Heritability intelligence

I distinguish between theoretical and practical conclusions because theoretically we are interested in the degree of genetic influence on a latent trait or theoretical construct. Practically we may be interested in the heritability of a specific measure (e.g., IQ as measures by the Wechler Adult Intelligence Scale). An excellent discussion of measurement eror in psychological research can be found in Schmidt and Hunter (1996). 

What, then, of the claim that individual differences in intelligence are subject to strong genetic influence We will hear summaries of findings from twin and adoptee studies indicating a substantial broad heritability. Most reviewers have put the figure somewhere in the 40—80% range (Hunt 1997, Waldman 1997) but, from both theoretical and practical perspectives, it matters little just where in that... 

The paradox of heritable variation for adaptive (and their logically necessary complement, maladaptive) traits applies more generally than merely to intelligence. Indeed, in the human behaviour genetics literature most traits are moderately heritable. (Elsewhere I have recommended the generalization that =0.40 0.20 as Bailey s Law [Bailey 1997].) This appears to be true even of traits associated with reproductive success, such as schizophrenia versus... 

Why is intelligence still heritable after all these years ... 

If the factor is subordinate to thef factor, then the surprisingly high heritability of human intelligence may reflect the heritability of fitness itself across many species. 

Brody So your argument is that there is no variation, but the preference for an intelligent mate is not itself heritable. 

Miller For my argument to work, there doesn t have to be variation in the sexual preference for intelligence, but I suspect there is variation, and I frankly would like to see more replications of the studies that find no heritable variation in human mate preferences. 

Miller In my paper in particular, what I am striving for is a theory of -loadings. I want to explain why some mental adaptations are so much more dependent on than others, and why some are more variable and heritable. If we can have a predictive theory which says which mental adaptations are and aren t, this is a step forward in understanding intelligence. 

Jacobs, N., Van Gestel, S., Derom, C., Thiery, E., Vernon, P., Derom, R., Vlietinck, R. (2001). Heritability estimates of intelligence in twins effect of chorion type. Behav. Genet. 31 209—217. 

There is little doubt that intelligence holds a genetic component although little, very little is known about the actual heritability of IQ, in a technical sense. A neuron contains 5000-10000 different proteins, and any relationship between the state of the corresponding genes and a given IQ must, if it... 

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