Arthur Jensen is an American educational psychologist, born August 24, 1923 and educated at the University of California, Berkeley (B.A. 1945), San Diego State College (M.A., 1952) and Columbia University (Ph.D., 1956). Jensen was a major practitioner of individual differences psychology with a special interest in intelligence and the nature versus nurture debate, and eventually argued strongly for the heritability of intelligence.
Jensen was condemned as racist in the late 1960s by a generation of academics reacting to the racist atrocities of the Second World War. In one article, Jensen argued that his claims had been misunderstood:
- ...nowhere have I "claimed" an "innate deficiency" of intelligence in blacks. My position on this question is clearly spelled out in my most recent book: "The plain fact is that at present there exists no scientifically satisfactory explanation for the differences between the IQ distributions in the black and white populations. The only genuine consensus among well-informed scientists on this topic is that the cause of the difference remains an open question" (Jensen, 1981a, p. 213).
- In Chapter 12: Population Differences in g: Causal Hypotheses, Jensen writes: "The relationship of the g factor to a number of biological variables and its relationship to the size of the white-black differences on various cognitive tests (i.e., Spearman's hypothesis) suggests that the average white-black difference in g has a biological component. Human races are viewed not as discrete, or Platonic, categories, but rather as breeding populations that, as a result of natural selection, have come to differ statistically in the relative frequencies of many polymorphic genes. The genetic distances between various populations form a continuous variable that can be measured in terms of differences in gene frequencies. Racial populations differ in many genetic characteristics, some of which, such as brain size, have behavioral and psychometric correlates, particularly g."
Gould makes three criticisms. The first is the criticism most commonly leveled against Jensen by other anthropologists and biologists: that Jensen misunderstands the concept of "heritability." Heritability measures the percentage of variation of a trait due to inheritance, within a population. Jensen, however, has used the concept of heritability to measure differences in iheritance between populations (Gould 1981: 127; 156-156).
The second criticism is relatively minor: Gould disagrees with Jensen's support of the attempts of others to calculate the IQ of dead people (such as the famous Polish astronomer and Prussian monetary theorist Copernicus) (1981: 153-154).
The third criticism is significant: Gould disagrees with Jensen's belief that IQ tests measure a real variable called "g" or "the general factor common to a large number of cognitive abilities" which can be measured along a unilinear scale. This is a claim most closely identified with Cyril Burt and Charles Spearman. According to Gould, Jensen misunderstood the research of L.L. Thurstone to ultimately support this claim; Gould however argues that Thurstone's factoral analysis of intelligence revealed "g" to be an illusion (1981: 159; 13-314).
In a 1982 review of Gould's book Jensen gives point by point rebuttals to Gould's characterizations of his work, including Gould's treatment of heritability, the "reification" of "g" and the use of Thurstone's analysis (see  or ). Gould made no further response.
See also: the discussion of race and intelligence.