if someone can find the references for these, here are a few tid-bits from memory:

* the height-IQ correlation is not found within families, and thus appears to be due to assortative mating
* nutritional deprivation has a complex relationship to IQ, but some kinds of strong deprivation can have very little lasting effects (i.e. they are remediable); not sure about the comparable effects on height - a period of famine in euro during 20c (i think ca WWII) provides data for this as does East Asian adoption data
* according to the latest papers from Flynn, he doesn't think the Flynn effect has an impact on g, and thus the most-heritabile component of IQ scores are qualitatively different than the intergeneration change
* a heritabiltiy of 70%-80% among adults living in middle class, Western environments is now a consensus; the "range" in reported heritabilities is largely due to the fact that heritability increases with age (i.e. heritability is seemingly lower at younger ages)

one more:

iirc, Flynn is not very keen on the nutritional hypothesis for the Flynn effect, at least for gains in the 2nd half of 20c.

I've left some comments. They are "in moderation" and so haven't been posted yet ...

Neisser et al (1996) wrote:

Parameter Estimates. Across the ordinary range of environments in modern Western societies, a sizable part of the variation in intelligence test scores is associated with genetic differences among individuals. Quantitative estimates vary from one study to another, because many are based on small or selective samples. If one simply combines all available correlations in a single analysis, the heritability (h2) works out to about .50 and the between-family variance (c2) to about .25 (e.g., Chipuer, Rovine, & Plomin, 1990; Loehlin, 1989). These overall figures are misleading, however, because most of the relevant studies have been done with children. We now know that the heritability of IQ changes with age: h2 goes up and c2 goes down from infancy to adulthood (McCartney, Harris, & Bernieri, 1990; McGue, Bouchard, Iacono, & Lykken, 1993). In childhood h2 and C2 for IQ are of the order of .45 and .35; by late adolescence h2 is around .75 and c2 is quite low (zero in some studies). Substantial environmental variance remains, but it primarily reflects within-family rather than between-family differences.

These adult parameter estimates are based on a number of independent studies. The correlation between MZ twins reared apart, which directly estimates h2, ranged from .68 to .78 in five studies involving adult samples from Europe and the U.S. (McGue et al., 1993). The correlation between unrelated children reared together in adoptive families, which directly estimates c2, was approximately zero for adolescents in two adoption studies (Scarr & Weinberg, 1978; Loehlin, Horn, & Willerman, 1989) and .19 in a third (the Minnesota transracial adoption study: Scarr, Weinberg & Waldman, 1993).

These particular estimates derive from samples in which the lowest socioeconomic levels were underrepresented (i.e., there were few very poor families), so the range of between family differences was smaller than in the population as a whole. This means that we should be cautious in generalizing the findings for between-family effects across the entire social spectrum. The samples were also mostly white, but available data suggest that twin and sibling correlations in African-American and similarly selected White samples are more often comparable than not (Loehlin, Lindzey, & Spuhler, 1975).

Why should individual differences in intelligence (as measured by test scores) reflect genetic differences more strongly in adults than they do in children's One possibility is that as individuals grow older their transactions with their environments are increasingly influenced by the characteristics that they bring to those environments themselves, decreasingly by the conditions imposed by family life and social origins. Older persons are in a better position to select their own effective environments, a form of genotype-environment correlation. In any case the popular view that genetic influences on the development of a trait are essentially frozen at conception while the effects of the early environment cumulate inexorably is quite misleading, at least for the trait of psychometric intelligence.

Implications. Estimates of h2 and c2 for IQ (or any other trait) are descriptive statistics for the populations studied. (In this respect they are like means and standard deviations.) They are outcome measures, summarizing the results of a great many diverse, intricate, individually variable events and processes, but they can nevertheless be quite useful. They can tell us how much of the variation in a given trait the genes and family environments explain, and changes in them place some constraints on theories of how this occurs. On the other hand they have little to say about specific mechanisms, i.e. about how genetic and environmental differences get translated into individual physiological and psychological differences. Many psychologists and neuroscientists are actively studying such processes; data on heritabilities may give them ideas about what to look for and where or when to look for it.

A common error is to assume that because something is heritable it is necessarily unchangeable This is wrong. Heritability does not imply immutability. As previously noted, heritable traits can depend on learning, and they may be subject to other environmental effects as well. The value of h2 can change if the distribution of environments (or genes) in the population is substantially altered. On the other hand, there can be effective environmental changes that do not change heritability at all. If the environment relevant to a given trait improves in a way that affects all members of the population equally, the mean value of the trait will rise without any change in its heritability (because the differences among individuals in the population will stay the same). This has evidently happened for height: the heritability of stature is high, but average heights continue to increase (Olivier, 1980). Something of the sort may also be taking place for IQ scores the so-called 'Flynn effect" discussed in Section IV.

In theory, different subgroups of a population might have different distributions of environments or genes and hence different values of h2. This seems not to be the case for high and low IQ levels, for which adult heritabilities appear to be much the same (Saudino, Plomin, Pedersen, & McClearn, 1994). It is also possible that an impoverished or suppressive environment could fail to support the development of a trait, and hence restrict individual variation. This could affect estimates of h2, c2, Or both, depending on the details of the process. Again (as in the case of whole populations), an environmental factor that affected every member of a subgroup equally might alter the group's mean without affecting heritabilities at all.

