FOOTNOTES:[14]The series of tests proposed, and an especially clear discussion of the problems, methods and characteristic results of these tests, is to be found in Science, Jan. 24, 1913, pp. 133-142, in Thorndike's article on "Educational Diagnosis."
[14]The series of tests proposed, and an especially clear discussion of the problems, methods and characteristic results of these tests, is to be found in Science, Jan. 24, 1913, pp. 133-142, in Thorndike's article on "Educational Diagnosis."
[14]The series of tests proposed, and an especially clear discussion of the problems, methods and characteristic results of these tests, is to be found in Science, Jan. 24, 1913, pp. 133-142, in Thorndike's article on "Educational Diagnosis."
It is customary for authors, in discussing vocational problems, to assume that the vocational future of girls is determined in advance by the fact of sex. Not infrequently the lack of provision for domestic training in our high schools and colleges is indicated at length, and suggestions for establishing the domestic arts and sciences on a firmer basis in the educational system are advanced. Some paragraphs may be devoted to a discussion of the statistics which show that thousands of girls go from school into industry, and to an inquiry as to what training is best fitted to assist them in earning a living for the period intervening between graduation and matrimony. With this the discussion of vocational problems ends, so far as girls are concerned, and the remaining space is given over to more adequateconsideration of the vocational aptitudes and guidance of boys.
It is the purpose of this chapter to inquire whether there are any innate and essential sex differences in tastes and abilities, which would afford a scientific basis for the apparently arbitrary and traditional assumption that the vocational future of all girls must naturally fall in the domestic sphere, and consequently presents no problem, while the future of boys is entirely problematical, and may lie in any one of a score of different callings, according to personal fitness. We shall try to determine whether the present expectation that all women will follow the same vocation, i. e., housekeeping, is founded on any fact or facts of human intellect, or whether it arises merely from ideas of traditional expediency connected with the care of the young, and whether it leads to a waste of energy and of intellectual talents.
The discussion will take the form of five general questions, together with the answers which are to be made to each in the light of experimental psychology: (1) Are there innate sex differences in average intelligence? (2) Is either sex more variable than the other in mental traits? (3) Are there any special causes of intellectual inefficiencyaffecting one sex but not the other? (4) Are there any sex differences in affective or instinctive equipment which would naturally lead to vocational differentiation of the sexes? (5) What explanation is to be given of the traditional division of labor between the sexes?
It will be necessary at the outset to draw a clear distinction between theliterature of opinionand theliterature of fact. The literature of opinion includes all written statements, made by scientific men and others, not based on experimental evidence. The literature of opinion on the subject of sex differences in mental traits is voluminous. It appears in the writings of Nietzsche, Schopenhauer, Mill, Möbius, and others. By the literature of fact is meant those written statements based on experimental data, which have been obtained under carefully controlled conditions, and which may be verified by anyone competent to understand and criticize them. In this chapter we shall seek the answers to the propounded questions in the literature of fact alone, neglecting as irrelevant to the discussion the entire literature of opinion.
Since the discussion is limited to the literature of fact, it will of necessity refer only to literature of a comparatively recent date. Until about fifteenyears ago there had been practically no attempt to collect precise data on the subject of sex differences in mental abilities. Before experimental data were sought the hypothesis was accepted that human females are, by original nature, different from and inferior to human males, intellectually. The factor of sex determined everything; the way to discover whether a given individual was capable of any given intellectual task was not to let the individual undertake the task and to judge by the result, but to indicate the sex of the person in question.
Coincident with the intense controversy which rose in the nineteenth century over the higher education of women, a number of statistical studies were carried on by the questionnaire method. These were followed by experimental studies, and at the opening of the twentieth century several experiments were being made to investigate the matter of sex differences in intellect. About this time also the idea began to gain headway that whatever differences exist between the sexes as we find them in the world may be due to training and not to original nature; and it began to be pointed out that this aspect of the matter complicates even experimental investigation in ways difficult to control.
