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July 23, 2012

Fun Facts About IQ

Since we're talking about the meaning of IQ scores today, here's some more grist for the mill:

Via The Social Animal: The Hidden Sources of Love, Character, and Achievement:
The single strongest predictor of a person’s IQ is the IQ of his or her mother.

We had never heard this before, but as a mother of two brilliant sons we're more than happy to take full credit :p

[drum roll]

Also interesting:
However, once you get beyond the school environment, it’s not a very reliable predictor of performance. Controlling for other factors, people with high IQs do not have better relationships and better marriages. They are not better at raising their children. In a chapter of Handbook of Intelligence, Richard K. Wagner of Florida State University surveys the research on IQ and job performance and concludes, “IQ predicts only about 4 percent of variance in job performance.” In another chapter of the handbook, John D. Mayer, Peter Salovey, and David Caruso conclude that at best IQ contributes about 20 percent to life success.
And:
One famous longitudinal study known as the Terman study followed a group of extremely high-IQ students (they all scored 135 or above). The researchers expected these brilliant young people to go on to have illustrious careers. They did fine, becoming lawyers and corporate executives, for the most part. But there were no superstar achievers in the group, no Pulitzer Prize winners or MacArthur Award winners. In a follow-up study by Melita Oden in 1968, the people in the group who seemed to be doing best had only slightly higher IQs. What they had was superior work ethics. They were the ones who had shown more ambition as children.

Hmmmm... that last study doesn't seem to bode well for the theory that higher proportions of males in the top 5% of the bell curve explain The Patriarchy, does it? :p

This was interesting, too:

The Flynn effect has always been tinged with mystery. First popularized by the political scientist James Flynn, the effect refers to the widespread increase in IQ scores over time. Some measures of intelligence — such as performance on Raven’s Progressive Matrices in Des Moines and Scotland — have been increasing for at least 100 years. What’s most peculiar is how scores have increased:

1) Scores have increased the most on the problem-solving portion of intelligence tests.
2) Verbal intelligence has remained relatively flat, while non-verbal scores continue to rise.
3) Performance gains have occurred across all age groups.
4) The rise in scores exists primarily on those tests with content that does not appear to be easily learned.

What’s puzzling about this increase in general intelligence is that it appears where we’d least expect it. While one might assume that IQ scores could increase over time in terms of crystallized intelligence — the part of the test that measures particular kinds of knowledge, such as being able to count or vocabulary words — it’s actually increased on measures of fluid intelligence, which is the ability to solve abstract problems. This has led some psychologists, such as Ian Dreary, to conclude that “large differences in scores [between generations] are demonstrated in just those situations where similarity would be expected.” Flynn, meanwhile, marveled at the magical constancy of the effect: “It’s as if some unseen hand is propelling scores upward,” he wrote.

There is, of course, no unseen hand. In recent years, many psychologists have embraced the “multiplicity hypothesis” which argues that the Flynn effect is explained by a long list of factors, such as improvements in early education (especially for girls), removal of lead paint, increased sophistication of tests, better test taking attitudes and adequate nutrition.

However, despite the flurry of interest in the Flynn effect, one lingering question has remained unanswered: Does the effect apply to everyone? More specifically, does it apply to the right tail of the ability distribution, or those 5 percent of individuals who score highest on the IQ test? What makes this mystery particularly noteworthy is that many of the explanations for the Flynn effect seem particularly relevant to the left side of the bell curve, or those with below average scores. This suggests that most of the intelligence gains have come from solving low hanging fruit, fixing those glaring societal inequalities that meant millions of children lacked access to adequate food, education and medical care. Since we’ve made progress on these problems, one might suppose that the Flynn effect would start to fade, at least in developed nations. (All the low hanging fruit is gone, as Tyler Cowen might say.) Sure enough, some studies have concluded that the Flynn effect has begun to disappear in Denmark, Norway and Britain.

