EuwwsntEamm=nts

HighImpact S&nce and the Case of Arthur Jensen o Number 41 October 9, 1978

Great science, whose importance times; 1976, 66 times and 1977, 61 is recognized, always has high im- times. Many of these citations, 101 pact. But not all high impact science to be exact, appeared in letters, is great science. notes and editorials in journals. The No other statement about citation rest, 537, were references in arti- analysis needs as much repetition. cles. We are unable to report in how However, only on rare occasions many books it was cited. can we identify specific examples of Since Jensen’s article was cited high impact papers that have a large so often it proved to be one of the percentage of critical or negative ci- papers on our list of 100 most-cited tations. The reason for this is sim- SSCl articles. z Consequently we ple. Scientists generally disregard wrote to Jensen asking him to write the obviously erroneous or the triv- a commentary on his article for Ci- iaI. Yet in the case of Arthur Jen- ~ation Classics. We are publishing sen’s 123-page work, “How much that commentary in this issue. can we boost IQ and scholastic As I promised in the essay ac- achievement?” 1 they did not disre- companying the SSC1 100 most- gard it. Perhaps scientists felt they cited articles list, we have con- could not disregard it. ducted an investigation into why the To appreciate the impact of Jen- Jensen article was so frequent~y cited. sen’s article in the 1969 Harvard Later in this editorial I will pre- Education/ Review one onfy has to sent the results of that investigation. look at the large number of citations Arthur Jensen was born August it has received. The Science Cita- 24, 1923 in , Califomia.3 tion Index@ (SCl@) and the So- He has a BA in psychology from the cial Sciences Citation Index TM University of , Berkeley (SSCITM) indicate it was cited 638 (1945); MA in psychology from San times between 1969 and 1977. The Diego State College (1952) and a data for each year are as follows: Ph. D. from Teachers College of 1%9, 20 times; 1970,62 times; 1971, (1956). Jen- 103 times; 1972, 74 times; 1973, 110 sen’s dissertation was entitled “ Ag- times; 1974, 67 times; 1975, 75 gression in fantasy and overt

652 behavior. ” After graduation, Jen- forts to produce lasting sen worked for a time with Hans changes in the IQs of disad- Eysenck, whose views on genetic vantaged children meant that determination of were the programs should be expressed in his 1971 book The lQ reevaluated. argumenf.4 His views seem to 2. Questioned the prevailing idea closely parallel Jensen’s. 5 At the that IQ differences are the re- time he wrote his controversial arti- sult of environmental factors. cle, Jensen was a member of the 3. Discussed the nature of intel- faculty of the University of Califor- ligence and gave a of nia at Berkeley and of the Institute IQ testing. of , where he still works. 4. Correlated occupation with According to Stanford University intelligence. education professor Lee Cronbach, 5. Using evidence presented by Jensen’s article was prepared in rel- Sir , showed how ative haste.8 In his preface to IQ can be viewed as nearly and education 7 Jensen normally distributed through- himself notes that the article grew out a population. He then pro- out of two lectures he gave. One vided a variance model to was on “Social class, race, and explain how IQ could be genetics: implications for educa- broken into its genetic and tion” and dealt with the question of environmental components. educating children of differing learn- 6. Discussed — a ing abilities. The other, on intelli- statistical tool used to assess gence testing, presented Jensen’s the degree to which differ- findings on the interaction among ences in intelligence within a social class, intelligence, and rote population are due to genetic learning ability. The graduate stu- factors. Backed by kinship dent editors of the Harvard Edu- studies by Burt and others, cational Review asked Jensen to Jensen proposed that there is synthesize the lectures into one a .8 heritability factor. This statement of views conforming to an means that 80% of the var- outline they presented. He did so. iance of intelligence in the Cronbach points out that Jensen let observed population can be other work crowd his schedule’ ‘un- attributed to genetic factors. tilmid-September and then put to- 7. Said that some environmental gether 50,000 words in two factors such as prenatal care months. ”e can influence intelligence. The Jensen articlel covers a lot of However, he asserted that so- territory. Some of its main points cial class and racial variations are listed below. In the article Jensen: in intelligence (such as the one 1. Argued that the failure of standard deviation, 15 point compensatory education ef- IQ difference between groups