We may speak here of the experiments on brain weight which were published and much discussed about thirty years ago. Romanes, among others, insisted that the male brain was, on the average, several grams heavier than the female brain, and for a time it was supposed that the fact of innate female inferiority had been thus satisfactorily established. However, it was later demonstrated that relative to total body weight the female brain is as heavy as the male brain. It was also found that no positive correlation can be established between brain weight and intellect.
In 1906 Helen Bradford Thompson published her dissertation, from Chicago University, entitled "The Mental Traits of Sex." This volume gives a summary of the scattered bits of experimental work done previous to that time, and presents her numerous experiments on a group of men and a group of women at Chicago University. The result of her tests in various mental traits is that the differences between the sexes were in no case as great as the individual differences within either sex. Men differed from each other in these experiments (as did women also, among themselves), as much as men differed from women. In only two of the many traits tested was a reliable difference found between the central tendencies ofthe sexes. In speed of voluntary movement (tapping) men were quicker than women, and in memory women were superior to men. On the whole, however, the result indicated equality of mental ability between the sexes.[15]It will be enough for the present purposes to say that after about twenty years of collecting data by scientific experiment, the hypothesis that there is any innate sex difference in average intellectual ability has been abandoned by all psychologists who base their statements on scientific evidence. For example, Dr. E. L. Thorndike, in the most recent edition of "Educational Psychology" (1914), writes as follows, in summing up the experimental work on sex differences in average intellectual ability:
"The most important characteristic of these differences is their small amount. The individual differences within either sex so enormously outweigh any difference between the sexes that for all practical purposes any such difference may be disregarded.... As is well known the experiments of the past generation in educating womenhave shown their equal competence in school work of elementary, secondary and collegiate grade.... The psychologist's measurements lead to the conclusion that this equality of achievement comes from an equality of natural gifts, not from an overstraining of the lesser talents of women."
Thus our first question, Are there innate sex differences in average intelligence, which would call for differentiation of vocations on the ground of sex? may be thus answered: So far as the literature of fact tells us, we know of no considerable sex differences in average mental ability. The evidence of experimental science (and on this point there is now a large amount of evidence available) shows that by the test of averages the sexes have equal ability to perform mental tasks.
Our second question, Is there a sex difference in variability in mental traits which would call for a differentiation of vocation on the ground of sex? has not been so long, nor so thoroughly investigated by experimentalists as has the first question. What we are trying to discover here is whether, when tested in any given mental trait, a group of boys will differ more from one another than will a group of girls (similarly selected and equal in number) differ from one another. In other words, are the members of one sex verymuch alike in tastes, interests and abilities, while the members of the other sex differ over a wide range of tastes, interests and abilities? Obviously this might be the case, though the two groups yielded an average exactly the same in such traits. The answer to this second question will be of decided significance for vocational guidance. For example, if it were shown by experimental data that human females are, by original nature, rather closely alike, whereas human males differ from one another by wide extremes, we should have scientific grounds for concluding that social justice and social economy are well served by the present policy of guiding all females into a single occupation, while males are encouraged to enter the greatest possible variety of callings.