A brand new study, “The Flynn Effect Puzzle,” currently in press at Intelligence, and led by Jonathan Wai at Duke University, has found an interesting way to assess the right tail of the distribution. By looking at approximately 1.7 million scores of 7th grade students between 1981 and 2000 on the SAT and ACT, as well as scores of 5th and 6th grade students on the EXPLORE test, the psychologists were able to investigate the extent to which the Flynn effect exists in the right tail of the bell curve. The results were clear:

The effect was found in the top 5% at a rate similar to the general distribution, providing evidence for the first time that the entire curve is likely increasing at a constant rate. The effect was also found for females as well as males, appears to still be continuing, is primarily concentrated on the mathematics subtests of the SAT, ACT, and EXPLORE, and operates similarly for both 5th and 6th as well as 7th graders in the right tail.

In other words, the Flynn effect doesn’t appear to be solely caused by rising scores among the lowest quartile. Rather, it seems to be just as prevalent among the top 5 percent. The smartest are getting smarter.

Posted by Cassandra at July 23, 2012 05:03 PM

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Comments

The single strongest predictor of a person’s IQ is the IQ of his or her mother.

But this is a self-evidently evidenciary. The IQ gene resides solely in mitochondrial DNA.

Eric Hines

Posted by: E Hines at July 23, 2012 06:16 PM

I have long thought that tne ability to get along with others is the most important thing in the workplace. Sure you have to produce but if you can't get along with people ...

Posted by: Bill Brandt at July 24, 2012 08:37 AM

Interestingly enough, I read somewhere that the #1 fear of employers is hiring someone who doesn't work and play well with others.

Posted by: Cass at July 24, 2012 08:53 AM

The Terman study doesn't surprise me. I think we as a society place far too much emphasis on intelligence. Hard work, perseverance, self-discipline and the ability to delay gratification are much, much more important to success in life. And generally no matter how smart you are, you won't get anywhere if you don't have the other qualities. I've watched this play out in my own family to painful effect.

Posted by: colagirl at July 24, 2012 09:51 AM

By the same token, imaging you're running a cutting-edge research lab. It's crucial for people to get along, but you're not going to get far with a crew of amiable buddies of average intelligence.

I don't think we can always say which single characteristic is most important. There may be a handful of them we can't do without. Don't workers have to be honest, too? And able to communicate? And not too easily discouraged by setbacks?

Posted by: Texan99 at July 24, 2012 10:02 AM

I would say that intelligence likely works as a minimum requirement. It's a necessary, but not sufficient condition.

That is, if you have a job that requires an IQ of 125, the guy with an IQ of 100 isn't going to succeed regardless of his other qualities. The gap is just huge. But between a person with an IQ of 135 and 160, even though there is the same 25 point difference in intellegence it'll be all the other qualities that matter. The gap in intellegence just isn't that big.

I can't tell you the number of brilliant people I've "failed" in an interview for the following:

Me: Alright, you built your statistical model, what did you learn.

Candidate: Well, we learned that X is a significant contributor to Y at the alpha=0.05 level.

Me: Ooooohhhhkayyyyyyy. But now that you know that, what did you do with that knowledge?

Candidate: I gave it to my manager.

Me: *facepalm*. But what part of the business did you change, or not change, based on this work?

Candidate: I don't know what he did with it.

Me: *headdesk* Alright, I've asked all the questions I need, do you have any questions for me? (Please.Dear.God.Say.No!)

Brilliant mathematicians, but dumb as a sack of hammers: "I just pound nails, it's not my job to know why nails need pounding".

Posted by: Yu-Ain Gonnano at July 24, 2012 12:33 PM

I work with metrics, and it never ceases to amaze me how many otherwise intelligent people will quote a number (or benchmark against it, or use it for decision making) without ever stopping to ask:

1. What does this number mean? (i.e., what can it tell me, and what can't it tell me?).

2. Was it collected using the same standards and definitions we use? Because if it wasn't, we're comparing apples and oranges.