653 of blacks and groups of paper were also gathered together m whites) cannot be accounted book form. 9 for by environmental factors. To examine the nature of the Jen- 8. Argued that a deprived envi- sen controversy we decided to do an ronment can keep a child from in-depth citation study at IS I@. performing up to his genetic Using both the SSCI and the SCl potential, but that an enriched we randomly selected 60 articles, educational program cannot (every 9th article) or about 10% push the child above that po- of the items that cited the 1%9 Jen- tential. sen work, to see why the authors 9. Presented his own theory that did so. people are endowed with two Of the 60 papers in our sample, 29 kinds of learning ability, as- cited Jensen’s article negatively. sociative or Level I and cogni- This number includes articles that tive or Level II. According to took exception to almost every Jensen, disadvantaged chil- point presented in the paper. It also dren do better on Level I tasks includes those in which the authors and not as well as advantaged debated specific points Jensen children on Level 11 tasks. made. Eight of the articles cited Level I tasks include rote Jensen’s paper as an example of a learning and selective trial and controversy. Eight more used the error learning with feedback article as a background reference. for correct responses. Level II Only fifteen of the articles cited tasks include concept learning Jensen in agreement with his posi- and problem solving. He con- tions, and seven of them only on cluded that education should minor points. Further readings have be changed. ‘LDiversit y rather contkmed that our sample is typi- than uniformity of approaches cal of the way authors have cited would seem to be the key to the Jensen work. making education rewarding Fourteen of the 60 papers cited for children with different pat- Jensen’s article as part of the con- terns of abilit y.” tinuing “gene vs. environment” From a quick reading of the controversy. This familiar argu- above highlights it is easy to see that ment, sometimes known as the many of Jensen’s conclusions were nature/nurture debate, pits those likely to provoke controversy. So who believe in environmental de- sure of this were the editors of flar- termination of IQ or other traits vard Edtdcarional Review that they against those who believe that these “arranged for a panel to provide traits are genetically determined. Of comments” on the work, Cronbach the 14 papers, five were clearly said. s Those comments were later against Jensen’s stand that genetic published in book forms Sub- factors, more than environmental sequent comments on the Jensen factors, account for differences in