The first discussion of the comparative variability of the sexes was broached about a century ago by an anatomist, Meckel. It is very interesting (as well as amusing), in view of subsequent ideas about variability, to note what Meckel said. He thought the human female to be more variable than the human male, and he opined that, "since woman is the inferior animal and variability is a sign of inferiority," the conclusion was justified! Fifty years later, when Darwin put a different face upon variability, showing it to be an advantageand a characteristic affording the greatest hope for progress, the greater variability of the male began to be affirmed everywhere in the literature of opinion. Karl Pearson alone took issue with this view, which was current in the nineteenth century and is still widely credited, and pointed out that there existed as yet no literature of fact regarding comparative variability (though men of science had not on this account restrained themselves from uttering the most positive statements concerning it). Pearson thereupon actually gathered and computed hundreds of measurements of human beings, and presented his results in 1897, in a comprehensive article entitled "Variation in Man and Woman." He clearly demonstrated that there is, in fact, no indication of greater male variability, when actual anatomical measurements of adult human beings are treated with mathematical insight. Immediately Havelock Ellis, whose opinions were chiefly affected by Pearson's article, replied that when adults are made the subject of investigation, no information is gained regarding the matter of inherent or original differences in variability. Since birth, life and death, on account of social customs, etc., affect the sexes unequally, no one can say, in the case of adults, how much may be due to environment and how much to originalnature. If Ellis had thought of this criticism before he wrote his own book, "Man and Woman," his chapter on "The Variational Tendency of Men" would certainly not have been published. However, his criticism of Pearson's material is no less just because he failed to apply it in his own case. It is true that measurements of adults do not tell us what might be the case with infants, who have not yet been subjected to the formative and selective influences of environment and training. Yet Pearson's article remained practically the only literature of fact regarding the comparative anatomical variability of the sexes until the year 1914. In 1914 Montague and Hollingworth published in theAmerican Journal of Sociologyan article setting forth in full the measurements of two thousand new-born infants, one thousand of each sex. The statistical result shows no difference whatever in variability between the sexes.
It may seem irrelevant to dwell upon anatomical data, when the purpose of this chapter is to deal with mental aptitudes. The pertinence of the data cited, however, lies in the fact that if any sex difference in physical variability could be established, this would suggest (though it would not prove) the existence of a sex difference in mentalvariability also. No experimental studies have ever been made for the express purpose of determining whether there exist sex differences in mental variability. Such scattered data as we possess have come incidentally from studies made with some other chief purpose in view. Such data were collected and summarized in theAmerican Journal of Sociologyfor January, 1914. There was at that time very little evidence that could be cited on this subject, but such as there was gave no ground for maintaining the existence of any sex difference in variability. Since 1914 Trabue's experiments, with "completion tests," performed on about 1,300 school children, have been published; the Courtis arithmetic tests on several thousands of school children in New York have been made public; Terman has tested 1,000 unselected children by the Binet-Simon tests; and Pyle has undertaken his study in the measurement of school children. The evidence from these extensive experiments is in all cases that there is no sex difference in mental variability, as thus measured.
It is necessary also for the reader to bear in mind that there is as yet much controversy among those best equipped to understand the problems of variation, as to the proper methods of measuring comparative variability. The mathematicalconsiderations involved need not be rehearsed here. But until it has been definitely determined just how comparative variability can be scientifically measured, it would seem premature to make any final statement as to sex differences in this respect.
We can therefore answer our second question thus: There is little or no agreement among those best qualified to speak, as to what constitutes the scientific method of measuring comparative variability. But according to the methods now deemed the most reliable, and according to those studies wherein presumably correct methods of measurement have been employed, there is no reason to suppose that there is any sex difference in variability, so far as the numerous traits tested are concerned. There has never been an experimental study made in which the sampling from both sexes was large, random, equal, and from groups of equal homogeneity socially and racially, that showed any reliable sex difference in variability. If we adhere to the literature of fact, we must conclude that, so far as we know, human females differ from each other as much as do human males in abilities and aptitudes.
We now come to the inquiry as to whether there are any special causes of intellectual inefficiencywhich affect one sex but not the other. Under this topic we may consider the periodic function, which characterizes girls and women, but which does not characterize boys and men. This periodic function has always been the object of superstition and taboo, and is such even among the civilized peoples of today. The literature of opinion is replete with references to it as a source of intellectual weakness and irresponsibility. We may let Frederick Harrison speak for a large group of writers on this point:
"Supposing all other forces equal, it is just the percentage of periodical unfitness which makes the whole difference between the working capacity of the sexes. It is owing to a very natural shrinking from hard facts, and a somewhat misplaced conventionality that this fundamental point has been kept out of sight."
The literature of opinion abounds in different notions, inconsistencies, and contradictory instances in the matter of the periodic function, and its alleged enormous influence on the intellectual and vocational life of women. Much of the opposition to the education of women was based on it, and it has even been exploited as a good reason why political freedom should be denied to women. It is positively stated that women are on this accountunfitted to pursue professional and commercial life; yet it is not proposed that cooks, scrub women, mothers, nursemaids, housekeepers or dancers should be periodically relieved from their labors and responsibilities.
