What do SAT and IQ tests measure? General intelligence predicts school and life success.

IQ Tests and the SAT Measure Something Real and Consequential

IQ Tests and the SAT Measure Something Real and Consequential

The state of the universe.
April 14 2014 11:54 PM

Yes, IQ Really Matters

Critics of the SAT and other standardized testing are disregarding the data.

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Thus, just as it was originally designed to do, the SAT in fact goes a long way toward leveling the playing field, giving students an opportunity to distinguish themselves regardless of their background. Scoring well on the SAT may in fact be the only such opportunity for students who graduate from public high schools that are regarded by college admissions offices as academically weak. In a letter to the editor, a reader of Elizabeth Kolbert’s New Yorker article on the SAT made this point well:

The SAT may be the bane of upper-middle-class parents trying to launch their children on a path to success. But sometimes one person’s obstacle is another person’s springboard. I am the daughter of a single, immigrant father who never attended college, and a good SAT score was one of the achievements that catapulted me into my state’s flagship university and, from there, on to medical school. Flawed though it is, the SAT afforded me, as it has thousands of others, a way to prove that a poor, public-school kid who never had any test prep can do just as well as, if not better than, her better-off peers.

The sort of admissions approach that Botstein advocates—adjusting high school GPA “to account for the curriculum and academic programs in the high school from which a student graduates” and abandoning the SAT—would do the opposite of leveling the playing field. A given high school GPA would be adjusted down for a poor, public-school kid, and adjusted up for a rich, private-school kid.  


Furthermore, contrary to what Boylan implies in her Times piece, “preparatory crash courses” don’t change SAT scores much. Research has consistently shown that prep courses have only a small effect on SAT scores—and a much smaller effect than test prep companies claim they do. For example, in one study of a random sample of more than 4,000 students, average improvement in overall score on the “old” SAT, which had a range from 400 to 1600, was no more than about 30 points.

Finally, it is clear that SES is not what accounts for the fact that SAT scores predict success in college. In the University of Minnesota study, the correlation between high school SAT and college GPA was virtually unchanged after the researchers statistically controlled for the influence of SES. If SAT scores were just a proxy for privilege, then putting SES into the mix should have removed, or at least dramatically decreased, the association between the SAT and college performance. But it didn’t. This is more evidence that Boylan overlooks or chooses to ignore.  

What this all means is that the SAT measures something—some stable characteristic of high school students other than their parents’ income—that translates into success in college. And what could that characteristic be? General intelligence. The content of the SAT is practically indistinguishable from that of standardized intelligence tests that social scientists use to study individual differences, and that psychologists and psychiatrists use to determine whether a person is intellectually disabled—and even whether a person should be spared execution in states that have the death penalty. Scores on the SAT correlate very highly with scores on IQ tests—so highly that the Harvard education scholar Howard Gardner, known for his theory of multiple intelligences, once called the SAT and other scholastic measures “thinly disguised” intelligence tests.  

One could of course argue that IQ is also meaningless—and many have. For example, in his bestseller The Social Animal, David Brooks claimed that “once you get past some pretty obvious correlations (smart people make better mathematicians), there is a very loose relationship between IQ and life outcomes.” And in a recent Huffington Post article, psychologists Tracy Alloway and Ross Alloway wrote that

IQ won’t help you in the things that really matter: It won’t help you find happiness, it won’t help you make better decisions, and it won’t help you manage your kids’ homework and the accounts at the same time. It isn’t even that useful at its raison d'être: predicting success.

But this argument is wrong, too. Indeed, we know as well as anything we know in psychology that IQ predicts many different measures of success. Exhibit A is evidence from research on job performance by the University of Iowa industrial psychologist Frank Schmidt and his late colleague John Hunter. Synthesizing evidence from nearly a century of empirical studies, Schmidt and Hunter established that general mental ability—the psychological trait that IQ scores reflect—is the single best predictor of job training success, and that it accounts for differences in job performance even in workers with more than a decade of experience. It’s more predictive than interests, personality, reference checks, and interview performance. Smart people don’t just make better mathematicians, as Brooks observed—they make better managers, clerks, salespeople, service workers, vehicle operators, and soldiers.

IQ predicts other things that matter, too, like income, employment, health, and even longevity. In a 2001 study published in the British Medical Journal, Scottish researchers Lawrence Whalley and Ian Deary identified more than 2,000 people who had taken part in the Scottish Mental Survey of 1932, a nationwide assessment of IQ. Remarkably, people with high IQs at age 11 were more considerably more likely to survive to old age than were people with lower IQs. For example, a person with an IQ of 100 (the average for the general population) was 21 percent more likely to live to age 76 than a person with an IQ of 85. And the relationship between IQ and longevity remains statistically significant even after taking SES into account. Perhaps IQ reflects the mental resources—the reasoning and problem-solving skills—that people can bring to bear on maintaining their health and making wise decisions throughout life. This explanation is supported by evidence that higher-IQ individuals engage in more positive health behaviors, such as deciding to quit smoking.

IQ is of course not the only factor that contributes to differences in outcomes like academic achievement and job performance (and longevity). Psychologists have known for many decades that certain personality traits also have an impact. One is conscientiousness, which reflects a person’s self-control, discipline, and thoroughness. People who are high in conscientiousness delay gratification to get their work done, finish tasks that they start, and are careful in their work, whereas people who are low in conscientiousness are impulsive, undependable, and careless (compare Lisa and Bart Simpson). The University of Pennsylvania psychologist Angela Duckworth has proposed a closely related characteristic that she calls “grit,” which she defines as a person’s “tendency to sustain interest in and effort toward very long-term goals,” like building a career or family.   

Duckworth has argued that such factors may be even more important as predictors of success than IQ. In one study, she and UPenn colleague Martin Seligman found that a measure of self-control collected at the start of eighth grade correlated more than twice as strongly with year-end grades than IQ did. However, the results of meta-analyses, which are more telling than the results of any individual study, indicate that these factors do not have a larger effect than IQ does on measures of academic achievement and job performance. So, while it seems clear that factors like conscientiousness—not to mention social skill, creativity, interest, and motivation—do influence success, they cannot take the place of IQ.

None of this is to say that IQ, whether measured with the SAT or a traditional intelligence test, is an indicator of value or worth. Nobody should be judged, negatively or positively, on the basis of a test score. A test score is a prediction, not a prophecy, and doesn’t say anything specific about what a person will or will not achieve in life. A high IQ doesn’t guarantee success, and a low IQ doesn’t guarantee failure. Furthermore, the fact that IQ is at present a powerful predictor of certain socially relevant outcomes doesn’t mean it always will be. If there were less variability in income—a smaller gap between the rich and the poor—then IQ would have a weaker correlation with income. For the same reason, if everyone received the same quality of health care, there would be a weaker correlation between IQ and health.

But the bottom line is that there are large, measurable differences among people in intellectual ability, and these differences have consequences for people’s lives. Ignoring these facts will only distract us from discovering and implementing wise policies.

Given everything that social scientists have learned about IQ and its broad predictive validity, it is reasonable to make it a factor in decisions such as whom to hire for a particular job or admit to a particular college or university. In fact, disregarding IQ—by admitting students to colleges or hiring people for jobs in which they are very likely to fail—is harmful both to individuals and to society. For example, in occupations where safety is paramount, employers could be incentivized to incorporate measures of cognitive ability into the recruitment process. Above all, the policies of public and private organizations should be based on evidence rather than ideology or wishful thinking.