The historical sections of Jensen's (1998, 1999) "The g Factor" do not mention the strong connections between the origins of intelligence testing and eugenics. They also fail to acknowledge some of Jensen's major critics, and certain changes in his own views as expressed over the past 30 years. This failure to deal with his critics and with the troubling history of aspects of intelligence testing may make it difficult for Jensen to convince an audience not already converted to his views.
2. Jensen portrays Galton quite unequivocally as a hero, characterized by "what Hollywood calls 'star quality,'" along with a variety of "charming eccentricities" (p. 7). Although he acknowledges that Galton wrote unflatteringly about the "comparative worth" of non-European ethnic groups, Jensen excuses this style of writing as "common among nineteenth-century intellectuals, without the slightest implication that they were mean-spirited, unkindly, or at all unfriendly toward people of another race" (p. 15). I would suggest that this lets Galton off too easily. His published accounts of African native groups (e.g., Galton, 1889) were rife with decidedly "unfriendly" characterizations, likening natives to baboons, pigs and dogs; and some of the suggestions in The Art of Travel on the "Management of Savages" (Galton, 1872, pp. 308-310) hardly betray "kindly" sentiments. Elsewhere I have shown that although some of Galton's contemporary explorers and ethnographers (e.g., Richard Burton and Robert Knox) were similar to Galton in their outspoken racism, others including David Livingstone and John Hanning Speke were considerably more moderate (Fancher, 1983). Galton's cousin Charles Darwin was also notably less harsh in his racial attitudes. In general then, while some Victorians expressed crude racial views similar to Galton's, others did not.
3. In one sense these are minor issues with little direct bearing on the larger content of Jensen's book. In another sense, however, they seem reflective of a general disinclination to acknowledge the more disturbing aspects of the social history of the intelligence testing movement. It is true that Galton himself generally promoted positive as opposed to negative eugenics: i.e., the encouragement of breeding by the able, rather than its prevention by the "unfit." He died before negative eugenics became a popular movement, leading to the involuntary sterilization of thousands of people diagnosed as mentally deficient in the U.S. and Canada. Galton cannot be held personally responsible for those practices, much less for the atrocities perpetrated in the name of "race hygiene" in Nazi Germany. But still there were indubitable historical links between his writings and these later enormities (Weindling, 1989), and it is precisely because of this disturbing history that so many people are nervous about hereditarian theories of intelligence. To ignore or to sugarcoat this history seems naive at best.
4. Jensen's coverage of more recent history is also spotty. He never even mentions the names of Stephen Jay Gould (1981) and Leon Kamin (1974), two of his most visible opponents in the IQ controversy. Neither does he explicitly acknowledge some changes in his own own views over the years, which may have been partly inspired by his critics. In 1969, for example, Jensen declared that "the best single overall estimate of the heritability of measured intelligence" was .81; in 1980 this estimate fell to "probably near .75," and in 1981 (p. 103) to "a central tendency around .70" (Jensen, 1969, 1980, 1981; pp. 51, 244, 103). The present book states, "the broad heritability of IQ is about .40 to .50 when measured in children, about .60 to .70 in adolescents and young adults, and approaches .80 in later maturity" (p. 169). Clearly, Jensen's heritability estimates have been drifting lower and becoming more nuanced over the years.
5. Jensen's highest estimate, in 1969, rested heavily on the work of Cyril Burt, which he authoritatively declared to be "a 'must' for students of individual differences" (1969, p. 33). In the present book he deals with the intervening "Burt Scandal" only briefly and allusively in a single footnote (pp. 198-199). Somewhat disingenuously, he cites only himself as having "brought into question" the accuracy and authenticity of Burt's reported findings on separated identical twins. Completely overlooked is Kamin's crucial role in discrediting the Burt results, a role that is well known to all who followed the scandal closely. Jensen's footnote also attempts to minimize the effect of excluding Burt's data from current analyses, on the grounds that Burt's results "are so closely in line with those of other studies" that their inclusion "would make little difference." Jensen neglects to mention that the feature that had made Burt's study seem so important to him in 1969 was not the magnitude of the reported IQ correlation, but rather the claim for completely random placement of his twins in a full socioeconomic range of foster homes. Kamin's (1974) analysis not only demolished Burt's credibility, but also showed that no other separated twin study published to that date could come close to claiming random placement.
6. The results of the more recent and highly touted "Minnesota study" of separated twins have not yet been published in great detail, but it seems unlikely that they will support such a claim either. The Minnesota investigators have summarized their findings as indicating, "In the current environments of the broad middle class, in industrialized societies, two-thirds of the observed variance in IQ can be traced to genetic variation." They explicitly advise that their results "should not be extrapolated to the extremes of environmental disadvantage still encountered in society" (Bouchard et al., 1990, p. 227). Here is a heritability estimate substantially lower than Burt's .81, and explicitly restricted to the middle class of the population. (The effect of the restriction, of course, is to inflate the heritability estimate.) Jensen's statement that the loss of the Burt study makes "little difference" to the hereditarian case is highly questionable.
7. Given Jensen's own rough and sometimes inappropriate treatment at the hands of his less temperate critics, he may understandably feel at times as if he is engaged in a war. His neglect of his critics and of the less savory aspects of the history of intelligence testing may be the result of a "take no prisoners" mentality. But however understandable such a response might be, its main effect is counterproductive. It would be far better to adopt an attitude similar to that expressed by E. O Wilson when he described himself as having been "blessed with brilliant enemies" whose critiques "redoubled my energies and drove me in new directions" (Wilson, 1994, p. 218). Until Jensen explicitly and respectfully addresses the arguments of his numerous responsible opponents, and acknowledges the socially fraught history of intelligence testing and the fact that even the most authoritative-seeming knowledge of one generation is provisional and liable to being superseded in the next, he will be preaching primarily to the converted. And that is too bad, because he is an accomplished scholar with much to say that deserves wide and serious debate.
Bouchard, T. J, Lykken, D. T., McGue, M., Segal, N. L. & Tellegen, A. (1990). Sources of human psychological differences: The Minnesota study of twins reared apart. Science, 250, 223-228.
Fancher, R. E. (1983). Francis Galton's African ethnography and its role in the development of his psychology. British Journal for the History of Science, 16, 67-79.
Galton, F. (1872). The art of travel, 5th edition. London: Murray.
Galton, F. (1889). Narrative of an explorer in tropical South Africa. London: Ward, Lock and Company.
Gould, S.J., (1981). The Mismeasure of Man. Penguin, London.
Jensen, A. R. (1969). How much can we boost IQ and scholastic achievement? In Environment, heredity and intelligence, compiled from the Harvard Educational Review (pp. 1-123). Cambridge, MA: Harvard Educational Review.
Jensen, A. R. (1980). Bias in mental testing. New York: Free Press.
Jensen, A. R. (1981). Straight talk about mental testing. New York: Free Press.
Jensen, A. (1998). The g Factor: The Science of Mental Ability. Praeger
Jensen, A. (1999). Precis of: "The g Factor: The Science of Mental Ability" PSYCOLOQUY 10 (23). ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/1999.volume.10/ psyc.99.10.023.intelligence-g-factor.1.jensen http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?10.023
Kamin, L. (1974). The science and politics of IQ. Potomac MD: Erlbaum.
Weindling, P. (1989). Health, race and German politics between national unification and Nazism, 1870-1945. Cambridge: Cambridge University Press.
Wilson, E. O. (1994). Naturalist. Washington, DC: Island Press.