Where the heritability of IQ is concerned, it has sometimes seemed as if the findings based on differences between group means were in contradiction with those based on correlations. For example, children adopted in infancy into advantaged families tend to have higher IQs in childhood than would have been expected if they had been reared by their birth mothers; this is a mean difference implicating the environment. Yet at the same time their individual resemblance to their birth mothers persists, and this correlation is most plausibly interpreted in genetic terms. There is no real contradiction: the two findings simply call attention to different aspects of the same phenomenon. A sensible account must include both aspects: there is only a single developmental process, and it occurs in individuals. By looking at means or correlations one learns somewhat different but compatible things about the genetic and environmental contributions to that process (Turkheimer, 1991).

As far as behavior genetic methods are concerned, there is nothing unique about psychometric intelligence relative to other traits or abilities. Any reliably measured trait can be analyzed by these methods, and many traits including personality and attitudes have been. The methods are neutral with regard to genetic and environmental sources of variance: if individual differences on a trait are entirely due to environmental factors, the analysis will reveal this. These methods have shown that genes contribute substantially to individual differences in intelligence test performance, and that their role seems to increase from infancy to adulthood. They have also shown that variations in the unique environments of individuals are important, and that between-family variation contributes significantly to observed differences in IQ scores in childhood although this effect diminishes later on. All these conclusions are wholly consistent with the notion that both genes and environment, in complex interplay, are essential to the development of intellectual competence.

http://search.bwh.harvard.edu/ co...EffectDraft.doc

I've linked the new Flynn paper a # of times. As Flynn notes:

a) the Flynn Effect is not g gains.

b) there is evidence against the Lynn Effect (i.e. nutrition being a predominate cause of the FE).

The idea that the nurture/nature debate for IQ hasn't moved since 1970 is preposterous. (highly doubtful that Quiggin has been "following" anything as he asserts) There have been several major twin studies and several major adoption studies. Behavior genetics and its methods have matured, and there have been numerous kinship studies. All the data substantially agree. Now of course were beginning to test and pin down genes.

"The idea that the nurture/nature debate for IQ hasn't moved since 1970 is preposterous." Is it? Most of what I read on the topic on this site agrees pretty well with what Eysenck said in his popular paperbacks in the sixties, doesn't it? To first order, I mean.

If I may go anecdotal:

I'm a 5.10 tall woman. I recognized rather quickly (in 70's) that I'm not exactly the "woman of men's dreams" - too tall, and a bespectacled serious intellectual ;-)), therefore the first thing I dropped from my wish list was the prospective groom's height, then the good looks. Howewer, I was firmly set NOT to sacrifice wits and wit in order to find a husband.

We should throw in a third long-term trend: the falling age of menarche.

I am neither a biologist nor a statistician but I deem surprising to never find any mention of vanishing tetrad differences when it comes to sort out causation from correlation.
Was the TETRAD Project from Spirtes, Glymour, and Scheines's Causation, Prediction, and Search such a bad idea or is it that "run of the mill" statisticians and biologists are not that much up to date?

Awww, shit, stupid Haloscan balks at 4 URLs, look for more info by yourself.

EW -- Tall and smart means "hot," at least for the enlightened among us.

Signed, Michael (a 5'9" bespectacled artsgeek married to a brainy blonde 6 footer)

Most of what I read on the topic on this site agrees pretty well with what Eysenck said in his popular paperbacks in the sixties, doesn't it?

Yes, but we have much more, and better quality data now.

I'm a 5.10 tall woman. I recognized rather quickly (in 70's) that I'm not exactly the "woman of men's dreams"

That's sorta true, but it's not quite that bad -- I'm going to post on the heights of sex symbols sometime today. They average 5'5.5, which is 1.5 inches above average.

Thanks for the help. The thing that I was most looking for was a handy literature summary to refute the claim that the "only significant new information in the last few decades" on intelligence and heredity is the Flynn Effect. My sense (I am no expert) is that a lot has been accomplished in the genetics of IQ in the last few years.) I tried to find a handy GNXP literature review post but couldn't locate one.

A pubmed search will turn up a number of putative genetic associations for IQ. One has to be cautious about these reports -- not because of IQ but because genetic associations are notoriously prone to false positives. A recent study was unable to confirm any of 85 putative associations with heart disease:

A study looking at 85 genetic variations thought to be linked to heart disease — some of which are already used in clinical tests — has been unable to confirm that any of these links are real.

However, at least one IQ association has been corroborated by multiple studies. As the power of genetic association studies improves, we can expect more.

JQ at Crooked Timber provides this. To my suggestion for another round.

DK, I’ve said my piece for now, but I’d be interested to read a GNXP view of the main developments in recent decades, taking account of the Flynn effect. If someone at GNXP wants to write something like this, I’ll certainly make some comments and may respond at greater length.

If I knew the literature better, I would do this myself. But I am just a dabbler.

Could someone do a post (or point me to one already done)? Help bring the good word of GNXP to the sheltered masses at Crooked Timber!