Kind of scary.

Posted by: Cassandra at July 24, 2012 12:38 PM

The difference between the 135 and the 160 will become critical in some jobs. I'm no appellate-law specialist myself, but I know how smart the really good ones are, and there's no substitute for that extra edge. Ditto if you're the brains behind something like the Manhattan Project. The pretty-darn-smart guys aren't going to make up the difference with good work habits and people skills. That kind of job is rare, which is a good thing for jobs that have to be filled with people four standard deviations off the mean. Sometimes you need the high octane, and nothing else will do.

It reminds me of a friend from long ago, a really brilliant fellow. Good guy basically, but he'd drive you mad. His supervisor at Sandia Labs complained once that he didn't like his attitude. "It's a good thing you didn't hire me for my attitude," he replied. That guy could solve problems at a glance that very bright people simply beat their heads against in futility.

Posted by: Texan99 at July 24, 2012 01:12 PM

The difference between the 135 and the 160 will become critical in some jobs.

Well, yes. When the minimum cut off is 150 it certainly will. But I think you missed the generalized point.

Not all jobs will have the same cutoff. Some jobs will be higher and some will be lower. But once you have reached the threshold for that particular job, whatever it is, IQ suffers quickly from decreasing marginal utility, especially compared to other traits.

If you are a fan of The Big Bang Theory, imagine yourself as an accountant working next to Sheldon Cooper (were he do deign to stoop so low as to be an accountant). The marginal gain in IQ just isn't worth it.

Posted by: Yu-Ain Gonnano at July 24, 2012 02:12 PM

Oh, I completely agree with you there. The excess IQ is as likely to be a problem as a benefit.

Posted by: Texan99 at July 24, 2012 07:39 PM

What is interesting to me is the tendency to say that 'with a high IQ, anything is possible,' without saying what or how to get there.

Do you think that people with a high IQ think that because they are told they have one, things will come easy for them?

Posted by: Carolyn at July 26, 2012 12:27 AM

It's not that the IQ guarantees a result -- especially not a result without effort -- just that for some tasks it's a necessary condition.

We've probably all known very bright people who couldn't get along in the world or be much use to anyone. IQ alone won't make the world drop into their lap. But similarly, luck, pluck, and sterling personal qualities won't win a Nobel Prize.

Posted by: Texan99 at July 26, 2012 09:13 AM

The single strongest predictor of a person’s IQ is the IQ of his or her mother.


The father's IQ is just as good a predictor as the mother's. It's just that there's many more data on mothers and children.


Controlling for other factors, people with high IQs do not have better relationships and better marriages.


Not true. For example, higher-IQ people are less likely to divorce (see e.g. Murray and Herrnstein's analysis in The Bell Curve).


In a chapter of Handbook of Intelligence, Richard K. Wagner of Florida State University surveys the research on IQ and job performance and concludes, “IQ predicts only about 4 percent of variance in job performance.”


False. IQ explains about 25 percent of the variance in job performance. It's the single best predictor of job performance.


The researchers expected these brilliant young people to go on to have illustrious careers. They did fine, becoming lawyers and corporate executives, for the most part. But there were no superstar achievers in the group, no Pulitzer Prize winners or MacArthur Award winners. In a follow-up study by Melita Oden in 1968, the people in the group who seemed to be doing best had only slightly higher IQs.


The results of the Terman study are contradicted by a newer and larger longitudinal study, the Study of Mathematically Precocious Youth (SMPY). They found that high IQ in childhood predicted many later creative achievements, including literary and scientific works published and patents granted. The relationship between IQ and creativity persists throughout the IQ range, i.e., there is no threshold above which more IQ is not associated with more creativity. The SMPY's results are different from the Terman study probably because America has become more meritocratic since Terman's days.

Posted by: J at July 30, 2012 08:53 AM

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