654 IQ between individuals and be- ences and the correlations between tween racial and cultural groups. any two sets of measures are com- Four of the papers supported his pletel y independent of one another. stand. Five more used Jensen’s ar- There is no statistical basis “for ticle as an example of a study em- predicting one on the basis of broiled in the controversy. knowledge of the other,” as Jensen Eleven of the articles we selected seems to do in his article. called into question Jensen’s use of Eight of the papers in the sample data. None of them specifically specifically mentioned Jensen’s use supported his methodology. One of of IQ measurements. Six of the the articles attacking Jensen’s use of eight expressed opposition to the data was by David Layzer of the way the measurements were used. Harvard College Observatory.’0 In M. W. Feldman and biologist R. C. the article, called “Science or Lewontin, for example, discussed superstition (a physical scientist Jensen’s use of a variance model to looks at the IQ controversy ),” measure IQ populations in “The Layzer “analyzes the implicit as- heritability y hang-up.”’2 The sumptions underlying Jensen’s analysis of variance cannot really theoretical analysis and demon- “separate variation that is a result strates that they are untenable. ” He of environmental fluctuation from points out that the IQ measure- variation that is a result of genetic ments do not satisfy certain formal segregation, ” the authors said. The requirements needed to make them two articles not negatively citing reliable and meaningful. Thus, ac- this aspect of Jensen’s work refer- cording to Layzer, the estimates of enced the article as part of the de- heritability given by Jensen are bate over using IQ measurements. meaningless. He also says that the Eleven of the articles referred to data Jensen provides do not support Jensen’s correlation between race his view that children with low IQs and genetic inferiority. Nine of or children of parents with low IQs these attacked Jensen’s conclu- have limited capacity for acquiring sions, one agreed with them and one cognitive skills. cited Jensen’s work as an example Another of these articles on Jen- of an idea involved in the con- sen’s use of data, this one by M. troversy. A typical article in this Golden and W. Bridger, 11 “A refu- group was Richard Wienke’s on tation of Jensen’s position on inteUi- racial differences in educability gence, race, social class and hered- which presents evidence’ ‘that black ity, ” attacked his use of statistics. students learn as weU as white. ” 13 The researchers flatly said, “Jen- Seven of the papers on the list sen’s fundamental error lies in his referenced Jensen’s remarks on the misuse of statistics to make unwar- failure of compensatory education. ranted statistical or logical infer- Three of them agreed that these ences from one set of data or facts programs had failed and four did to another set of facts.” Golden and not agree. One paper that agreed Bridger note that mean IQ differ- with Jensen’s views was” Compensa- tory education and contemporary ject, closely examined Jensen’s liberalism in the : sources to see if their work really sociological view” by D. C. Morton backed his conclusions. 16 Although and D. R. Watson. The authors he found many instances where Jen- cited Jensen to counter the liberal sen seemingly misused the data that argument that working-class groups others reported, he also found some are in need of “compensation” at startling inconsistencies in the work school. *4 On the other hand, Martin of one of Jensen’s primary sources. Deutsch presented data to support To back much of his line of his argument that Jensen ‘‘prema- reasoning, Jensen relied on the data turely classified compensatory edu- assembled by Sir Cyril Burt, the late cation as a failure.”] 5 In the article British psychologist. Burt’s kinship “Happenings on the way back to studies had been looked upon as the forum: social science, IQ and standards for the scholarly commu- race differences revisited, ” nit y, Jensen particularly leaned on Deutsch concluded that ‘‘continu- Burt’s studies of separated identical ous and carefully planned interven- twins to draw his conclusions. Ac- tion procedures” could have a posi- cording to Kamin, with support tive influence on the performance of from others who have now closely disadvantaged children. examined Burt’s data, the numbers The remainder of the papers in Burt supplied are unusable. our sample cited Jensen for reasons For three of the twin studies, ranging from disagreement with his which included 21 pairs, “over” 30 definition of intelligence to observa- pairs and 53 pairs of twins respec- tions about the lack of new data pre- tively, the correlation between the sented in the work. The authors IQ scores of the separated twins, claimed that Jensen just rearranged given by Burt, was .771. This corre- existing data from studies done by lation remained the same through others, relying on the previous data three studies of unequal size. Not as accurate. only did that particular correlation We end our citation study here. remain constant over the different But in order to further understand sample sizes but the IQ correlations the impact of the Jensen paper we between identical twins reared to- did some additional research. We gether also stayed the same over found that Jensen’s reliance on the three sample sizes. original work of others to make his Kamin also charged that Burt’s case has brought much vocal criti- papers “are often remarkably lack- cism from educators, psychologists, ing in precise descriptions of the scientists and others. Probably the procedures and methods that he most outspoken of the experts who employ ed. ”]G Items such as the attacked Jensen’s use of data de- children’s ages, sexes, name of the veloped by others is psychologist test administered and how and when Leon Kamin of Princeton Univer- the tests were given are often miss- sity. Kamin, who wrote a book and ing from the data supplied in the has delivered lectures on the sub- published version. When these find-

656 ings began to cast some doubt on dard’s assessment that ‘’83 percent Burt’s work, others began to inves- of Jewish immigrants were feeble- tigate. Out of these investigations minded. ” Yet many are willing to came further charges, well-reported agree with Jensen when he states in the science press,l 7 that Burt may that “on the average, Negroes test even have “invented” the data and about 1 standard deviation (15 IQ “made-up” the co-workers he said points) below the average of the collaborated with him on some of white population” and draws his his studies. conclusions as to what this test Some researchers have pointed score means. out that the discrediting of Burt’s In the chapter “IQ, heritability data does not remove the “under- and inequality,” in The IQ con- pinnings of the view that intelli- troversy, N. J. Block and Gerald gence has a large genetic compo- Dworkin attack, among other as- nent. ”18 According to Bernard pects of the Jensen article, the cor- Rimland of the Naval Electronics relations he drew between IQ and Laboratory and Harry Munsinger of job categories. According to the re- the Department of Psychology of searchers, “Even if the number of the University of California at San hairs in a person’s nose correlated Diego, “Such a conclusion is un- with success in the same way IQ warranted. ” In a letter to Science, does, no one would be entitled to the two researchers presented a conclude that a certain level of nose chart of correlation coetllcients for hair numerosity is a requirement or “intelligence” test scores from 52 a condition of eligibility for any level studies. They asserted that “the de- of success” (p. 414).5 letion of Burt’s data would have no Of course, not all those who appreciable effect on the overall pic- found fault with the Jensen article ture. ” The data “demonstrating the were as vehement as those men- heavy dependence of IQ on genetic tioned above. The early reaction of factors are far too solid to be shaken Lee Cronbach, for example, in his by the rejection of the work of any 1969 paper “ Heredity, environ- single investigator — even Sir Cyril ment and educational polic y‘’ was Burt.’”8 to disagree with several aspects of The validity of the IQ test itself to the Jensen article.8 Nevertheless he give accurate measures of the said, “Professor Jensen is among capabilities of a group of people has the most capable of today’s educa- been questioned by many critics. tional psychologists. His research is Kamin in The science and politics energetic and imaginative. ” Cron- of IQ 16 pointed out that IQ tests bach called the Jensen paper “an administered in the early part of this impressive example of [Jensen’s] century “proved” the inferiority of thoroughness. ” He added, “ Dr. certain immigrants to the US. No Jensen has girded himself for a holy reputable scientist today would, for war against ‘environmentalists’ and example, agree with Henry God- his zeal leads him into over-