There is almost no literature of fact concerning the periodic function as related to the mental abilities of women. No effort had ever been made to subject this matter to study by instruments and methods of precision until very recently. Psychologists, while often stating the influence of periodicity on mental life to be fundamental and characteristic, entirely neglected to consider it when performing experiments on women subjects. In 1909 Voitsecovsky, at Petrograd, performed an experiment on six women by means of instruments of precision. He thought he found a positive result and that there was shown to be an actual influence of periodicity on certain mental functions. His conclusions are, however, largely invalidated by the fact that all his subjects knew the purpose of the experiment, and by the fact that he neglected to use, as a control, human beings not subject to the phenomenon in question. He also neglected to present his data in full, so that the reliability of his conclusions might be calculated.
Two studies of this phenomenon appeared in1914. The first was a study by Dr. A. E. Arnold, as to the effect of school work on the periodic function, and this is reported in the January number of theAmerican Physical Education Review. This investigator suspected, from his experience as a physician and teacher, "that much of the incapacity claimed was fictitious," and he determined, as an experiment, to institute a régime whereby no student under his supervision would be excused periodically from mental or physical duties, except in cases where some pathological condition existed. In summing up the data he says: "So far our results show all improvement [in the health of students]."
The second study, which appeared in 1914, was by the present writer. She made a prolonged and careful experimental study of twenty-three women (using as a control the records of men subjects), and failed to demonstrate any influence of periodicity on those mental abilities which she tested. These included speed and accuracy of perception, controlled association, steadiness, speed of voluntary movement, fatigability, and rate of learning.
A great amount of scientific work remains to be done before any final answer of any kind can be given to the question, Does functional periodicity exercise a fundamental and characteristic influenceon the intellectual abilities of women? We must answer our third question in this way: There is very little experimental evidence on which to base a reply, but the few data which we do possess show no influence, either detrimental or beneficial.
Our fourth inquiry is this: Are there any innate sex differences in affective or instinctive equipment that would naturally lead to a vocational differentiation of the sexes? Here we must acknowledge ourselves to be entirely without a literature of fact. The literature of opinion is very extensive on the subject, and it would be an interesting and no doubt an instructive task to collect and summarize the various and conflicting opinions of men as to the affective and instinctive differences between the sexes. Men and women as we see them in the world do differ in affective behavior, but no one can say whether these differences in behavior are original or acquired. There are different conventional standards of emotional behavior for men and for women, but no one would be justified in saying that such standards arose from inherent affective differences between the sexes. The very variety that characterizes the statements on this subject constitutes proof of the ignorance of mankind in regard to it.
Since exact data are entirely lacking, the discussion of this last question need not detain us. We may, however, glance at one instinct which has repeatedly been stated to characterize women, and to constitute in itself a natural justification for differentiating the sexes vocationally. This is the "maternal instinct." Since the period of helpless infancy is very prolonged in the human animal, and since the care of infants is an exacting and onerous labor, it would be natural for those who are not biologically attached to infants, to use all means at their disposal to fasten the whole burden of infant-tending upon those who are originally so attached. We should expect this to happen, and it does happen. There has been a continuous social effort to establish as a norm the woman whose vocational proclivities are completely and "naturally" satisfied by child-bearing and child-rearing.
