Can IQ tests and grades predict life outcomes?

The better we understand what tests are actually measuring, the more useful they’ll be
Alberto G., flickr.com, CC BY 2.0
Alberto G., flickr.com, CC BY 2.0

Tests are a big part of the U.S. education system. Standardized tests are given to students at the end of each grade. Tests are required to get into college, law school, graduate school, and medical school. Test scores qualify or disqualify students for major scholarships. And along with achievement tests, many students will take an IQ test at some point during their academic career.

According to John Eric Humphries, a Ph.D. candidate in the Department of Economics at the University of Chicago, these types of tests really became popular in the 1940s. “The idea of modern tests and the way we think about them today really rose to prominence during World War II,” he says. During that time, testing soldiers entering the military began to take hold and the national achievement test, the SAT, while having been around since the 1920s, saw a dramatic increase in test-takers. Now, the SAT is one of the two major tests, along with the ACT, required with college applications.

But while testing is deeply embedded in the academic culture, what is it really measuring? Do IQ scores and grade point averages predict how well a student will score on tests like the SAT? Do any of these measures correlate with life outcomes? Humphries and his colleagues wanted to know.

What are tests testing?

In a new study published in PNAS, the researchers examined data collected from students in the U.S., the Netherlands, and the U.K. This included IQ scores, achievement test scores, grades, and adult outcomes. It also included personality measures, which covered elements like conscientiousness, neuroticism, and openness to experience and were used to try to capture relevant aspects beyond IQ. “We think there are other aspects of an individual that matter in life beyond IQ,” says Humphries, “and one of those aspects is personality.”

Taking all of these factors into account and looking at how they relate to each other, some interesting patterns emerged. IQ scores were comparatively better than personality or grades at predicting scores on achievement tests. But when it came to grades, personality was a better predictor. And with life outcomes like wages, number of arrests, and life satisfaction, the study found that grades, achievement test scores, and personality were all better predictors than were IQ scores.

“Grades aren’t just your ability to pass the exam,” says Humphries, “they are your ability to show up to class, your ability to do your homework, and your ability to participate well with others.”

So, while IQ tests do capture something, they’re not the only factors that contribute to academic or life success. Non-cognitive measures, like personality, are important too.

“A key point here is that measures of grade point averages, which are not purely test-based and in many cases, not even mostly test-based, are providing important measures of future success,” says Humphries. And he points out that this is because grades are an accumulation of factors that include both personality and cognitive ability. Both of which influence future success. “Grades aren’t just your ability to pass the exam,” says Humphries, “they are your ability to show up to class, your ability to do your homework, and your ability to participate well with others.”

And ultimately, the better we understand what IQ and achievement tests are actually measuring, the more useful they’ll be in student, teacher, and school assessments.