The Range of Human Capacities
- Type:
Book Reviews
- Author:
David
Wechsler, Ph.D. Bailliere, Tmdall and Cox, London, 1935. 11/6.
I find this to be a stimulating, if not an important piece of work, and propose to give it a fairly exhaustive review. It is concerned, as the title states, with the range of human capacities. ” When we compare the mathematical ability of an Einstein, or the scientific intuition of a Pasteur or the poetic gifts of a Shakespeare, with the correlative abilities of average men, let alone those of a moron or idiot, the range of human abilities appears well nigh limitless.” Wechsler begins with these words, and then proceeds to ask how extensive these differences are. How much do the least and the most able individual differ?
Some few years ago Wechsler startled some of us by suggesting that the differences between individuals at most amounted to the important figure 2.7182…, namely, an amount equal to the logarithmic constant. This would seem to betray Wechsler’s own ability?some of us can see Wechsler searching unconsciously for perfection, here in a perfect, and yet also imperfect, constant. But this minor aberration on his part must not prevent us from paying serious attention to the present study, which indeed is a model of its kind, a valuable and almost exhaustive scientific study.
Wechsler’s method is to search all the literature available to him for satisfactory data upon which to apply his measurement of range. Some ninety major studies are investigated, with populations of 200 or so up to nearly 100,000 persons. He has many sound things to say about the paucity of published data; few of us now emulate the great Galton and work with thousands of persons as population. Fewer still report all the necessary data in their papers.
Wechsler, nevertheless, is able to draw upon measurements for such capacities as stature (96,239 American soldiers), span of arms (1,241 English females), body temperature, duration of pregnancy, platelats in the blood, neck circumferences, respiratory rate, pulse rate, weight of brain, heart, hair, and kidney, and similar physical and physiological measurements, as well as upon abilities of the kind tapping, stringing discs, running 60 metres, card sorting, memory span, intelligence quotient, and formboard ability.
As his measure of range he uses the ratio between the ability of the 2nd and the 999th person in each 1,000 individuals. These extremes of stature in the case of the American soldiers are 152.6 and 164.9 cm. respectivelyThe range is, therefore, 164.9 divided by 152.6, an amount 1.28. The following figures give examples of such ranges, taken from the ninety or so reported by Wechsler:
Body temperature … … 1.04 Calcium in blood … … … 1.26 CO2 production per minute … 1.54 Neck circumference … … 1.53 Pulse rate … … … … 1.86 Body weight … … … 2.44 High jump 2.02 Card sorting … … … 2.50 Intelligence quotient … … 2.30 Hard learning … … … 3.81 (Substitution test) The most striking thing about such ratios _lS certainly their smallness, and also the way i11 which they increase with increasing complexity of the capacity or ability.
Wechsler supports his criterion of range, the face of current opinion that a measure in terms of extreme values (such as the 2nd and 999th in a 1,000 population) is likely to be unsound. He points out, and quite rightly, that very little if any data such as he has examined is distributed on a normal probability curve, s? that he is not justified in using sigma as measure of range. By omitting the 1st and 1,000th case in each 1,000 Wechsler believes that he takes sufficient account of such errors as the extremes involve. I am inclined to agree with Wechsler, that for his purpose his unorthodox* but simple and apparently efficient, statistical device is permissible. It results in a remarkable orderliness in the ratios it supplies. These, the above samples show, range from about 1-2” to a little over 3.00. Moreover, the ratios seenj to be clustered; more ratios than we would anticipate by chance are of values 1.26, 1-^’ 2.00, and 2.52 respectively?and these value5 are successively 1.26, 1.262, 1.263, and 1.26; Whether this latter geometricity is another oI Wechsler’s unconscious searches for perfection, now replacing his earlier conjecture 2.7182 . ? ‘ (e), I am in some doubt. Philpott has sho^11 just such remarkable instances of geometric ratios in his study on ” Fluctuations in Human Output ” (British Journal of Psychology’ Monograph Supplement XVII), and it would W an extraordinary fact if this same kind 0 geometricity appeared in gross abilities anC growths of the human being.