In the absence of all data, it would seem most reasonable to suppose that if it were possible to obtain a quantitative measurement of "maternal instinct," we should find this trait distributed among women just as we have found all other traits distributed, which have yielded to quantitative measurement. It is most reasonable to assume that we should obtain a curve of distribution,varying from an extreme where individuals have a zero or negative interest in the care of infants, through a mode where there is a moderate amount of impulse to tend infants, to a second extreme where the only vocational interest lies in such activity. The bearing and rearing of children is in many respects analogous to the work of soldiers. It is necessary to national existence, it means great sacrifice of personal advantage, and it involves suffering and danger, and, in a certain percentage of cases, the actual loss of life. Thus, as in the case of soldiers, every effort is and must be made to establish as a norm the extreme end of the distribution curve, where there is an all-consuming interest in patriotism, in the one case, and in motherhood in the other. In the absence of all scientific data, we should, therefore, guard against accepting as an established fact about human nature a doctrine that we might expect to find in use as a means of social control. It is also fitting to raise the question as to just what is meant by the term, "maternal instinct." Does it mean desire for offspring which are as yet non-existent? Does it mean only the tendency to care for helpless offspring after they are actually in existence? Does it mean an interest in children as such, regardless of their origin? Or does it consist in amingling of all these elements? Above all, does it involve, as an essential element, an interest in waiting personally upon infants? One certainly gains the impression from a perusal of the extensive literature of opinion that to most persons the term is quite unanalyzed, and that it calls for analysis.
We have now considered four of our inquiries in the light of experimental evidence. We have discovered that a great amount of work remains to be done before we can answer most of them conclusively, and that to one question, at least, no answer at all can be given from the literature of fact. We can only say that, so far, scientific experiment has revealed no sex differences in the original nature of intellect that would imply a necessary differentiation of vocations on the ground of sex. There exist no scientific data to show (1) differences in average intellect; (2) differences in mental variability; (3) special causes of intellectual inefficiency affecting one sex but not the other; (4) differences in affective or instinctive equipment, implying a "natural" division of labor.
The division of labor between the sexes, which has existed through historic times and still persists, originated, so far as we know, in physiological,not in psychological differences. The momentous physiological fact that women bear and nourish infants and men do not, is the great primary sex difference on which our economic and vocational organization has been built up. It might be supposed that natural selection would have evolved an intellectual (or unintellectual) type in women, which could find its complete natural satisfaction in the vocation of child-bearing and child-rearing. But such a selection could take place only if mental traits were sex-limited in inheritance, or existed as secondary sex characteristics. No mental trait has ever been proved to be sex-limited in inheritance, or to exist as a secondary sex character. So far as we know, daughters inherit mental traits from fathers as well as from mothers, and sons inherit them from mothers as well as from fathers. Under such circumstances the law of natural selection can never become operative to solve the vocational problems of women.
The fact that women have not in the past equaled men in "philosophy, science, art, invention and management" is frequently adduced as evidence of their innate unfitness for pursuits other than the domestic. From such evidence, however, we glean in reality no information whatever about the vocational aptitudes of women.We should not expect any notable achievement by women in the fields mentioned above, for the following reasons. Women must bear and nourish infants, and men cannot. The period of gestation and the period of infancy are very protracted in the human species, together covering, for each infant reared, about six years. Until very recently no scientific methods of controlling procreation have been generally known or utilized. Thus women have borne great numbers of infants, all their youth and maturity being consumed by bearing and rearing young. The small minority of women whose lives happened not to be so consumed would be very unlikely to make any contributions in extra-domestic vocational achievement for two reasons. In the first place, all women were expected to mate and thus to procreate and rear offspring, and no provision was made by society for their training in lines other than those they would be expected to use. In the second place, those women who did not meet the common fate failed to do so for some special reason, such as ill health, mental disease, or the necessity of caring for decrepit relatives. The very causes of their celibacy would operate also against any vocational achievement on their part.
In the irrational trial and error method bywhich our human institutions have been developed, the logical expectation would be that the great physiological sex difference in reproductive function would probably influence vocational activities just as it has done. We find in the traditional division of labor between the sexes exactly what we should expect to find, even though there were an identity of intellectual abilities and interests. It seems both psychologically and socially desirable that the one incontestable conditioning factor in the vocational differentiation of men and women be raised clearly to consciousness, rather than submerged, as in the past, by an elaborate system of defense mechanisms and traditional devices of social control. It would be going afield from the immediate purpose of this chapter to offer constructive suggestions for such changes in economic and domestic management as might be necessary to overcome this conditioning factor, and thus to give free vocational opportunity to both sexes alike. To effect these changes in such a way that the maximum social betterment may be achieved thereby will be a task not simple but complex. It will call for the best thought and the most enlightened effort of which we are capable, and will be accomplished only with the passing of years and decades.
