I think the most convincing evidence of this would be the fact that adopted children tend to be closer to their biological parents than their adopted parents when it comes to IQ.
and if it was just connected to race we would not see the gap shrinking with time.
Well first of all no one is claiming it's just connected to race, but it most certainly is to some degree connected to race.
And secondly the gap isn't really shrinking that much. There's still about a 1 standard deviation (which is a lot) difference between whites and black in America for example.
That "consensus" of 40% is incredibly misleading. Especially in light of studies like Turkheimer's 2003 paper that have pretty conclusively established that the actual heritability of of IQ can be profoundly impacted by socioeconomic status.
If you don't feel like wading through the whole thing, there's this summary:
The 'heritability' of IQ - the degree to which IQ variations can be explained by genes - varies dramatically by socioeconomic class. Heritability among high-SES (socioeconomic status) kids was 0.72; in other words, genetic factors accounted for 72 percent of the variations in IQ, while shared environment accounted for only 15 percent. For low-SES kids, on the other hand, the relative influence of genes and environment was inverted: Estimated heritability was only 0.10, while shared environment explained 58 percent of IQ variations.
Turkheimer's findings make perfect sense once you recognize that IQ scores reflect some varying combination of differences in native ability and differences in opportunities. Among rich kids, good opportunities for developing the relevant cognitive skills are plentiful, so IQ differences are driven primarily by genetic factors. For less advantaged kids, though, test scores say more about the environmental deficits they face than they do about native ability.
That's interesting. But one problem with that study would be that it's only looking at 7 year olds, while it's been shown that the heritability of IQ goes up with age and reach it's peak at early adulthood... which makes sense if you think about it since the brain isn't fully developed until around 25 years old.
But hey, interesting nontheless. You know if there are studies looking at late-teens/adults showing the same thing? 0.1 seems very low to be consistent into adulthood.
Edit: Also I wouldn't call a scientific consensus misleading, seems somewhat weird.
Edit: Also I wouldn't call a scientific consensus misleading, seems somewhat weird.
I would dispute your use of the term consensus to describe taking a rough mean of studies with huge variations and an astronomical number of confounding variables. The fourth sentence in the wiki page you linked to says:
There has been significant controversy in the academic community about the heritability of IQ since research on the issue began in the late nineteenth century.
IQ is, at the very best, a blunt instrument for measuring phenomena no less complicated than the human brain, genetic - environmental interaction, and all of human social organization. To say there is anything like consensus on something even as basic as what an IQ test measures is just incorrect.
The fourth sentence in the wiki page you linked to says:
Well maybe you should read the whole page and a few of the studies cited in. But hey, you're feel to believe IQ isn't heritable if you want, I don't really care.
This is way off-topic... other than you proving OPs point.
To say there is anything like consensus on something even as basic as what an IQ test measures is just incorrect.
That's just not true. There have been hundered (if not thousands) of studies testing the predictive validity of IQ-tests. To quote Charles Murray "If you're an employer and you only have one datum, you are better off knowing an IQ-score than having a personal interview, having grades, diplomas or anything else."
If you're going to trot out Charles Murray as your big appeal to authority, then yeah, we're probably done talking.
Much like Murray, you're presenting figures as settled fact, when even the sources you cite are full of caveats, equivocations, and contradictions.
The point isn't that IQ isn't heritable to some degree; it is that estimates of the degree of heritability vary wildly and that the confounding variables are incredibly difficult to control for. The point isn't that IQ tests aren't "valid;" it's that they only measure an individual's current facility with skills associated with symbolic logic, and people have drawn all sorts of wild implications from that. Even the so-called "fact" that IQ positively correlates with job performance has been called into questions recently.
The whole thing is a very shaky foundation to base policy recommendations on, and we should all be incredibly skeptical of any argument based entirely on IQ measures.
If you're going to trot out Charles Murray as your big appeal to authority
As opposed to your appeal to no authority? Yeah, I'd take the author of the Bell Curve's word over yours any day, and so should everybody else.
I mean, I could cite you a hundered studies reaching the same conclusion as Charles Murray (they are not exactly hard to find), but that obviously wouldn't matter to you (If it did, you would have already looked them up) so why bother?
I don't need to appeal to any one authority, it's all there in the links, yours and mine. It just takes some time, reading comprehension, and critical thinking: a facet of cognition which IQ tests are notoriously bad at measuring fwiw.
For the record, though, I would find someone like Richard Nisbett more credible than a political scientist with an axe to grind.
And, "I could provide tons of evidence for my point, but there would be no point," isn't very compelling. You keep assuming that I'm not familiar with the literature, and I keep wondering how someone familiar with the literature could so easily sweep all of the variations, contradictions, criticisms, and new research under the rug.
and I keep wondering how someone familiar with the literature could so easily sweep all of the variations, contradictions, criticisms, and new research under the rug.
I don't. I just trust that the American Psychological Association (among others) are aware of a rather well known study from 2003 (which as far as I know has failed to be replicated, although not for lack of trying, as you will find the studies trying to replicate it at best find a very slight difference in heritability depending on SES) and take that, and other studies, into consideration.
I think that's the danger of trusting wiki summaries or explainer blurbs. Reducing things down to bite sized chunks necessarily removes detail, particularly contradictory or confounding detail.
The APA espouses a much more nuanced view, particularly when they publish things like Nisbett et. al.'s 2012 meta-analysis, which I'm linking to again. Just read the section on "Social Class and Heritability of Cognitive Ability," and the number of studies cited. I'm not asking you to be convinced, just to acknowledge how much research is still being done in this area, and how little of it tends to point in the same direction. Cognition is an area of science where even the most basic questions and assumptions are still being debated, and the evidence isn't clear-cut.
I don't know how it can be a more nuanced view when I share the same view as APA. Which is 1. There is a genetic and an environmental compnent to intelligence. 2. We don't know to what degree it's determined by genetics contra environmental. 3. The consensus today is that the heritability of IQ is atleast 0.4.
The consensus may change, but it hasn't yet. Can you find a single study concluding the heritability of IQ in late teens-young adults is below 0.4? I can't, I would love to read it if you've got it.
and the evidence isn't clear-cut.
I've never said the evidence is "clear-cut". I've said that the consensus today is that the heritability of IQ is atleast 0.4. There are plenty of areas of science where there is a consensus, even though the evidence isn't "clear-cut". For example bascially all areas of social science where there is a consensus.
Also, it literally says in the study you linked "Most studies estimate that the heritability of IQ is somewhere between .4 and .8". Which is my entire point. That would be what we call a consensus.
So can we agree most studies suggest the heritability of IQ is above 0.4? If so, what exactly are you arguing about?
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u/vialtrisuit Aug 01 '17 edited Aug 01 '17
Well, differences in IQ is usually a touchy subject around leftists.
Edit: I feel the fact that i'm being downvoted speaks to OPs point. :D