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Holds up well after eight years
on May 16, 2010
Jensen's capstone book, "The g. factor," has been pretty much the final word on traditional psychometric testing. Jensen refers to it often in this conversation. None of its conclusions have been successfully challenged, and in the eight years since this book's appearance the challenges have pretty much fallen off. Jensen's own work followed a different path, culminating in the 2006 publication of "Clocking the Mind: Mental Chronometry and Individual Differences." His belief was that the abstract scale for g., which has no zero and no consistent units separating measurement levels (i.e., the difference between an IQ of 90 and 91 is not the same as the difference between 120 and 121 -- all that they represent is gradients on a bell curve distribution), had been exploited to the maximum useful extent. He was looking for hard physical measurements such as reaction time to explain the same individual differences.
The three tenants of Jensenism, that compensatory education have been tried and failed, that genetic differences are more important than cultural or socioeconomic differences in explaining individual differences in IQ, and that the difference between IQ between races probably had a genetic origin, first presented in his our Harvard educational review article in 1969, had stood the test of time.
Interviewer Frank Miele provides a wonderful service in making Jensen's work accessible to readers without the statistical and scientific background required to easily read Jensen's own work. Miele poses a number of questions that cover old ground, defining the nature of intelligence, the techniques of measuring it, and its objective reality as demonstrated through with the statisticians call reliability (it seems to always measure the same thing, across time and across populations) and validity (measured intelligence correlates highly with worldly success, and does so equally well for all populations). In this discussion I use intelligence where Jensen prefers the term g. Please read g for intelligence throughout. In any case, Miele understands the material well and presented very well formulated questions.
For all the vituperation Jensen has suffered, he rather steadfastly ducks the opportunity to even scores, purporting not to understand the motives of his many detractors. He comes across as a true gentleman, though the reality is probably that he simply wants to avoid rolling in the mud. He repeatedly challenges his critics to refute him in scientific articles, juried by their peers. Of course they cannot, and Jensen knows it. The argument is effectively over.
In the eight years since publication, science has taken its own turns. The question is no longer whether differences exist -- whether or not people want to accept the differences, they know better than to argue -- but why they exist. The human genome project has shed a great deal of useful light on this. Miele includes some of the Cavalli-Sforza's work on the genetic distances between human populations, and Jensen comments but they are very useful and totally consistent with his own work, ignoring Cavalli-Sforza's obstinant refusal to follow where his own observations would lead with regard to intelligence, obviously out of concern that being un-PC would jeopardize his continued funding at Stanford.
Cavalli-Sforza and his followers continue to find new theories and explanations for possible differences in intelligence. Last year Harpending and Cochran in "The 10,000 Year Explosion" came up with theories for Jewish intelligence and postulated that the Paleolithic explosion may have resulted from the admixture of Neanderthal genes. Voilà! Last week's science magazine published an article saying that Homo Sapiens strains which had left Africa may have up to four percent of Neanderthal genes. At any rate, this is where the exciting work is today, in teasing out why the differences exist, rather than confirming that they do.
In the last chapter of the book Miele draws Jensen out on the implications of his work, coming closer to public policy and politics than Jensen has previously ventured. Jensen hoped that public policy might be informed by his work. Unfortunately, just about the time of this book's publication George Bush promoted the "No Child Left Behind" act, a conspicuous and expensive failure now being compounded by the Obama administration, and California radically increased its spending on education also in the theory that more resources would make a difference. They did not heed Jensen.
Jensen advocates teaching each child as an individual, recognizing that they have very different capacities for absorbing learning. This is a good and useful observation. His suggestion that we use individualized computer delivered instruction to meet each child's individual needs shows that he is rather out of touch with the way children operate. Unfortunately, most children need teachers, and the less capable they are of learning, the more they need a concerned adults keep them on task. Computerized learning below the college level is for the most part wishful thinking. Especially this generation is far too easily distracted by the many time-wasting possibilities of computers.
Jensen expresses significant concern for the population explosion. In the eight years since publication it has become clear that world population growth is slowing almost everywhere. Jensen correctly observed a dysgenic function in the United States -- less intelligent people have more children. That same phenomenon exists worldwide. By my calculations, no nation on earth with an average intelligence in excess of 96 has a replacement rate above 2.1, the level required to maintain a stable population over the long term. Extrapolating, the world will have fewer and fewer capable people just as the demand for intelligent workers continues to expand. This can only exacerbate the differences between the rich and the poor, the Gini index gulf, and social unrest. Jensen's message is more important than ever.