The essential thing at present is to know whether any basis for future action may now be found in the established facts of human nature. In the present state of scientific knowledge it would be as dogmatic (and therefore as undesirable) to state that significant sex differences in intellect do not exist, as to state that such differences do exist. All we can say is that up to the present time experimental psychology has disclosed no sex differences in mental traits which would imply a division of labor on psychological grounds. The social gain would be very great if the public could be brought to recognize intelligently that to many of the questions regarding the vocational aptitudes of women no definite answers can at present be given, because the necessary data for the formulation of answers have never been collected. So far as is at present known, women are as competent intellectually as men are, to undertake any and all human vocations.
FOOTNOTES:[15]There was published in the October (1914) issue of thePsychological Bulletina summary of all important experimental work done on sex differences in recent years. Any reader wishing to take up the evidence greatly in detail will do well to consult all of the references there given.
[15]There was published in the October (1914) issue of thePsychological Bulletina summary of all important experimental work done on sex differences in recent years. Any reader wishing to take up the evidence greatly in detail will do well to consult all of the references there given.
[15]There was published in the October (1914) issue of thePsychological Bulletina summary of all important experimental work done on sex differences in recent years. Any reader wishing to take up the evidence greatly in detail will do well to consult all of the references there given.
The more general questions of the theory of tests, their selection, evaluation, and technique of application and record, need not be considered here. The reader unfamiliar with these matters will find them fully treated in the various standard manuals of tests, and in numerous special articles and monographs referred to in the bibliography.
There are, however, certain particular aspects of the theory and use of mental tests which have special importance for vocational psychology. These are:
1. The question of the degree to which proficiency in one respect or ability or test implies proficiency in others.
2. The degree to which these intercorrelations are revealed by preliminary trials and modified by continued practice.
3. The question of the significance of preliminary trials in revealing the relative abilities of individuals as these would be shown after all theindividuals had acquired their maximum skill or practice level of proficiency; that is, the relation between momentary capacity and ultimate achievement.
Attempts to intercorrelate mental or motor abilities as measured by laboratory tests have usually produced more or less irregular results. Some of the coefficients have been positive, some negative, but in only a few cases have many of them been large when the individuals tested have been chosen at random or with no deliberate intention of measuring only the extremes of the curve of distribution. Thus in a recent report of the correlations of abilities among several hundred adult individuals it is remarked that a certain test for logical memory is "one of the very best tests," partly because of "its high correlation with other tests" (an average correlation of .29).
Two reasons are largely responsible for these low coefficients. The first is the fact that the measures correlated have usually been initial trials, or at most averages of a very few trials. This means great individual variability and considerable consequent unreliability of the data. A more important factor, perhaps, is the fact that these preliminary trials do not necessarily representthe final capacities of the individuals. They are determined by a host of incidental or accidental influences and reveal only momentary ability, not ultimate capacity. There is every reason for expecting to find positive correlation of "desirable" traits, and we may well expect to find this increasingly true the more our measures test the final limits of capacity in the various tests. In other words, the only real correction for unreliable measures is to be made by continuing the test until the individual has reached the limit of practice in it.
Only occasional attempts have been made to determine the influence of practice on the correlation of abilities, and those that have been reported have been based on so few practice trials that no review of them need be given. In the present chapter I shall present the results of an experiment in which a group of observers were repeatedly tested until in each test a practice limit was approximated, a limit which, in most cases, one hundred further trials failed to improve. The results have a real interest for vocational psychology.
