One of the least important of these factors is the variability of individual performance. In the beginning of the experiment each individual is more variable than at later points in the curve. This momentary variability need not be supposed to affect all the tests in the same way nor all individuals in the same direction. This fact may then tend somewhat to reduce the correlation of the preliminary trials and may in some cases materially affect the first five or ten trials. Beyond the twenty-fifth trial the variability in these tests is much reduced, and particularly so in the measures here used, which are in all cases, after the preliminary trial, the medians of five successive trials.
Another factor that deserves mention is the possibility of change in the character of the tests themselves, through practice with them. It is quite probable, for example, that the opposites test comes, after many repet.i.tions, to resemble more and more that type of process or function involved in color-naming. The responses become more and more intimately a.s.sociated with the stimulus words, the suggested responses to each word become more and more limited in number and in most cases reduced to a single word for each stimulus. This state of affairs is true of color-naming at the very beginning of the experiment. As the order of the stimulus words is changed at each trial, the test may come to involve more and more the simple task of giving merely the quickest possible a.s.sociation of the right response, and the overcoming of inhibitions and interferences of a more or less general sort, with less and less emphasis on the element of selection. Much the same may also be true of the addition test. It is in these three tests that the increase in correlation is most marked, and the actual coefficients highest at the end of the experiment. Careful a.n.a.lysis of what takes place as one improves in these simple tests would no doubt yield interesting material.
But these two factors--decrease in variability and change in the character of the tests--seem to be far from sufficient to account for the results.
The tapping test remains much the same type of process throughout, the only apparent modifications consisting of slight changes in method and perhaps some gradual changes in the muscles. There is certainly no reason for suspecting that tapping and opposites or tapping and discrimination become, as tests, more alike because of frequent repet.i.tion. But the increase in correlation is clear in both these cases. Again, it is well established that the discrimination reaction, in the form here used, also tends to become reflex through practice, the conscious discrimination coming only after the correct reaction is made. These experiments called for between 3,075 and 4,100 single discrimination reactions on the part of each observer, which would afford ample time for such a change to show itself.
Mere change in the character of the test would then lead us to expect color-naming, opposites, and adding to come more and more to resemble discrimination reaction. But they do not, if the coefficients may be taken as evidence. The coefficients of these tests with discrimination show no tendency to increase, even by the end of the experiment. The a.s.sumption of increasing similarity in the character of these pairs of tests would seem gratuitous. Moreover, if there were such increase in similarity, and this be also supposed to account for the higher correlation of color-naming and opposites with adding, coordination and adding should show the same increase in correlation. Just the reverse is actually the case, the correlation of coordination and adding decreasing consistently.
Some further factor must then be responsible for the general increase in correlation, aside from decrease in variability (which affects only the first few trials) and progressive qualitative approximation of the tests (which is seen to be inadequate). The doctrine of "general ability" or "general intelligence" at once suggests itself in this connection. If there is such a thing as "general ability" or "general intelligence," we should expect all samplings of that ability to correlate more and more as the measures came to be truer samples. We might indeed expect to find evidences of this general ability only when measuring the "ultimate capacity" of the individuals concerned. The momentary ability revealed in initial trials, or even in the first half-dozen trials, in a given set of tests might well be expected to show only low degrees of correlation. These trials would not be measures of ultimate capacity, but would be largely determined by previous practice, chance variability, momentary att.i.tude and initial method of attack. They would, in short, be samplings only of momentary ability, not of final capacity.
Or if the a.s.sumption of a common factor be rejected, the present evidence tends strongly to support our earlier conclusion concerning the positive correlation between desirable mental functions. Some form of the doctrine of "general ability," at any rate, seems to be supported. But the conclusion seems to call for the qualification that "general ability" shall have reference to _final capacity_ rather than to _momentary performance_, if the correlations are to be high. If each individual be given the opportunity to attain his limit of efficiency, his highest level of performance, then, when these final limits are reached, individuals who excel their fellows in one type of work will also tend to excel in other types of work.
The theory and practice of tests has in the past been too content to rest its claims on the meager results of a few preliminary samplings of an individual"s ability. The fact that, even when a great variety of such samplings of a given individual are aggregated and balanced off against one another, few results of real diagnostic value are achieved should be sufficient warning against this tendency. My conviction is that for this purpose we shall find it necessary to determine the individual"s "limit of practice" in the various tests before we shall secure diagnostic results which will be verified by the individual"s subsequent achievement in daily life. We should know much more than we now know concerning the tendency and meaning of such correlations as show close relation between initial performance and ultimate capacity. This is particularly true if we wish to extend the method of tests beyond educational diagnosis and to use them as a means of vocational guidance or of industrial selection. For educational diagnosis we wish primarily to know what kind of practice the individual most needs. For vocational and industrial purposes we need rather to know what limits the individual can eventually reach, in given kinds of performance, as the result of practice, and to what degree his present equipment of incentive renders probable the actual achievement of this limit.