657 statements and misstate merits.” llshed. He dld so “as part ot” hm Cronbach went on to say, “Because continuing campaign to have the learning abilities are plural, they are Academy study the effects of inter- not adequately conceptualized by racial mating” (p. 78).5 Shockley Jensen’s Level I-Level 11 sys- also wrote several papers defending terns. ” He also disagreed with the Jensen article. In his 1971 article Jensen on the implications of his “Models, mathematics and the findings for educational policy. moral obligation to diagnose the or- In a subsequent article that ap- igin of Negro IQ deficits” Shockley peared in A mericon Psychologist in concluded that “nature has coior– 1975, Cronbach analyzed the con- coded groups of individuals so that troversies over mental testing that statistically reliable predictions of have developed in the last five their adaptability to intellectually decades. He noted, ‘4Our scholars rewarding and effective lives can chose to play advocate when they easily be made, . . . If those mem- went before the public, and they bers of our black minority with the abandoned scholarly consistency least percentage of Caucasian genes . . . .The academic needs writing are both the most prolific and the skills of an entirely unaccustomed least intelligent, then a form of order if he is to make sure that no genetic enslavement is the destiny unwanted implication will be drawn of their next generation. ”z” from a buried sentence . . .“6 Many of Jensen’s supporters say Jensen had his unabashed sup- that those who oppose them seek to porters within the scientific com- restrict free scientific inquiry. The munity. For example, Harvard result, according to Edward O. Wil- psychologist Richard Hermstein in son in his article “The attempt to his 1971 A flantic article argued that suppress human behavioral genet- American is heading for a ics, ” has been that “studies on the meritocracy based on heredity and genetics of cognitive abilities includ- IQ differences. 19 According to ing intelligence have been inhib- Hermstein, society in the future will ited. ”z’ While many scientists be socially stratified by inborn dif- would support Wilson’s call to de- ferences. Social standing will be politicize science, some will point given to groups with higher IQs. out that science does not exist in a Herrnstein’s arguments have been vacuum, Sensitive subjects can be called the popularization of Jensen. approached, but the data at least Nobel laureate physicist William should be accurate. the methodology Shockley shared Jensen’s views as sound and the conclusions logical. well. According to Lewontin,5 in During the nine years since the “ ” reprinted publication of his article, Jensen has in The IQ contrm’ersy, Shockley replied repeatedly to his critics in distributed Jensen’s paper to every letters and articles .22’33 The first member of the National Academy major work in response was ‘‘ Re- of Sciences soon after it was pub- ducing the heredity-environment

