The evidence now at hand suggests that the incomplete correlation comes, in part at least, from the fact that some of the tests of momentary achievement do not fully represent the ultimate capacities of the individuals measured. At this point the line is relatively slow in advancing. The obstacles encountered consist partly in our incomplete information concerning which of the tests at once reveal final capacity and which do not. This information must necessarily come slowly because of the difficulties involved in securing the cooperation of subjects who will submit to the prolonged series of measurements which such investigations involve. Such data as are available, while inadequate to constitute proof, suggest very strongly that those tests which are now in most common use correlate closely with each other when the limit of practice is reached in all of them. If subsequent work confirms this suggestion, the determination of the factor of general intelligence may proceed on either of two bases. Either we may use a very few trials of tests in which such trials may be found to indicate ultimate capacity, or we may use a small number of tests, but continue the measures until the limits of practice are reached. But there is probably another factor in part responsible for the incompleteness of the correlations between test records and direct measures of vocational success. This is the fact that characteristics other than general intelligence play a conspicuous part in daily life. The interests, the incentives, the emotions, and the equipment of instinct and habit, which show themselves in such traits as curiosity, competition, honesty, loyalty, promptness, patience, the play impulse, etc., do not count for nothing in vocational activity. Moreover, it is quite likely that, in addition to the common fund of intelligence, each individual possesses in his or her own degree, certain more specialized capacities and aptitudes, for the complete measurement of which the available tests are inadequate. The graded "product scales," however, represent a definite step toward the measurement of many of these specific capacities.