Demetriou's interesting discussion of g from his cognitive-developmental perspective distinguishes three facets of the g factor: biological, psychological, and subjective awareness of one's g. Jensen explains the essential difference between Demetriou's (2000) view and his own view (Jensen, 1998; 1999), which recognizes only two of Demetriou's facets.
2. Where I find it difficult to agree with Demetriou is in his idea that there is a subjective aspect to g. I could possibly be convinced of this, but at present I am not aware of any evidence that compels me to believe that we can be self-aware of our own level of g as a subjective experience. In other words, I don't think that a anyone who grew up alone on a desert island would ever become aware of what we mean by g, regardless of how intelligence they were. The individual would be quite self-aware of the variable amounts of effort expended on different tasks, the improvement in skills with practice, the increases in knowledge with experience, and the recall or forgetting of items of information. But how would the person experience the common factor, or g, in all these different abilities?
3. As soon as other persons came on the scene, however, the islander would begin comparing himself with others. By observing various persons in different learning and problem-solving situations, he would gain some impression of rather general performance differences among people in these situations and he could roughly rank-order them in 'general ability.' And he would probably have a fair idea of where he himself stood among the others in this respect. So there would be some degree of correlation between people's ranking of their own ability or cleverness and other people's ranking of them, and these ranks would probably be somewhat correlated with these persons' g factor scores -- if they could be obtained by a psychometrician who administers a large battery of diverse tests to all of the island's inhabitants.
4. But this very rough awareness of one's own g level is merely inferred from objective knowledge gained through the observation of other people's cognitive-related behavior in comparison with one's own; it is not acquired through introspection or subjective feelings about oneself. It is socially acquired knowledge. This might explain why parents have a less accurate impression of their child's IQ than does their children's teacher, who has a wider sampling of the range of children's abilities. The child with an IQ of 100 who seems average to the parents in one family may seem bright to the parents in another family, or dull to parents in still another family. Because of the limited social circles most people move in, they tend to judge themselves as closer to the average of the general population than they actually are.
5. I have interviewed persons (none of them psychologists) from every segment of the IQ distribution abut their estimates of their own IQ. Most people seem to know on which side of the population mean they fall, but those in the extremes greatly underestimate their extremity, especially at the high end of the distribution. Extraordinary achievements are typically attributed to interest, effort, and persistence. However important these factors might be, there is typically little awareness of the level of cognitive ability without which individuals' achievements would have been impossible, regardless of their effort and persistence. Even Richard Wagner was said to have at times felt depressed for his deficiency of musical talent because of the tremendous effort he had to muster while creating some of the musical miracles for which he became recognized as one of the world's great geniuses.
6. I agree that the level of g shapes important aspects of a person's everyday life; for example, interests, tastes, activities, self-concept, ethical sense, self-regulation, planfulness, delay of gratification, conscientiousness, openness to experience, law-abidingness, accident proneness, health, and longevity [see Chapters 9 and 14 in 'The g Factor' (Jensen, 1998)]. Many such characteristics are correlated somewhat with g, and variation in the level of g probably causes some of the variance in many of these traits.
7. Demetriou (2000, par. #6) suggests that g even contributes to its own further development in the individual by the projection of the sense of information-processing power into the individual's self concept. I doubt that g itself can be increased in this way. Rather, I think that a higher level of processing power, which is reflected by g, permits the individual to learn or master more different areas of knowledge and skill -- those aspects of ability that form the first-order factors and, at the second order, crystallized abilities (Cattell's Gc). This is consistent with Spearman's law of diminishing returns (Jensen, 1998, Appendix A), which Spearman formulated to explain the finding that g accounts for a larger proportion of the total variance in a battery of tests for persons in the lower half of the distribution of g than for persons in the above-average level of the g distribution. In groups of people with high levels of g, relatively more of the variance in test scores lies in the lower-order group factors and in test specificity. Higher g persons tend to invest their g in a greater variety of intellectual activities and interests than lower g persons; that is, cognitive abilities are more differentiated at higher levels of ability. Analogously, wealthy people spend their money on a greater variety of things than do poor people.
8. I believe that levels of g can facilitate the development of specific intellectual skills through learning and practice. But it is hard to imagine how the level of g could increase by feeding on itself, so to speak, or how to test empirically whether such a phenomenon actually occurs. Rather, I think it more probable that the level of g-loaded cognitive processes increases developmentally through the maturation of the physiological anlage of g. I am presently preparing a study for publication which shows that it is mainly the g component of various cognitive tests, rather than their specific knowledge contents or parfticular skill demands, that systematically increases developmentally with increasing age during childhood.
Demetriou, A.(2000). Self-awareness and the psychological marking of g. PSYCOLOQUY 10(002) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/2000.volume.11/ psyc.99.11.002.intelligence-g-factor.23.demetriou http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?11.002
Jensen, A.R. (1998). The g factor: The science of mental ability. Westport, CT: Praeger.
Jensen, A.R. (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