| | I'm almost ready to let this sleeping dog lie, but in post 254, Brad remarked:
Nisbett's book was examined carefully and discredited thoroughly in "Race and IQ: A Theory-Based Review of the Research in Richard Nisbett’s Intelligence and How to Get It" But a thorough discreditation would not involve:
1) a large concession to your intellectual opponent (from your previous position)
2) continued misinterpretation of data
3) overt misrepresentation of your intellectual opponent
I've taken a little bit of time to view the .pdf file Brad offered in post 254, and I dare say that J. Phillipe Rushton and Arthur Jensen are guilty of the 3 transgressions listed above.
1) Jensen was one of the earliest "strong hereditarians" with regard to the causal factors that create someone's performance on an IQ test. Four decades ago, he said IQ was 75% genetic. As far as I can tell, he had not moved from that position for the remainder of the 20th Century (and even into the beginning of the 21st Century). But now, in a piece supposedly discrediting Richard E. Nisbett's book, Intelligence and How to Get It, all of a sudden that high number for heritability has dropped from 75% down to 50%. That, to me, appears to be a large concession. Now, large concessions aren't -- in themselves -- bad things. They are often proof of mature or refined thinking. But one thing that can make a large concession bad, is when it is done during a discreditation (when you are supposedly refuting someone else's rival position).
Let's imagine an example. Let's say that Harry and Sally are arguing. Harry says that men -- using spatial reasoning skills -- can shoot moving objects (e.g., as when hunting) 140 times better than women can because men have an extra 140 grams of brain tissue over-and-above what women have. Sally counter-argues that you can't look at the 140-gram difference in mean brain weights between men and women and then say that each and every gram-increase causes another full multiplier in hunting superiority. She says that it is just simply not the case that men are 140 times better at hunting than women. Then Harry moves into his position to attempt to discredit her:
You can't argue against my theory that extra brain matter causes improved hunting skills. Did you notice that? Did you notice that shift? First, Harry thought he had it all worked out, that for every extra gram of brain tissue, that men would -- additively -- become 100% better at hunting. But then, just when he is about to discredit Sally, all of a sudden his position is watered-down to the point of almost being irrelevant. That's a rhetorical transgression. I'm not sure if this rhetorical tactic has a name, but I think a good one might be: reverse straw man. Instead of casting your opponent's argument into something so absurd that it can be easily knocked down, it involves casting your position differently, so that it is no longer as logically unsupportable as it used to be (and, in the case of Jensen's position that IQ is 75% genetic, as it "used to be" for literally decades).
That's transgression #1.
2) In a graph depicting the estimated proportions of the total IQ variance attributable to genetic and environmental effects (Fig. 4, p. 19), Rushton and Jensen present data where genetic effects increase and where shared environmental effects drop to zero as people surpass age 20. This is a conceptual mistake. First of all, it only includes additive genetic effects while omitting non-additive effects (which both have to be held together, or integrated, during any correct interpretation of data), and therefore overestimates the overall genetic effect. Secondly, shared environmental effects are firstly environmental effects and only secondly are they shared. Yet Rushton and Jensen treat them as primarily things experienced during a shared process and only then -- as a mere artifact of this misconceptualization -- does it then appear to (indeed, it must appear to) approach zero as people move out of a shared environment with one another.
Let's imagine an example. Billy and Johnny are raised by Trudy and Bob Remington. They are brothers. In the shared environment that is their household growing up, they are exposed to high amounts of dietary fish. The Remingtons are peso-vegetarians ("fish" vegetarians) and they choose to raise their 2 sons that way, giving their sons copious amounts of fish for protein (indeed, as the primary source of protein). This shared fact of the matter -- that both sons eat a lot of fish -- affects IQ scores. Now, according to Rushton and Jensen, when the sons grow up and leave the home, they will no longer share this environmental factor. Why? Well, because they aren't in the same house anymore. Under this reasoning, if they don't share their meals at a common dinner table at a common time, then the factor drops out of the IQ equation. But is that the reality?
No.
What is infinitely more likely to happen here is that both of the sons do continue to eat some fish -- in some form or fashion -- even after leaving the home and going off to live separately. In other words, that factor that was a part of a shared environment growing up remains a relevant factor even outside of the original, shared environment. At the very least, as a factor influencing IQ, it does not drop all the way down to zero as Rushton and Jensen propose in Fig. 4.
That's transgression #2.
3) On page 31 of the document, Rushton and Jensen say this:
in [Nisbetts's] discussion of the adoption and heritability studies of young children showing how malleable IQ can be, he neglected to inform his readers that these effects are known to dissipate by late adolescence But that is a gross misrepresentation. In fact, Nisbett was very careful to make mention of how the adoption- (i.e., environment-) driven malleability of IQ dissipates with age. The first mention of heritability of IQ in adoption is mentioned in the index, starting at page 23 in the book. Just 2 pages later, at page 25, the careful mention of how environmental malleability seems to dissipate with age proceeds as follows:
Jensen and other strong hereditarians, however, would not accept a figure for between-family environmental effects that is as high as .20 to .26. This is because when people older than those in the studies summarized in Table 2.1, who are mostly children, are examined, the correlations drop dramatically--sometimes to as low as zero. This is true, for example, for unrelated children brought up in the same household. When they are adults the correlations run in the vicinity of .05 or less. The usual explanation given for this weak effect on adults is that as people grow older, they select their own environments, and their preference for one environment versus another is largely influenced by genetics. The importance of the early environment, never all that great to begin with, drops way off. And, if that is not enough, Nisbett repeats the point 5 pages later on page 30:
Stoolmiller calculated that if you correct for this restriction of environmental range, as much as 50 percent of the variation in intelligence could be due to differences between family environments. Since we know that within-family variation also makes an important contribution to IQ, this would mean that most of the variation in IQ is due to the environment. (These numbers would hold, though, only for children. We know that heritability goes up with age to some degree, so Stoolmiller's estimate for the contribution of between-family differences has to be lowered by some unknown amount.) Now, a counter-argument from Rushton and Jensen might be that there is "some place" somewhere later on in the book where Nisbett neglected to re-"inform readers that these effects are known to dissipate by late adolescence" but that is dropping the context. The context is already set. The cat is already out of the bag. Nisbett started off the conversation by admitting that environment effects and malleability dissipate with age. So, if at some later time he fails to exercise the unrelenting diligence to go ahead and repeat that very same point -- each and every time he returns to make mention of some or another adoption study, or some or another heritability study, or some or another malleability study -- if Nisbett fails to repeat himself ad nauseum, then he should not be held accountable for that. Holding someone accountable to repeat themselves, and to go on repeating themselves -- as if you somehow cannot remember how they began by stating the limitations in the first place -- is just flat-out wrong.
That's transgression #3.
So Brad is wrong in that the work performed by Rushton and Jensen does not amount to what it is that can be rightfully referred to as careful, thorough, and discrediting.
Ed
(Edited by Ed Thompson on 7/15, 12:17pm)
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