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Rain comments on Undiscriminating Skepticism - Less Wrong
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Ok, I summarized my views here:
http://fortaleza84.wordpress.com/2010/03/16/the-race-and-iq-question/
I'm happy to go into more detail; to answer questions; and to respond to arguments if you wish.
From what I can tell of your blog post, you said, "there's evidence, it's so obvious, people have alternative explanations but they're bogus, there's evidence, I bet whites do better than blacks on tests, there's tons of evidence."
Where's the evidence?
Here's Rushton and Jensen making their best case for significant genetic influences on intergroup differences in a 2005 review article, and a critical response from Richard Nisbett, one of the leading proponents of the hypothesis that there are no significant B-W genetic differences. Taken together, they are much more informative than selective presentations by amateurs.
I find Nisbett's reply pretty convincing. How do others feel?
Brazil, would you like to reply to the Nisbett article?
Not to excuse the shoddy scholarship of rushton and jensen, but I'd just like to add that a cursory examination of the nisbett article indeed shows some highly dubious claims. In several places he assumes a hypothesis of the form "If the hereditary model is true, then we should see X". But for many of these it seems that X does not necessarily follow from the hereditary hypothesis. the hereditary hypothesis is not a monolithic structure. it is a spectrum of correlation from 0.0 to 1.0. both ends seem equally implausible to me.
My own encounter with Nisbett material: http://news.ycombinator.com/item?id=4257220
Yes, I took the look at the article. I agree that if it's a correct summary of the evidence, it undermines my position.
Obviously I don't have time to run down every reference in the article, so I looked at the very first section, went to the web site of the what the author referred to as the "largest study," and looked at the very first graph I could find showing the gap in scores.
I'm telling you this so that nobody can accuse me of cherry picking. The graph I pulled up was the only data I retrieved which is referenced in the paper. Here is the graph:
http://nationsreportcard.gov/ltt_2008/ltt0005.asp
Just eyeballing it, it does not appear to support Nisbett's claim. It appears to show a small narrowing of the black/white gap between 1973 and 1982 and a fairly consistent gap thereafter.
So to put it politely, I am skeptical of the entire article.
You appear to be referring to Nisbett's paragraph starting with
A few sentences below that Nisbett refers to NAEP data to say that the reading score gap could be gone in 25 years and the science score gap in 75 years, if trends continue. [ETA: this is the 'largest study' that Nisbett cites. I'm sad Nisbett didn't give a more specific citation for it.]
The page you link appears to have data on the NAEP tests, but only for the mathematics tests. Clicking on the 'White-Black Gap' button, and then on the 'Age 17' tab (as Nisbett refers to 12th graders, so I am guessing that is what he and you are talking about...?) shows
The data linked do not appear to bear strongly on Nisbett's claims about the NAEP data (because Nisbett refers to the reading and science NAEP scores, not math), and I am also having difficulty seeing the 'small narrowing of the black/white gap between 1973 and 1982 and a fairly consistent gap thereafter.' in the data linked.
All in all, I am having difficulty substantiating your claim that Nisbett's claim is unsubstantiated by the data. I suspect either I am not interpreting your comment correctly, or the link in it happens to point to a data set other than the one you intended. Could you clarify?
(About the bigger question of whether black-white IQ differences have narrowed recently, it may be informative to read William Dickens and James Flynn's 2006 paper, which takes IQ test norming data and shows a narrowing of the IQ gap between 1972 and 2002. (Rushton and Jensen disagreed with the conclusions of that paper, but I find Dickens and Flynn's rebuttal convincing.)
I chose it at random and stopped with the first graph I found so nobody could accuse me of cherry picking. Looking more carefully at what Nisbett wrote, I see he did not specifically mention math scores.
I'm not sure if this makes a difference. If Nisbett was cherry-picking data, it doesn't really help his argument.
The one graph I looked at at random doesn't seem to support the claim that the gap (generally speaking) is narrowing and headed towards disappearing. Agreed?
When I see your random graph, I see the gap halving[!] from 1973 to 1990, widening through the 1990s, and maybe gradually shrunking since then. I see contradictory trends over the past 40 years, but it's more likely than not that the gap has resumed narrowing. So I'm not sure I do agree with you.
Since you write 'generally speaking' I guess you might be asking about the general trend as a whole from 1973 to now. I reckon that's an overall shrinking trend too.
To check my gut feeling more systematically, I did a quick regression of the score gap against year. (Not the best way to do it, but it beats eyeballing.) That gets me a .35 or .36 point shrinking per year depending on which assessment format I use for 2004. At that rate, the current gap (26 points in '08) would disappear in 70 to 75 years.
That's the same time period Nisbett gives for the disappearance of the science score gap, which I think is evidence against Nisbett 'cherry-picking' - if he cut out data because it had gaps that closed too slowly for his hypothesis, he would've left out the science data as well as the math data.
Summing up, I think I fundamentally disagree with you on the most likely interpretation of your graph.
Say what? The gap is 35 points in 1973 and 27 points in 1990. How is this halving?
Aha, I misunderstood which chart you had in mind. I thought that your link was intended to go to the data for 17 year olds, but that you were unable to link it directly because the page used Javascript to flip between the charts for different ages. I see now I'm wrong about that - one can link directly to the chart for each age, and it sounds like you were pointing to the age 9 data.
So I'll try this again with the 9 year olds. I've taken the liberty of looking at the black-white gap graph instead of the scale score graph so I don't have to do any mental arithmetic to get the gap size at each testing. Looks to me like the gap consistently narrowed from 1973 to 1986, and has fluctuated from 1986 so it's sometimes wider, sometimes thinner, but no overall trend since then.
Regressing gap size on year like I did before gives a shrinking of .24 or .25 points per year. So the picture is more mixed than for the older kids: there's an overall shrinking, but it's only two-thirds what you get for 17 year olds, and the trend looks like it's stalled since the late 80s.
Still, I am not sure that this means Nisbett is wrong. Looking at the bit of Nisbett you quote yourself downthread, Nisbett does not seem to say anything about the math scores, which means looking at the math scores would not tell us whether Nisbett is wrong or right.
It is possible that Nisbett cherry-picked by ignoring the math data, but I think a .25 point per year narrowing is still evidence against that idea. At a quarter point per year, the math gap would disappear in about a century, which isn't much longer than the 75 years Nisbett suggests for science.
You're looking at age 9, cupholder is looking at 17.