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The latest on intelligence

5/10/2012

 
You may remember The Bell Curve. The book was published in 1994 by Richard Herrnstein and Charles Murray, and it argued that IQ is largely determined by genetics and little by the environment. It further argued that racial differences in IQ tests scores were likely due to genetic differences among the races.

A media firestorm ensued, with most of the commentary issuing from people without the statistical and methodological background to address the core claims of the book.

The American Psychological Association created a panel of eminent researchers to write a summary of what was known about intelligence, which would presumably contradict many of these claims. The panel published the article in 1996, a thoughtful rebuttal of many of the inaccurate claims in The Bell Curve, but also a very useful summary of what some of the best researchers in the field could agree on when it came to intelligence.

Now there's an update.

A group of eminent scientists thought the time was ripe to provide the field with another status-of-the-field statement. They argue that there have been three big changes in the 15 years since the last report: (1) we know much more about the biology underlying intelligence; (2) we have a much better understanding of the impact of the environment on intelligence, and that impact is larger than was suspected; (3) we have a better understanding of how genes and the environment interact.

Some of the broad conclusions are listed below (please note that these are close paraphrases of the article's abstract).
  • The extent to which genes matter to intelligence varies by social class (genetic inheritance matters more if you're wealthy, less if you're poor).
  • Almost no genetic polymorphisms have been discovered that are consistently associated with variation of IQ in the normal range.
  • "Crystallized" and "fluid" intelligence are different, both behaviorally and biologically.
  • The importance of the environment for IQ is established by the 12 to 18 point increase in IQ observed when children are adopted from working-class to middle-class homes.
  • In most developed countries studied, gains on IQ tests have continued, and they are beginning in the developing world
  • Sex differences in some aspects of intelligence are due partly to biological factors and partly to socialization factors.
  • The IQ gap between Blacks and Whites in the US has been reduced by 0.33 standard deviations in recent years.
The article is well worth reading in its entirety. Download it here.

Neisser, U.; Boodoo, G.; Bouchard, T. J. , J.; Boykin, A. W.; Brody, N.; Ceci, S. J.; Halpern, D. F.; Loehlin, J. C. et al (1996). Intelligence: Knowns and Unknowns. American Psychologist, 51: 77.

Nisbett, R. E., Aronson, J., Blair, C., Dickens, W., Flynn, J., Halpern, D. F., & Turkheimer, E. (2012, January 2). Intelligence: New Findings and Theoretical Developments. American Psychologist, 67, 130-159.


Jane Campbell link
5/10/2012 05:58:26 am

I remember it well. Stephen J. Gould denounced some of the Herrnstein & Murray data outright. The point I still remember taking away from The Bell Curve was that we needed to let data speak, whatever good taste may recommend. Skeleton-in-my-closet disclaimer: Richard Herrnstein was on my thesis committee. I felt he could get a pass since he had cancer and didn't have long.

Gwern link
7/17/2012 04:01:54 am

> Stephen J. Gould denounced some of the Herrnstein & Murray data outright.

I suppose Gould *would* know about data fabrication...

DanielD
7/17/2012 06:27:24 am

Yes, he would. He fabricated some data himself

http://www.wired.com/wiredscience/2011/06/gould-morton-revisited/

Dan Willingham
7/17/2012 06:53:22 am

To be fair, the Wired article makes it more like Gould unconsciously biased his analysis because of how he wanted the data to come out. Hardly admirable, but different than out and out fabrication.

DC
7/18/2012 03:17:49 am

That's called "ad hominem". Does it invalidate Gould denunciation of data fabrication?

Gwern link
7/18/2012 03:29:09 am

DC, in the real world (as opposed to syllogisms and philosophy 101), ad hominem works and is a valid point to make, which is of course why Gould focused on the men and any dirt he could dig up on them, rather than, say, merely ignoring any data he thought they fabricated...

So let us say that I don't think accusations of data fabrication should be taken very seriously when in accusing people of biasing & fabricating data, Gould himself biased his data!

David Austin
5/10/2012 07:28:08 am

Nisbett et al might usefully have included Glymour's critique in their References:

Glymour, Clark. (1998). "What Went Wrong? Reflections on Science by Observation and the Bell Curve." Philosophy of Science, 65(1), 1-32.
http://www.hss.cmu.edu/philosophy/glymour/glymour1998.pdf
[another version appears as the last chapter of: Glymour, Clark. The Mind's Arrows: Bayes Nets and Graphical Causal Models, MIT Press, 2002.]

Cited in:
Cosma Shalizi, "Yet More on the Heritability and Malleability of IQ"
http://cscs.umich.edu/~crshalizi/weblog/520.html
Cosma Shalizi, "g, a Statistical Myth"
http://www.cscs.umich.edu/~crshalizi/weblog/523.html

Scott Johnson
5/10/2012 07:29:08 am

The proxy's involved in measuring intelligence are confounding. Imagine if the tests were all constucted on hip hop music knowledge, or ability to use social media. What if we measured one's apptitude at creating a delicious meal. All of these tests require apptitude of some ilk. Suffice to say that the intelligence tests measure something. Can we teach everyone to test well on these somethings with practice? Could, given adequate resources, anyone improve their respective score? The question should not be so much constructed around the scale of intelligence, but more does a high score on this test predict high or low achievement at doing this or that vocation. My 75 may be more than good enough to be the best chef in town. Your 142 may leave you in a lurch to interact profitably at your sales job. As with most of what we measure in Psychology, the questions we ask are often to singular in application.

