It was little consolation that I had been ‘in good company’ in my ignorance of genetics; in fact, that aspect of the situation seemed even more alarm… - Arthur R. Jensen

The key theme in Gordon’s chapter, that lends it theoretical coherence, is his clear perception that the guiding force in my own work in mental measurement arises principally from my constant search for construct validity that can embrace the widest range of phenomena in differential psychology. In my philosophy, science is an unrelenting battle against ad hoc explanation. No other field in psychology with which I have been acquainted has been so infested by ad hoc theories as the attempts to explain social class, racial, and ethnic group differences on various tests of mental ability. My pursuit of what I have called the Spearman hypothesis (Jensen, 1985a), which is nicely explicated by Gordon, represents an effort to displace various ad hoc views of the black-white differences on psychometric tests by pointing out the relationship of the differences to the g loadings of tests, thereby bringing the black-white difference into the whole nomothetic network of the g construct. It is within this framework, I believe, that the black-white difference in psychometric tests and all their correlates, will ultimately have to be understood. Understanding the black-white difference is part and parcel of understanding the nature of g itself. My thoughts about researching the nature of g have been expounded in a recent book chapter (Jensen, 1986b). Enough said. Gordon’s chapter speaks for itself, and, with his three commentaries on the chapters by Osterlind, Shepard, and Scheuneman, leaves little else for me to add to this topic.

The study of inbreeding depression seems to me especially important in the study of human abilities, because inbreeding depression indicates genetic dominance, and the presence and degree of dominance are related to natural selection for the trait in the course of its biological evolution. It was of great interest to me to discover, for example, that of the several ability factors that can be extracted from the various subtests of the Wechsler Intelligence Scale for Children, the one that shows the greatest susceptibility to inbreeding depression is the g factor (Jensen, 1983b). This finding indicates that one of our most widely used standard psychometric tests of intelligence yields scores that reflect some part of the variance in the biological intelligence that has developed in the course of human evolution.

[Interview: Responding to a question about whether it was smart to publish his 1969 article at the time he did] In retrospect, however, I would hope that I would not have changed a thing in that article, even if I had been able to imagine the supposed "storm" it caused. I will be ashamed the day I feel I should knuckle under to social-political pressures about issues and research I think are important for the advance of scientific knowledge.