On the question of the significance of preliminary trials and the effects of practice on the relative standing of individuals in their group, there are important facts to be considered. In the direct application of mental tests it has too often been a.s.sumed that the actual performance of an individual, in one or a dozen trials at a given task, is in some way or other significant of that individual"s final capacity in such work. It is true that several investigators have studied the effects of practice on individual differences. These workers were interested above all in questions as to relative rate of improvement, or amount or permanence of gain. Such studies have produced suggestive results, although they have been based, for the most part, on records of only a few subjects or on relatively few practice trials.
To what degree are individual differences after a given number of trials indicative of the final maximum capacity of the individuals concerned? At what various rates do the determining factors enter into the practice curves of a group of workers? What manner and amount of displacement in their relative order of ability are thus produced? At what point or points in the curves do the individuals a.s.sume their final order of relative capacity after training? How do the replies to these questions vary with the character of the task?
In the case of the experiments already described, record has been here taken of the following points in the curves of practice:
Preliminary trial called initial trial Median of trials 1 to 5 called 5th trial Median of trials 20 to 25 called 25th trial Median of trials 46 to 50 called 50th trial Median of trials 76 to 80 called 80th trial Median of trials 126 to 130 called 130th trial Median of trials 171 to 175 called 175th trial
At each of these points the thirteen subjects were arranged in order of relative ability for the test at the given stage of practice. Each of these orders, or cross sections, of the group of practice curves was then correlated with the final order of position as shown in trials one hundred and seventy to one hundred and seventy-five. Table 24 gives the coefficients of correlation derived in this way. A careful study of this table will prove instructive.
TABLE 24
SHOWING THE CORRELATION OF ULTIMATE CAPACITY WITH CAPACITY AT DIFFERENT POINTS IN THE CURVE OF LEARNING
(See Text for Explanation)
-----------------------------------------------------------Final The TestPrelim-5th25th50th80th130thTrialinaryTrialTrialTrialTrialTrial175th --------------+-------+-----+-----+-----+-----+------+----- Adding.15.19.87.87.97.961.00 Opposites-.08.62.49.83.94.981.00 Color Naming.68.89.86.91.97.971.00 Discrimination.68.62.60.50.50.791.00 Cancellation.67.68.88.69.93(1.00)-- Coordination.52.79.77.90.95(1.00)-- Tapping.23.48.63.68.69.891.00-------+-----+-----+-----+-----+------+----- Averages.41.61.73.77.85.921.00 -----------------------------------------------------------
It is at once evident that the preliminary trial is by no means always a measure of the final relative capacities of the individuals tested. The average of all seven coefficients increases from .41 at the preliminary trial to .92 at the one hundred and thirtieth trial. As the trials proceed then, the relative positions of the thirteen individuals become more and more definitely fixed, but in the beginning the indication is obscure. The rate of this process, however, varies with the test, and to a considerable degree. Adding shows changes in position which effect a correlation of .87 only after the twenty-fifth trial. Beyond this point there is little change, the eightieth and one hundred and thirtieth trials correlating equally well, and practically perfectly, with the final order. After twenty-five trials, then, the final capacities of the individuals in the adding test may be said to be indicated fairly accurately. Opposites, in the fiftieth trial, yields a coefficient equal to that of addition in the twenty-fifth trial, and by the eightieth trial the correlation may be said to be complete. Only after fifty trials, then, can the test be said to yield comparative measures which reflect the individual"s final capacity in this form of controlled a.s.sociation. In the case of tapping it is only at the one hundred and thirtieth trial that the correlation with final position exceeds .69.
These results may be easily comprehended by thinking of each test (as for instance the tapping test) as a prolonged race, consisting of a large number of heats (205 separate trials). All individuals begin with a running start, their respective initial speeds depending on the momentum they have acquired through a certain amount of previous practice, and on such momentary ability and zeal as they possess at the time. But as the succeeding "heats" or trials occur some individuals who were originally in the lead begin to lose ground in relation to others who, though initially slower, are now speeding up and overtaking the leaders. Still others may retain their original relative positions to the end of the race. In the table of coefficients, a correlation of 1.00 indicates that at that point the ultimate relative positions of the contestants have at last become established. The nearer the figure approaches zero the more uncertain are the relative positions at the particular trial. To terminate the race at a point where the correlation is low and to reward the contestants according to the position they had reached at that point would be manifestly unfair to those who were still speeding up and partial to those who were losing ground.
Color-naming, discrimination, cancellation, and coordination 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 a.n.a.lysis 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.
If it is true that with practice all tests correlate with one another, so that an individual who is good in one type of work is also, when his practice level has been reached, good in other types of work, the task of vocational psychology is at once enormously simplified. In place of further search for special occupational tests adapted in some peculiar way to particular types of work, our task is rather that of extending the general intelligence scales until they represent higher and higher degrees of general ability.
It is quite probable that further advance in this direction will come, not from the elaboration or invention of more tests, but by the selection of a very few tests, and the examination of the final limits of practice with respect to them. The problem will then be the selection of sets of tests in which initial performance shows high correlation with ultimate capacity in the tests themselves, or else the laborious and undramatic, but perhaps preferable, alternative of continuing every test until the practice limit is reached by the individual. In the latter case it would be well to learn more about the nature and range of these limits than we know at present.
In so far as particular tasks are actually found to call for highly specialized apt.i.tudes, for the detection of which tests are sought, there will be the further problem of correlating these various tests with the particular aptnesses or fitnesses toward the detection of which diagnosis is directed.
There will also be the problem of the alignment of the various types of work along the general intelligence scales, as rapidly as these are extended and elaborated. In so far as this method is followed, the task of selecting from candidates those best fitted for the accomplishment of special types of work will be easily handled. Vocational selection will readily find methods suited to its purposes. But vocational guidance, as distinguished from vocational selection, must for some time to come depend largely on the determination of interests, incentives, satisfactions, emotional values and preferences, and the discovery and direction of these through general channels of information and through the methods of industrial and pre-vocational education.
This is a hard and an arduous program. It calls for strenuous work on the part of investigators, patience and faithfulness on the part of observers, and wide cooperation of investigators with each other. From the immediately practical point of view it also offers an inviting opportunity to those foundations and individuals who are interested in supporting the further development of "the arts of social control over human nature."
FOOTNOTES:
[16] For explanation of the technique and meaning of correlation see the footnote on p. 45.
CHAPTER XII
CONCLUSION
The leading problems of vocational psychology we have seen to be three in number: First, how may the individual achieve the most adequate knowledge of his own peculiar mental and instinctive const.i.tution, his equipment of capacities, tendencies, interests and apt.i.tudes, and the ways in which he compares, in these respects, with his fellows? Second, how may the individual acquire information concerning the general or special traits required for successful partic.i.p.ation in the various vocations, in order to select a line of activity for which he is const.i.tutionally adapted? Third, how may the employer determine the relative desirability, fitness and promise of those who may offer themselves as his a.s.sociates and a.s.sistants, or for minor positions in his employ? Obviously, if vocational psychology were in its maturity, rather than in its infancy, these various questions would resolve themselves into a single problem. The traits required in the various types of work would be fully known and specified, so that both the choice of the individual and the selection by the employer would proceed directly, once the individual"s characteristics were known.
From this goal we are very far, but by no means hopelessly, removed. As we have seen in the preceding chapters, the line of attack is being advanced very unevenly at its various points. It is indeed characteristic of any new branch of science that it does not advance symmetrically and at a uniform rate, but moves ahead, now in this direction, now in that, so that the line of complete development is some distance behind the outposts of exploration. So in the case of vocational psychology we may draw a rough line which shall represent the main region of advance, and may indicate the various points where the line lags behind or goes conspicuously forward.
The main line of advance has left far behind it the magical ritual of primitive thought, the medieval search for significant omens and clairvoyant signs, the pseudo-scientific faith in the structural characteristics elaborated in physiognomy and phrenology, and has taken its stand firmly at the point where emphasis is laid on the objective study of the individual"s behavior. Educationally this position shows itself in the abandonment of the purely disciplinary ideal of abstract training, and the subst.i.tution of training in specific forms of conduct, exercise, and occupation, accompanied by concrete experience with industrial opportunities, rewards, and satisfactions. From the more strictly psychological point of view the position shows itself in the experimental application of mental tests. In the measurement of the more strictly intellectual capacities, the line has shown a very decided advance since the beginning of the present century. The available intelligence scales make possible the diagnosis of intellectual defect, normality or precocity in units of considerable reliability, in the case of pre-adolescents. This step in itself is sufficient to put educational, industrial and social enterprise deeply in debt to the new science of experimental psychology.