The experiment consisted in putting each of thirteen individuals through 205 repetitions of seven different mental tests. The trials were controlledas thoroughly as possible with respect to such factors asinterimoccupation, exercise, food, rotation of tests, temperature, illumination, and incentive and interest. The subjects, four women and nine men, ranging from eighteen to thirty-nine years in age, were mature, zealous, and faithful. Competition was stimulated by the award of desirable prizes, and each worker received a daily wage. Records were announced to the subjects only after each thirty-five trials. So far as previous practice in these particular tests is concerned, all the subjects were naïve. Five trials were made daily, these trials being distributed through the day at about two-hour intervals. The tests themselves occupied about forty minutes at each sitting.
The tests used were the following familiar laboratory forms:
1. Adding. Adding seventeen mentally to each of fifty two-place numbers and reciting aloud the correct answer. Order of numbers random at each trial. Record with stop watch, time required for perfect score.
2. Naming Opposites. Correctly naming opposites of each of fifty adjectives which occurred each time in random order. Record, time required for a perfect score.
3. Color Naming. The Columbia laboratory form of this test, with ten repetitions of each of twelve colors. Position of card changed at each trial. Record, time required for perfect score.
4. Discrimination Reaction. Discriminating between red and blue, and reacting correctly with appropriate hand. Record, average time, insigma, and number of false reactions.
5. Cancellation. Crossing out digits from the Woodworth-Wells form of this test. Record, time required for 75 correct cancellations of equally difficult digits.
6. Coördination. The familiar three-hole test, for accuracy of aim. Record, time required for one hundred correct strokes.
7. Tapping. Executing four hundred taps at maximal speed, with hand stylus, right hand, elbow support. Record, time required.
Each test has been correlated[16]with all the remaining tests at various points in the curve of practice. Correlations were made at each of the following points:
1.Preliminary trialdesignated1st trial2.Median of first 5 trialsdesignated5th trial3.Median of trials 20 to 25designated25th trial4.Median of trials 75 to 80designated80th trial5.Median of trials 200 to 205designated205th trial
At each of these points the thirteen individuals were arranged in an order of relative ability for each of the tests, and these orders were correlated with each other. Table 23 gives, for each test, at each point, the average correlation with all the other tests, and also the grand average correlations of all tests.
TrialAddingOppositesColor NamingDiscriminationCoördinationTappingFinal Average1.19.10.15-.07-.15.17.0655.41.26.15.35.21.32.28025.50.35.43.27.03.35.32080.55.43.53.31.18.34.390205.48.62.61.35.34.52.490
Except in the case of discrimination the effect of practice is to increase to a marked degree the intercorrelations of the various tests. Adding increases steadily up to the eightieth trial. Opposites and color naming gain even more steadily to the very end of the experiment, the increase in the coefficients being four to six fold. Tapping increases more slowly but no less certainly. In coördination the increase is very irregular, but the coefficients show, on the whole, a change from -.15at the first trial to .34 at the finish. Only in the case of discrimination is there failure to increase after the fifth trial. In no case, after the preliminary trial, is there a negative coefficient among the average correlations, and indeed in only one case is there a coefficient smaller than .15. The final averages show steady increase from .065 at the preliminary to .28 at the fifth, .32 at the twenty-fifth, .39 at the eightieth, and .49 at the two-hundred-and-fifth trials.With practice, then, the average correlations of all tests become positive, and the coefficients become greater the longer the practice is continued.
In producing this increase in the intercorrelation of specific abilities through the medium of practice, at least three different factors probably coöperate. These factors have not an equal significance for vocational psychology and its interests in tests.
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 ofthe 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 repetitions, to resemble more and more that type of process or function involved in color-naming. The responses become more and more intimately associated 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 association 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 analysis 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 repetition. 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 characterof 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 assumption 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, coördination and adding should show the same increase in correlation. Just the reverse is actually the case, the correlation of coördination 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 truersamples. 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 attitude and initial method of attack. They would, in short, be samplings only of momentary ability, not of final capacity.
Or if the assumption 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 tofinal capacityrather than tomomentary 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 typeof 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 eventuallyreach, 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 assumed 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 displacementin their relative order of ability are thus produced? At what point or points in the curves do the individuals assume 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: