Lots of stuff showing up on IQ and genetics these days. The New York Times has a story.

“Let’s say [hypothetically] the genetic data says we’ll have to spend two times as much for every black child to close the achievement gap,” said Jason Malloy, 28, an artist in Madison, Wis., who wrote a defense of Dr. Watson for the widely read science blog Gene Expression. Society, he said, would need to consider how individuals “can be given educational and occupational opportunities that work best for their unique talents and limitations.”

I’ve referred to Malloy’s long post previously–I recommend reading it if you have not already.The Cato Unbound discussion continues, with an essay by Linda S. Gottfredson. She writes,

people often confuse the yardstick (IQ scores) with the construct (g) actually measured. The manifest content of ability tests items provides no guide to the ability constructs they actually succeed in measuring. The active ingredient in tests of intelligence is the complexity of their items, and it is also the ingredient—“processing complexity”—in functional literacy tasks that makes some more difficult than others (more abstract, more distracting information, require inferences, etc.). To oversimplify only a bit, as long as two tests have similar g loadings, both will predict the same achievement equally well (or poorly), no matter how different their content might seem (Gottfredson, 2002).

You probably need to read her whole essay to grasp the point. Flynn theorizes that environmental influences have increased some test results more than others. It sounds like he is saying that there are different components of intelligence, and some of those components have been affected by environmental influences. She seems to be saying that the individual tests are all indicators of the same thing, not components of anything.

Economists used to construct–and I believe the NBER still maintains–indexes of leading, coincident, and lagging indicators. Things like stock prices, pig iron shipments, and wholesale prices supposedly behave differently depending on whether you are heading into, undergoing, or heading out of a recession. If it turns out that the components of, say, the index of leading indicators have separate trends, that does not tell you that something is changing about the frequency and duration of recessions. A recession is still a recession, no matter what set of indicators you use to predict it or how those indicators behave in terms of secular trends.

Finally, the American Enterprise Institute held a forum on a new book by Jon Entine on Jewish IQ. I did not attend, but I listened to the audio of the event which is available at the link. I got the sense that the evidence for a genetic basis of high average Jewish IQ is speculative and that various theories are inconsistent with one another. For example, Entine’s story has only Jews of Eastern European origin having the higher IQ, while Charles Murray wants to include Jews from Spain and Northern Africa.

Is it possible to talk about IQ and lose the we of group identity? There are all sorts of indicators of intelligence that have a high signal-to-noise ratio at an individual level. Ethnicity has a pretty high noise-to-signal ratio at the individual level. I do not see any justification for discrimination based on ethnic identity, given how easy it is to obtain other indicators.

Tim Harford’s next book has an interesting chapter on the dangers of using racial indicators. He cites work by Roland Fryer, Jacob Goeree, and Charles Holt. If I know that employers use color as a signal, and my color is a negative signal, then it may not pay for me to invest in education. Of course, if everyone of my color looks at it the same way, then none of us will invest in education, and now more employers will find color to be a useful signal. The authors created an experiment that shows how this sort of self-reinforcing discrimination can result in a world where the colors are purple and green, assigned to individuals at random.

So ethnic identity is a dangerous thing. But we seem to be really attached to it, and we seem to be really attached to using it as a signal.

It’s striking that popular discussions of IQ seem to quickly become discussions of race. Holding one’s individual intelligence constant, is there something happy about being a member of a high-IQ ethnic group and something sad about being a member of a low-IQ ethnic group? That’s the way a lot of people seem to react. I’m not sure why.