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Intelligence, learning, and evolution; a noteC. J. Borthwick aa Assistant to the Secretary, University Assembly , University of MelbournePublished online: 26 Jan 2010.
To cite this article: C. J. Borthwick (1979) Intelligence, learning, and evolution; a note, Melbourne Studies in Education, 21:1,174-182, DOI: 10.1080/17508487909556133
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INTELLIGENCE, LEARNING, ANDEVOLUTION; A NOTE
by C. J. BORTHWICK
In Professor Arthur R. Jensen's The Nature of Intelligence andits Relation to Learning' (Melbourne Studies in Education 2978)some seven pages are devoted to an attempt to show that 'in-telligence' or 'general mental ability' can be identified with whatis known as the g factor, a product of the factor analysis ofcorrelations between a number of 'intelligence' tests. The theoryis that all intelligence tests produce slightly different results be-cause each one is contaminated to some extent by irrelevant fac-tors, and these factors are not constant; but if one can analysewhat all the tests test for in common that will be 'intelligence',expressed as g. Many critics of intelligence testing, however, haveheld that the common factor between the tests is an illusion,that the correlations between the tests and the g these produceare only products of the way the tests are constructed—that thepsychologists are finding the proof that they have themselveshidden there. Tests are designed to correlate with other tests;
substantial correlations of items with tests as a whole [and,mutatis mutandis, between the test as a whole and other tests]are built in by simply eliminating items and subtests whichhave low correlations with the test as a whole and includingitems which would otherwise be highly suspect (e.g. Wechs-ler's information test) because they have a high correlationwith the test as a whole. Terman and Merril state flatly: Teststhat had a low correlation with the whole were dropped evenif they were satisfactory in other respects.' (Stanfora-Binet In-telligence Scale, p. 33)1
Similarly, Professor Jensen himself says 'If a test item is not sig-nificantly loaded on g (i.e. the first principal component) itdoes not measure what we mean operationally by intelligence and
1 N. Block and G. Dworking, The IQ Controversy (New York, Pan-theon Books, 1976), p. 463.
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should be excluded from any test so labelled'.2 The deck has beenstacked in favour of g.
In order to show that the measurements taken in intelligencetests have some relation to an inherent quality of the mind ofthe person being tested it. is necessary to connect them to a thirdthing capable of independent measurement—a criterion variable.Tests have been supported by showing that they were linkedwith—that they correlated with—success in school, income, orsocial position. Correlations of a greater or lesser extent can bedemonstrated in all these areas. All these measures, however,introduce new difficulties. The relation between correlation andcausation is not clear. Does a high IQ lead to high income, or—something approaching the reverse—does the IQ test measure thequalities displayed by the well-off? I have not space here to gointo the arguments dealing with these relationships in any detail,and mention them only to show how useful it would be for apsychometrician to be able to produce a scale that was clearlyindependent both of the social prejudices of the test designer andthe societal complications of the testee. Professor Jensen believeshe has found such a scale in the phylogenetic hierarchy. Themistaken notion that the g measured by intelligence tests residesin the specific item content and is therefore only an index ofculture-specific learnings is most strongly contradicted by thestudy of the evolution and phylogeny of intelligence.'3
An examination of his thinking in this regard must begin withan agreement to correct one crude error. Professor Jensen usesthe term 'phyla' throughout as though it were equivalent to'species'—'the degree of complexity and abstractedness of whatcan be learned, given any amount of time and training, showsquite distinct differences between phyla'.* A phylum is, after thedivision into the animal and plant kingdoms, the largest gradein the taxonomic hierarchy. Has any work been done on the com-parative intelligences of such phyla as blue-green algae and slimemoulds? All the examples Professor Jensen cites come from theVertebrata, a subphylum of the phylum Chordata. That difficultycleared aside, the argument to evolution is that
(i) the phylogenetic hierarchy corresponds in its order to
2 A. R. Jensen, 'The Current State of the IQ Controversy', AustralianPsychologist, vol. 13, no. 1, March 1978, p. 11.
3 A. R. Jensen, 'The Nature of Intelligence and its Relation to Learning',Melbourne Studies in Education 1978, p. 117.
4 Ibid., p. 119.M
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(ii) the position of the species on a scale of its success at in-creasingly g-rated tasks, which in turn corresponds to
(iii) the order of intelligence in which animals are placed byvirtually universal consent (of humans), and that there-fore
(iv) 'The g factor is thus not just peculiar to individual dif-ferences among persons within a particular culture, butis continuous with broader biological aspects of neuralorganization reflected, as well, in individual differenceswithin other primate species, and even in the evolution-ary differences in behavioural capacities between variousspecies. In this sense intelligence is as much a biologicalreality, fashioned by evolution, as are the morphologicalfeatures of organisms."5
Evolution has been used to reify intelligence (and if calling in-telligence as much a biological reality as a thumb does notreify it, it is difficult to think of a form of words that would).