658 uncertain y” which appeared along- the most controversial . . .‘” in- side several critical articles in the cluded in Genetics and education book Environment, heredity and was a reprint of the 1%9 article. The intelligence. In this article, Jensen second book, Educational differ- noted that many of his critics agreed ences (1973) was a collection of arti- with his major stands but disagreed cles dealing with “the psychology of with him on minor points. He added, mental abilities.’ ’35 Topics such as “If there are weaknesses in the the heritability of intelligence, indi- methods and evidence I have pre- vidual differences in learning and sented, and of course there inevita- -fair testing were covered in bly are at this stage, we would do the book. Educability and group well to note them as a basis for seek- differences, also published in 1973, ing more refined research methods dealt “with the fact that various and more and better data, rather than subpopulations (social and ethnic as a basis for minimizing the . . . groups) . . . show marked differ- importance of these questions. ” 8 ences in the distributions of those In some of his responding works. mental abilities most importantly Jensen retited his critics point by related to educability and its occu- point, prompting counter responses. pational and socioeconomic cor- For example, after Layzer wrote his relates.’ ‘3s All three of the works critical article, 10Jensen replied with supported the 1%9 article. a 26-page detailed work30 that ex- Jensen has continued to perform plains why IQ scores can be viewed work in the field of genetics and as fitting an interval scale and why education. Since 1969 he has pub- the concept of heritability could be lished well over twenty articles that used to understand human differ- expanded on or claritled the points ences, among other things. Layzer, made in the 1969 article or repre- in turn, counterattacked with a 19- sented new research in this field. page article entitled “Jensen’s re- His recent studies have led him to ply: the sounds of siIence,” in which perform a cautious about-face on he accused Jensen of serious omis- his stand that IQ is primarily geneti- sions and irrelevancies. 34 This type cally determined .37 of exchange was carried on several In his 1977 article “Cumulative times with others, as the debate con- deficit in IQ of blacks in the mral tinued and remained unresolved. south” Jensen studied 1,479 chil- After the publication of his 1969 dren in a very poor area of Georgia. article, Jensen wrote three books. He compared IQ test scores of pairs Genetics and education (1972) was of black siblings and white siblings his first. In his preface he called this to test the hypothesis that environ- work a “book-length treatment of mental factors cause IQ scores to those parts of my HER article decline. The black children showed which were generally regarded as a decline in IQ scores between the

659 ages of 5 and 18 while the white According to the article, “the cor- children did not. He compared re- nerstone of his latest work involves sults with those from another study reaction time (RT), as measured on of more affluent blacks in California a rather simplistic panel consisting which he also conducted, and con- of sets of. . . lights. RT is measured cluded that the Georgia study by how long it takes a person to lift “would seem to favor an environ- his finger off a central pushbutton mental interpretation of the pro- and move it to the button under the gressive decrement phenomenon light that has just flashed on . . .‘’ .,. . It appears that a cumulative Jensen’ ‘found that reaction times of deficit due to poor environment has the more than 400 subjects corre- contributed, at least in part, to the lated ‘across the board’ with their relatively low IQ in the present performances on a variety of verbal sample.’ ’37 and non–verbal intelligence mea- Jensen’s recent work on the IQ sures. . . . Although he found no sex controversy appeared in the March differences in performance, Jensen 1978 Australian Psychologist. 38 In says he did detect ‘black-white dif- it, he reviewed the current status of ference at the junior college level,’ the debate, analyzing several gen- with blacks exhibiting somewhat eral areas still under discussion by slower reaction times. . . .“ scientists. These include the nature According to the Science News ar- and measurement of intelligence; ticle, Jensen emphasizes “that these the heritability of IQ within cultur- results do ‘not at all’ alter his previ- ally homogeneous populations; the ous conclusions that environment genetic components in IQ differ- contributes to intelligence at some ences between groups and the social level. ‘I’m not putting any stress on and educational implications of a the racial aspects,’ he says of his genetic component in IQ variance. latest research. ‘That would be kind The article attempts to place the of a red herring and detract from the controversy in perspective some use of reaction time’ as an indicator nine years after the publication of of intelligence. ” the Harvard Educational Review Usually when a researcher pre- piece. sents mediocre or inferior work to Jensen’s role in the IQ con- the scholarly community that work troversy continues even as this elicits no response. But when an ar- essay goes to press. An article in the ticle is published in a highly visible September 9 issue of Science News and reputable journal such as the reported a study presented by Jen- Harvard Educational Review, as sen at the recent American Psy- was Jensen’s article, even if it didn’t chological Association meeting in have methodological problems, it Toronto that indicated that IQ “has was inevitable that it would not be a definite ‘biological basis.’ “3s ignored, Furthermore, scientists of

660 reputation felt compelled to rebut scientists must classify it as impor- the article after popular versions of tant but questionable science. Since it appeared in the lay press. After most high impact science proves to all, how many lay people, who be great science, the Jensen case is would be making the decisions re- an exception that illustrates one garding education in this country, must be cautious in using citation would wade through the 123-page data. But clearly it is the extreme of study? And if they did, how many science. The citation data and the would recognize the problems with realities on which they are based the research if not pointed out by show that Jensen’s work is a miles- scientists? Very few, I’m afraid. tone event in the history of social The Jensen article is certainly a high science. impact article. But contemporary