But this by no means const.i.tutes the only point of marked advance. Thanks to the elaboration of more complex and more diversified tests, and the gradual acc.u.mulation of norms, it is now possible to make mental measurements in the case of individuals considerably beyond the age of adolescence. By means of such methods, degrees of sensitivity, dexterity, accuracy, speed, comprehension, docility, discrimination, ingenuity, information, observation, and numerous other general aspects of mental alertness may be recognized. Comparison of such measures, in the case of adult workers with actual success in the field of their activity, tends constantly to show high degrees of positive correlation. The fact that the correlations are not perfect raises numerous problems, the solution of which is now being attempted.
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 const.i.tute 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, compet.i.tion, 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 apt.i.tudes, 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.
Another difficulty encountered at this point is the fact that such direct measures of vocational success as have been utilized in these comparisons are in themselves subject to very large error. Only in recent years, and as a result of the emphasis of the human factor in industry, has it come to be the common practice to secure adequate records of the work of the individual as contrasted with the work of the gang. Even today such records are available in accurate form for only the simpler operations, in which standardized conditions of work can be maintained. The relative success of salesmen, for example, is not fairly measured in terms of the amounts of their sales, the number of prospects interviewed, or the frequency with which the a.s.signed tasks are accomplished, unless the local trade conditions of the respective territories are fully taken into account.
Inasmuch as such errors of measurement tend to reduce the apparent correlation between the traits measured, it is extremely probable that the psychological tests are even more significant than their present results indicate. Refinement of the tests must be accompanied by more accurate and precise measurement of the actual working efficiency of individuals in the industrial field, if the results of the one are ever to represent the amount of the other. In this as in many other respects, the development of vocational tests depends as much upon the active and intelligent cooperation of industrial concerns as it does upon the enthusiasm and diligence of the psychological investigators.
From the point of view of the employer, the incompleteness of the correlation between tests and direct measures is of little concern. Even a very small positive correlation affords him a degree of guidance in the selection of his workers that was far from forthcoming under the haphazard methods of employment that have been traditional. But from the point of view of the individual who is seeking guidance, or who is accepted or rejected on the basis of his performance in psychological tests, any correlation which is imperfect may lead to occasional injustice and misdirection.
The diagnosis of the instinctive and att.i.tudinal characteristics and the recognition of the more specialized apt.i.tudes const.i.tute two points at which the line of advance is relatively slow. It is at these points that the psychographic methods find their task. As we have already seen in detail, the methods of the individual and the vocational psychograph are still in the stage of empirical procedure. In this stage of their development nearly any effort to amplify or apply them is certain to contribute results of positive value. The recent studies that have contributed most notably toward the further development of the psychographic technique have been in the form of the specialized vocational tests and methods. Such studies, in addition to yielding results of immediate applicability in the description and a.n.a.lysis of the special tasks at which they are directed, also const.i.tute positive progress towards the more elaborate psychographic pictures of individuals and of tasks.
Meanwhile groups of further problems have been definitely organized, and preliminary steps taken toward their solution. The formulation of systematic guides to self-a.n.a.lysis and introspection and the study of the reliability to be placed in the individual"s estimates of his own characteristics are making definite and interesting progress. The examination of the time-honored "recommendation" and the estimates of a.s.sociates and friends, and the investigation of the accuracy of such judgments as are based on these testimonials, on letters of application, on the school records, etc., have already thrown long-desired illumination on several aspects of vocational psychology. The effort to base the vocational endeavors of women on the data of exact inquiry, rather than on the maintenance of primitive taboos and domestic and literary traditions, has played its own valuable part in one of the most vital economic adjustments of our age.
The very fact that a systematic presentation of the problems and methods of vocational psychology is possible signifies an enormous advance beyond the very recent stage in which all vocations were mysteries, all choices a serious form of gambling, and all employment confessedly a matter of impressionistic prejudice. To those who become familiar not only with the program of this new branch of applied science, but as well with the outstanding definite and positive contributions which that program has already yielded, the words of a constructive pioneer in this branch of scientific inquiry seem to be already becoming a statement of fact, rather than the mere expression of a hope. "The nineteenth century witnessed an extraordinary increase in our knowledge of the material world, and in our power to make it subservient to our ends; the twentieth century will probably witness a corresponding increase in our knowledge of human nature, and in our power to use it for our welfare."
APPENDIX
CLa.s.sIFIED BIBLIOGRAPHY FOR VOCATIONAL PSYCHOLOGY
1. MOTIVES OF VOCATIONAL PSYCHOLOGY