinction between temporary proficiency and ultimate capacity. If he is interested, for example, in determining the vocational prospects of a youth, or the relative merits of candidates or culprits, it is important that he realize that relative abilities in many of these laboratory tests may be changed quite beyond recognition by continued work. It is highly desirable to know more than we now know concerning the degree to which initial and intermediate trials in these tests reflect final capacity. In the past the question seems hardly to have been asked. Individual differences in early trials, in some tests, are fairly significant of the working level to which the performer may be brought later. In other tests this is not the case. On the significance of these early trials may depend, in many cases, the vocational value of the particular test.
Changes in the nature of the tests, variations of methods of attack, and specific improvement in the directness, independence and rapidity of the special nervous connections concerned--these three factors would all declare themselves in the form of "changes in ability." A useful piece of work in the case of all tests will be the analysis of the nature of the changes resulting from practice. But in any case the presence of these changes in correlation shows that we are not, in early trials, measuring the same tendency or capacity in all performers. The concrete tasks of daily life doubtless show just such qualitative changes, during practice, as we may suppose to be present in some of these tests. Just as it is ultimate capacity in daily life that is, with a given set of incentives, most important, so in the laboratory the measurement of "ability after practice" ought to be more emphasized than it is at present.