REFERENCES

1. Jensen A R. How much can we boost IQ and scholastic achievement? Harvard Educ. Rev. 39:1-123, 1969. 2. Gartield E. The 100 articles most cited by social scientists, 1969-1977. Current Contents (32):5- 14, 7 August 1978. 3. Current biography, 34th annual cumulation -1973. New York: H. W. Wilson Co., 1974.481 p. 4. Eysenck H. The IQ argament. Freeport, NY: Library Press, 1971. 155 p. 5. Btoek N J & Dworkin G, eds. The IQ controversy. New York: Pantheon Books, 1976.557 p. 6. Cronbaeh L J. Five decades of public controversy over mental testing. Amer. Psychol. 30:1-14, 1975. 7. Jensen A R. Genetics and education. New York: Harper& Row, 1972.378 p. 8. Harvard Educational Revtew. Environment, heredity and intelligence. Cambridge: HER, 1%9. 246 p. 9. Harvard Edueattomd Review. Science, heritability and IQ. Cambridge: HER, 1%9. 97 p. 10. Layzer D. Science or superstition. (A physical scientist looks at the IQ con- troversy). 1:265-300, 1972. 11. Golden M & Bridger W. A refutation of Jensen’s position on intelligence, race, social class, and heredity. Mental Hy.g. 53:648-53, 1%9. 12. Feldman M W & Lewontin R C. The heritability hang-up. Science 190:1163-8, 1975. 13. Wienke R. Are there racial differences in educabilityy? J. Hum. Relat. 18:1190-203, 1970.

661 REFERENCES (continued)

14. Morton D C & Watson D R. Compensatory education and contemporary liberalism in the United States: a sociological view. Int. RaI. Ed. 17:289-307, 1971. 15. Deutwh M. Happenings on the way back to the forum: so,-iaJ science, IQ, and race differences revisited. Har\’~/rd Educ. R[71). 39:523-57, 1969. 16. Kamin L. The .s(ience and pf~litics ~t IQ. New York: Wiley, 1974. 179 p. 17. Wade N. IQ and heredity: suspicion of fraud beclouds classic experiment. .S[ience 194:916-9, 1976. 18. Rimland B & Munsinger R. Letter to the editor. Science 195:248, 1977. 19. Herrnstein R. IQ. Afk/nfic 228(3):43-58, 63-4, 1971. 20. Shwkley W. Model, mathematics, and the moral obligation to diagnose the origin of Negro IQ differences. Ret. of EdM. Res. 41:369-77, 1971. 21. Wilson E O. The attempt to suppress human behavioml genetics. J. Gen. Educ. 29(4):277-87, 1978. z2, Jen~n A R. criticism or propaganda? Am. p,sych(J. 24:1040-41, 1969. 23. ______A reply to Danielian. Contemp. P.sY(IIoI. 14:682, 1969. 24. __––––. Jensen’s theory of intelligence: a reply. J. EdIIc. psYciIol. 60:427-31, 1969. 25. ______Rejoinder: promotion of dogmatism. J. .$oc’. [SSIM’S25:212-7, 1969. 26. ______Counter response. J. Sot. Issues 25:219-22, 1969. 27. ------Hebb’s confusion about heritability. Am. PsYcho/. 26:394-5, 1971. 28. ______The ethical issues. Hf{munisr 32(1):5-6, 1972. 29. ------Interpretation of heritability. Am. PSYCIKJ. 27;973-5, 1972. 30. ------The IQ controversy: a reply to Layzer. Cognition I :427-52, 1972. 31. __– ____ The differences are real. P.sYchol. ToduY 7:80-6, 1973. 32. -–-–-–. The strange case of Dr. Jensen & Mr. Hyde? Am. Ps~cho/. 29:467-8, 1974. 33. ______Heritability of IQ. Science 194:6; 8, 1976. 34. Layzer D. Jensen’s reply: the sounds of silence. Cognition 1:453-73, 1972. 35. Jensen A R. Educational d$ferences. London: Methuen & CO., &73, 462 p. 36. ------Edmubilit.v and group differences. New York: Harper & Row, 1973.407 p. 37. ______Cumulative deficit in IQ of blacks in the rural south. Develop. P.sYchol. 13:184-91, [977. 38. ------The current status of the IQ controversy. Australian PsYc1701. 13(1):7-27, March 1978. 39. Jensen: Intelligence a ‘biological rhythm’. Science Nelts 114(1 1): 181, 9 September 1978.

662