Having admitted the validity, to my mind, of the statistical procedure, it remains to interpret the results and to examine whether they are Really exhaustive. Since the ratios are so small, Wechsler proceeds to infer that individuals do u?t differ as much one from another as is usually believed. In this connection, too, he examines at length the growth of abilities with age, and jlecides that man is at his maximum ability between the ages 20 and 35 or so. Here, indeed, Wechsler waxes extremely pessimistic. He calls the Chapter ” The Burden of Age “, and it flakes funereal and dismal reading. He shows that men of genius have usually given their best ^v?rk to the world before they are 40; he repeats the notion that intelligence ceases to grow at about 15 years of age. Yet he has to admit that experience and maturity count for somehing, and that it is stupid to suggest that youth should be put at the helm because of its superior Opacities. It may be true that the ideas that jjvify a nation or a science or an art come for the main part from the younger individuals rather than from the old, but it needs the sanity aud maturity of the older, their judgment and Perspective, to place these ideas on a charitable aud reasonably conservative footing.
His discussion of genius leaves much to be desired. He considers that the genius and the fuperior person differ very little in capacity, ut that this slight difference leads to the vast Qualitative and quantitative differences in outPut that marks the man of genius as a being aPart from the merely superior person. Genius ls believed to depend on the ” rare ability to Perceive new relationships ” (p. 77). The truth Seems to be, however, that the ability to perceive Uew relationships is by no means rare, but is lristead one of the most common of human Abilities. In searching for something sui generis the genius it seems to me that Wechsler conradicts the main thesis of his study. For 1 |v?uld agree with Wechsler that the ranges of uuman capacities are not as wide as we imagine hem to be; and that as a consequence we lesser ut perhaps still superior mortals need not fear 0 attempt the task of becoming great mathematicians, physicists, medical practitioners, pists, politicians, and what we please, because ^?h levels of attainment in any of these spheres a^e not beyond the capacities of most persons . sound training and good intelligence. There s too much acceptance of superior attainment s something that is unapproachable except by e gifted few, and far too little faith in our ?vvu capabilities. The sparks of a genius, the simple ideas of a Newton of a Freud, or of an Einstein, are not beyond the range of vast numbers of persons who little believe that they could have been capable of such flights.
All this, however, does not necessarily follow from Wechsler’s data. I am certain that Wechsler could have found facts very different from those he reports, had he looked further afield for them. Thus, in the case of the University College (London University) Entrance Examination, an intelligence test given each year to some 400 students, the range of scores is nearer 10.0 than 2.0. The 2nd and 999th individuals have scores 50 and 400 respectively, and this without any distorting of the crude facts. Make the range of persons wide enough, and this ratio can be heightened still further, to hundreds, and not merely 2.0. All depends on what one takes to be ” units of amount.” In the case I am referring to, the individuals only have a limited time to solve each question of the intelligence test; the really stupid person rarely gets one answer correct because he never has time enough to complete it; but the clever person succeeds in the 400 or more he attempts during the 2 hours of examination. We merely have to increase the time of the examination, and the number of test-units, and the difference between the brilliant and the stupid person becomes greater and greater. Thus, I fancy that all facts do not have the simplicity that Wechsler’s data displays. The facts hold true for the physical and physiological capacities, but the more certain the work becomes on the purely psychological side of man, the more likely does it seem that the range will be much greater than that reported by Wechsler.
Nevertheless, the author has to be complimented on bringing to completion a very sound piece of work, the result, I am sure, of many months of labour. It is well worth reading by all who take an interest in the measurement of human abilities. Many of his observations on the need for better measurement, on larger populations, are welcome reminders to working psychologists. It is no less necessary that all the facts of an experiment should be available for posterity, and not merely an average and a standard deviation descriptive of such facts. In this connection it is of interest that the Council of the British Psychological Society has recently instituted a Committee on Human Mental Measurements, which has as one of its objects the husbanding of just such masses of data as those so diligently sought for by Wechsler. Wm. Stephenson.
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