IQ and success: Can a test score determine later outcomes in life?

Is IQ a Good Predictor of Success?

Is IQ a Good Predictor of Success?

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Sept. 19 2015 7:20 AM

Is IQ a Good Predictor of Success?

Keep studying, geniuses.

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Answer by Peter S. Magnusson, senior vice president, Cloud Development, Oracle; formerly Snapchat, Google, and Virtutech:


As the question is stated, the answer is simply “yes.” If you take a “real” IQ test (see comments below), then the result is a strong statistical predictor of multiple future life outcomes—income, education level, health, even longevity. There are loads of studies that confirm these correlations. So in that sense, it “predicts” your future “success.” However—and it's a big however—be careful what inferences you draw from this answer.

Don't equate IQ with intelligence. It's still a matter of, at times heated, debate as to what IQ actually measures. And it's also a complex conversation to discuss what we mean by intelligence. So think of IQ score as simply an abstract number that is statistically correlated with a bunch of other abstract numbers (such as future annual income). And beware of any philosophical, political, personal, and other conclusions you might jump to from the yes answer.

Pretty much none of the IQ tests that you have probably heard of or encountered have much validity. Online tests, apps, and popular test-your-IQ books are almost invariably not properly designed. I have yet to find a single one that is. To get a real IQ number, you need to take a test administered by and licensed to a professional by one of the major test publishing companies—tests such as Wechsler or Stanford-Binet. Note also that different tests are used for children, adolescents, and adults. Most online tests and their ilk are more or less scams to generate Web traffic.

An IQ score correlates with success but doesn't dictate it, and it is a poor “measure of the man.” Allow me to be politically incorrect for a moment to make my point: Saying that IQ scores predict success is a little like saying that the color of your skin at birth predicts your future income. You can see the problems: Causality is an issue, the significance of other factors is an issue, and so on.

More in the abstract, what we know about IQ correlations pertains to groups of people. These are statistical measures. Their relevance for an individual is difficult to evaluate at best. Another way of saying this is that whereas for a large group of people IQ is one of the strongest predictors of future success that we know of, for an individual, it is a weak indication. For example, in one large study correlating IQ and socio-economic status of parents with future income, IQ had a three-times higher “beta” than socio-economic status. That means how “smart” you are is much more important than who your parents are (the U.S. economy, in other words, is a relatively level playing field). However, the total R-squared of using both variables was only 0.14. That means that knowing the parents' socio-economic status as well as the child's IQ together only explained about 14 percent of the child's future outcome. From the perspective of the decisions available to that child, that's not a very big number.

So in other words, the answer to the questions is, strictly speaking, yes. But the footnote to bear in mind is: So what?

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