I just watched the reconstruct of Milgrams studies on TV. The results he reported were replicated. Have we grown in the last 49 years, socially aware wise? Most of us think so. Does this replication prove we have not? Hardly. Intelligence scores have risen in certain areas of the world over the years. Why? Do the increases better predict performance, social growth, municipal philanthropy?

IQ is a measure of something, but so is barometric pressure. To what degree it applies is where the patient got off the couch.

El
7/17/2012 06:32:17 am

Please, if you're completely ignorant as to what IQ even is and how it's tested for, don't post your ignorant rants.

KW
7/17/2012 10:34:54 am

Don't belittle someone else without positing your own opinion for critique.

Tom Dee
5/10/2012 01:42:27 pm

Thanks for posting this, Dan. I cite the earlier report in my work on gender gaps and I didn't know it was updated. I was/am surprised by the evidence for some sex differences in intelligence.

Douglas Hainline
6/28/2012 12:11:40 am

Previous commenters have made variants of the following arguments: that IQ tests are culturally-biased ("what if we measured knowledge of hip-hop?"), or that they don't predict anything except your ability to score high on IQ tests, and may simply be the results of coaching.

There are some very good reasons to proceed with caution on this question, but neither of these arguments is among them. Anyone who wants to pronounce on this issue really should read the serious arguments from all camps.

A good, quick introduction to the question of IQ -- although the author wisely avoids the issue of race -- is Deary, I. J. (2001). Intelligence: A very short introduction. Oxford: Oxford University Press.

And a useful website is: http://www.indiana.edu/~intell/index.shtml

Brett Stevens link
7/17/2012 05:54:30 am

Most of this is measurement fallacy, much like Lewontin's and Gould's arguments. Naturally, this is in order to defend the dominant paradigm which is that nurture and not nature is important.

For example, we are not able yet to consistently measure intelligence by genes, but that does not mean the relationship does not exist.

JohnH
7/17/2012 06:48:11 am

No, that's either ignorant or obfuscating. In either case it misses the point that environment has been shown to have a large effect on IQ and that the effect is larger than any genetic effect we may someday discover.

Le Gup
7/17/2012 06:41:29 am

And all of these interesting observations leave out any discussion of the bias inherent in IQ testing toward a certain social class? Of course IQ goes up when a poor child is adopted into a wealthy family, because the IQ test itself is skewed and biased -- it was developed by a specific social class to test for the kind of intelligence valued by that social class!

phunctor
7/18/2012 01:00:25 am

Social class and the distribution of intelligence are aspects of a dynamic, coevolved system. Rightists impose an ideological arrow of causation in one direction, leftists another. Neither arrow helps to explain the phenomena. What guidance on policy follows from the causal claim doesn't need the data, it was there already in the ideology. I conclude such claims from either side are pure insidious spin.

Edwin Martin link
7/18/2012 01:33:29 am

This issue (together with culturally-biased tests) has been coined decennia ago and has been fixed since then.

I can't believe you can still find good, modern tests which are biased.

Juanmi
7/17/2012 10:21:30 am

With all due respect, but talking about intelligence: why or why can't Americans distinguish between the abbreviation "it's" and the possessive "its"?? In its entirety...

Phil
7/17/2012 11:01:53 am

Because the correct usage is counter intuitive and, mostly, irrelevant. Also laziness.

"talking about intelligence"? Really?

Dan Willingham
7/17/2012 11:12:14 am

Fixed. Thanks for noting the error.

Dan Tester link
7/17/2012 11:20:19 am

almost everyone knows that both genes and environment impact intelligence. to what extent of each, is the question.

for the first time women have higher IQ's then men, but this still doesn't mean that men are not genetically intelligent. a combination of negative social trends for men, + positive social trends for women could have finally caused this. (well , regardless of who might be 'genetically smarter' its the cause.)

David
7/17/2012 07:25:35 pm

This all assumes that "intelligence" can be measured and that IQ tests actually measure it. A very iffy proposition.

Michael McQuirk
7/17/2012 09:51:20 pm

I believe they're all wrong. Genes have almost nothing to do with one's IQ level. It's all to do with how you think, everyone thinks differently.

When you are a child your brain is still relatively new and your subconscious is still trying to make sense of the world. It is constantly trying to build a "model" of the world around you, and at this point it's still just laying the foundations. Everyone's model is different; you may think in a more visual and analytic way, building those sand castles in your head before getting your hands dirty. Others may be hands-on and experience driven; building castles, destroying them, building them up again differently...

The way a child's parents teach their child about the world drastically changes the way the child will view the world, obviously. If his/her parents are more of the creative sort, then it would make sense that the child would think like his/her parents and be more creative than analytical. This would explain the misconception that a child inherits their IQ through DNA. If a child's parents have high IQs then their child would be most likely be taught to model the world in a way that is in alignment with his/her parent's models, thus leading to a higher IQ. The opposite is also true, the lower a child's parent's IQs, the less likely they are to teach their child to think and experiment for themselves.

I'm no scientist, biologist or psychologist, that's just my opinion.

Edwin Martin link
7/18/2012 12:59:28 am

"I'm no scientist, biologist or psychologist, that's just my opinion."

Science is not an opinion. Science is measuring and getting facts as good as possible. Science is about leaving opinion out.


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