The trouble with this argument is that it does not consist ofthree premises and a conclusion; it is one premise four times.
There is no such thing as a 'phylogenetic hierarchy* in the sensethat Professor Jensen appeals to. There is no such thing as a'phyletic scale* or 'phylogenetic statuses' or 'phyletic level' ex-cept as a convenience for scientists. The study of phylogeny isdesigned to establish the relations of descent between species—when species diverged from a common ancestral root, how theyhave developed since, what processes produced the features dis-played by each species now. When phylogeny is reduced to adiagram it is characteristically expressed as a tree showing thebranching lines of descent and, as with a tree, it is pointless toexpect continuity between the ends of the branches, let aloneranking. Professor Jensen seems to regard it as if it were some-thing more akin to a ladder, as if there were a single line ofdescent and fish were a less evolved form of birds, birds of rats,rats of cats, and so on. It is possible with more or less certaintyto calculate when each phyla, class and species diverged fromthe line of common descent; unsurprisingly, those that divergedfrom the line of humanity recently resemble us more than thosethat went their own way from the beginning. It is also certainlypossible to arrange a selection of species in the order of then-neurological complexity; but that is all that you are doing whenyou do that. You are not describing the shape of nature.
5 Ibid., p. 120.
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If Professor Jensen's scale existed it would be possible to ex-plain the fact that fish have smaller brains than men by then-relative position on the scale. This is not the way natural selec-tion works. Morphological characteristics, and convergence anddivergence between species, develop in response to the demandsof different environments. It makes little sense to rank diemas if they were all attempting the same thing with more or lesssuccess. Writers on evolution can talk of higher forms succeed-ing lower forms of the same genus because there is continuitybetween earlier forms and those to which they give rise. Ourancestors were closer to the primordial protozoa, were the resultof a shorter period of development, and have been preserved inlower geological strata. The same considerations do not apply tocomparisons between existing species, where the use of "higher'and lower' represents no more than an understandable anthropo-morphism, grading species by their nearness to us.
Moving on to the order Professor Jensen feels is established bythe tests he refers to ( I t is possible to give such diverse speciesas fish, birds, rats, cats, dogs, monkeys, and apes essentiallyequivalent forms of the same test problems')6 we note that theprocess of establishing that the tests are g-loaded is a complexone. Since no reliability coefficient has been calculated on alarge number of tests administered to a representative popula-tion of fish, g cannot be indicated directly. It is inferred from thetests because
For example, both normal children and children with varyingdegrees of mental retardation have been given the battery oftests that Kohler used with chimpanzees. Exactly the same rankorder of difficulty of these problems emerged for human chil-dren as for chimpanzees and lower primates (Viaud, i960,pp. 44-5). The complexity factor common to these experimentalanimal problems, that differentiates species of primates, rank-orders human children the same as do standard IQ tests. Thus,the g factor of IQ tests reflects the same kind of ability to dealwith complexity that is measured by the animals [sic] testswhich most clearly reveal phylogenetic differences in beha-vioural adaptive capacity.7
The immediate difficulty here is that Professor Jensen hasgiven only a very partial citation for the evidence on which hisassertions in this area rest: 'Many of these tests have been des-cribed by Viaud, i960'. Viaud gives no details of any test applied
6 Ibid., p. 118. 7 Ibid., p. 120.
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to fish, no details of any single test that has been applied tomore than three of the seven species Professor Jensen mentions,and, most seriously, makes no reference whatsoever to any corre-lation between any test applied to both humans and animals anda standard IQ test. Viaud says only that
In 1935 Gottschaldt studied a group of one hundred hospital-ized children between the ages of two and ten. He dividedthem into four groups in descending order of intelligence;normal, feeble-minded, imbecilic, and idiotic, and set all ofthem the same, or nearly the same, problems Kohler had sethis chimpanzees. The results were comparable, and so was theorder of difficulty which emerged . . .8
It has been commented before9 that when dealing with ProfessorJensen's citations it is a good idea to go back to the originals andcheck what they actually say (helpful, even, to track down theraw data—cf. Burt)10. The wisdom of such a course is shownhere. "Exactly the same' is not exactly the same tiling as 'com-parable*. More importantly, a careless reader might have comeaway from Professor Jensen's phrasing with the impression thatViaud's account dealt in some way with standard intelligencetests—that the children and the primates mentioned in the linebefore the citation were the same children and the same primatesmentioned in the line after. A division by undescribed meansinto normal, feeble-minded, imbecilic and idiots is plainly nota standard IQ test, and no possible deductions can be madefrom it about g.
If one does not wish to believe that Professor Jensen has un-warrantably extended the inferences that can be made from thedata he cites, one must assume that he rests his case on otherdata he has omitted to cite. This is unfortunate, because hisargument does hinge on the point. It is not contested, after all,that there are differences in the mode of mental functioningbetween animal species, or that a dog is able to perform a widerrange of operations than a fish but fewer than a person. What is atissue is whether the governing factor in every case is the posses-sion of a greater or lesser amount of the same quality, and
8 G. Viaud, Intelligence; its Evolution and Forms (London, Hutchin-son, 1960), p. 44.
9 See, for example, L. Hudson, The Cult of the Fact (New York, HarperTorch, 1973), pp. 115-20; and L. Kamin, The Science and Politics of IQ(Penguin, 1977). pp. 178-207.
10 D. D. Dorfman, 'The Cyril Burt Question; New Findings', Science,vol. 201, no. 4362, 29 September 1978.
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whether, if this is so, this quality is the same quality that ismeasured by IQ tests. Some bridge needs to be established be-tween IQ tests and animals; and that we are not given.
Should we accept that other tests similar to those describedby Viaud, but involving a linkage with IQ, have been carriedout and have produced data to support Professor Jensen's con-clusions, it is still necessary to draw attention to the methodo-logical problems involved in grading animals against humans.Some are physical; Viaud's observation that 'Dogs and catsgenerally have little difficulty in solving roundabout problems,but fail when faced with prehension problems, i.e. they cannothaul in the goal object by pulling a string'11 is capable of a num-ber of interpretations. We may have disposed of culture biasonly to be faced with species bias. It may be that it is possible toovercome this, but the point needs to be demonstrated. Otherproblems have to do with the mode of analysis. The area such testscover—the area of pronounced mental retardation and below—isan area in which all standard IQ tests are admittedly least ac-curate, having been standardized virtually invariably on popula-tions that did not include the retarded. Even if Gottschaldt hadgiven his hospital children a recognized IQ test the results wouldcontain a high degree of inaccuracy. Looking at it from the otherdirection it is, as Professor Eysenck comments, very difficult to ex-tract evidence of g from a restricted population of the Verybright, or rather dull"12 and for purposes of IQ testing all animalsare definitely in the latter group. A still more general difficultyis that we are comparing a factor that differentiates between in-dividual humans to a factor that differentiates between species;we are not matching like with like. What is the within-speciesvariance on these tests? Are the IQs of hens normally distributed?The point has some bearing on whether what we call 'intelli-gence' in humans displays any of the same characteristics as 'in-telligence' in animals. Does intelligence correlate with place inthe pecking order?
It is here that the argument falls back, as psychometric theoryinevitably does, on an appeal to common sense. Professor Jensensays that There is virtually universal assent that some animals aremore intelligent than others. By what criteria do we judge thedog to be more intelligent than the chicken, the monkey moreintelligent than the dog, and the chimpanzee more intelligent
11 Viaud, op. cit., p. 29.12 H. J. Eysenck, The Inequality of Man (London, Fontana, 1975), p. 51.
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than the monkey? Zoologists, ethologists, and comparative psy-chologists have amassed a good deal of information regardingthis question.'13 They have done nothing of the sort. What heappears to mean is not. that these groups have collected informa-tion on the criteria we use to rank animals—that is a function ofour psychology or social structure (what are the relative placesof the horse and the dog in England and Arabia?); they havecollected differences between animal groups that correlate withour rankings and can be used to validate and refine them. It isexactly this transition from 'intelligence' as a piece of commonsense, what everybody knows, to 'intelligence' as a product ofintelligence tests that is objectionable. Professor Jensen is sayingthat when we attribute intelligence to animals we are referring tothe same thing that is being measured by zoologists, and thecoincidence proves that both exist A similar use of commonassent occurs in the argument that because most people say thatlawyers are more intelligent than dustmen, and because lawyersscore higher on average than dustmen on IQ tests, this shows thatIQ tests measure intelligence; the correlation is taken as valida-tion both of the tests and the social scale. An alternative hypothe-sis would be that the tests and the general belief correlate be-cause both spring from a common process whereby a societyevolves and establishes stabilizing structures of thought. Whether,however, lawyers score higher because their work requires morebrains or because the test measures class values* the end resultis in accordance with 'common sense' and those who contest itare seen to be denying what everybody knows—that there is ahierarchy, that some people are rich in intelligence, some poor,and most in between. It is this wholesale assumption of 'commonsense' in psychometrics that represents its main strength and atthe same time most undermines its claims to be treated as ascience.
Brief note must be taken of the 'further evidence of the bio-logical basis of intelligence'14 that Professor Jensen mentions. Thequestions of the heritability of IQ and the correlations betweenthe IQs of close relations have been discussed at length else-where, and I shall not go into them here. He also mentions,however, correlations between g and
anatomical and electrophysiological brain measurements. The13 Jensen, 'The Nature of Intelligence and its Relation to Learning', p.
118.14 Ibid., p. 120.
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relationship between brain size and IQ has been greatly playeddown in most recent psychology textbooks. But a thorough andmethodologically sophisticated recent review of all the evid-ence relevant to human brain size and intelligence concludesthat the best estimate of the within-sex correlations betweenbrain size and IO is about +0-30, taking proper account ofphysical stature, birthweight, and other correlated variables(Van Valen, 1974) ,15
Here, again, Professor Jensen's use of his sources stretches thebounds of academic civility. Van Valen's paper is on the relationof brain size and intelligence—which he nowhere defines—notIQ; only four out of the eight surveys he considers relevant usedIQ tests. It is in fact a mark against Van Valen that he consideredthe earlier data usable. Pearson's researches in 1906—the Stan-ford-Binet test was first standardized in 1913—are surely in psy-chometric terms rudimentary fumblings and in general suspectbecause of the researcher's known prejudices ('in a painstakingstatistical study of the inferiority of Jewish immigrants, he con-cluded that while their average mental ability was somewhatlower than that of native-born Englishmen, the clearest differencewas that Jewish children were innately dirtier than Gentileones*.).16 One of the besetting sins of psychometrics is that itcontinues to hoard its references long after they have gonethoroughly rotten, as if the transformation into number raisedthe experiments into a sphere where their methodology couldnot date. (It is a minor foible of Professor Jensen's to extendthe shelf life of his references by using secondary citations. It ismore acceptable to cite *a recent review' than Pearson; and wouldhis comparison between retarded children and chimpanzeessound as convincing if it was made clear that the experimentstook place in the Germany of 1935?).
The data Van Valen uses, whatever its flaws, record an ob-served correlation between head size and intelligence of o-i.The methodological sophistication admired by Professor Jensenconsists in the methods Van Valen uses to raise this figure to 0 3 .
The observed correlation of 0 1 is between poor measures ofintelligence and poor measures of brain size. Any real relation-ship between intelligence and brain size will be diluted bythe random noise introduced by inadequate measurement. Thisloss of information can be qualified. Let i denote intelligence,1 5 Ibid., pp. 120-1.1 6 J. M. Blum, Pseudoscience and Mental Ability (New York, Monthly
Review Press, 1978), p. 50.
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b brain size, and c external cranial size. Assume that c is corre-lated with i only through its relationship with b. Then . . .pic = pibpbc. For example, we can take pic = o-i and pbc= 05 .Then pib = 0-2 . . . We can apply the same equation to loss ofinformation because of poor measures of intelligence. If theloss here (1 ~p2) is 05 , pib rises to about 0-3."
Professor E. J. Williams of the Statistics Department of Mel-bourne University comments that:
The recorded correlations, even when statistically significant,are small in magnitude, suggesting that about one per centof the variability in intelligence is associated with head size.Van Valen's attempt to establish that the 'real' association ishigher than that observed is invalid, since it does not reallytake account of the sampling errors in the estimates of theother correlations (although it refers to them).18
It might also be noted that the attempt relies on assuming exactlywhat Van Valen is being required to prove—namely, that in-telligence correlates with brain size. When we take into considera-tion that he has also given no grounds for his assumed correla-tion of 0 7 between intelligence tests and intelligence, it is dif-ficult not to conclude that the most recent psychology textbookswere quite right. Professor Jensen's later citation of 'such alreadywell established facts, for example, as the correlation (of about= 30) between brain size and IQ (Van Valen, 1974J*19 exem-plifies his belief that propositions extracted none too scrupulouslyfrom flimsy data may be firmly established by constant repetition.
I do not, of course, expect the undermining of Professor Jen-sen's assertions in this particular area to have any effect on hisgeneral credibility. His position in the modern pantheon as theman of science reluctantly driven to state unpleasant truths isnot based on his performance in debates of this sort and will notbe affected. The discussion will not make progress until it is re-cognized that psychometrics represents a numerical embodimentof one view of the proper construction of society.
17 L. Van Valen, 'Brain Size and Intelligence in Man', American Journalof Physical Anthropology, vol. 40, p. 418.
18 In a letter to the author, 28 March 1979.1 9 Jensen, 'The Current Status of the IQ Controversy', p . 11.
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