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NIH Research Matters

May 2, 2011

Motivation May Influence IQ Scores

Intelligence test scores, a new study suggests, may reflect more than intelligence. Scores rise when incentives are offered. And when the stakes are low, student motivation, which varies widely, correlates with test scores and certain successes later in life.

Photo of a hand with a pencil on a test sheet.

Many studies have shown that intelligence quotient (IQ) scores can predict your likely academic achievement, health, lifespan and job performance. The scores are presumed to measure intelligence in test-takers trying to perform their best. But people taking these tests have varying levels of attentiveness and determination. This raises questions about whether the tests are measuring non-intelligence traits as well, such as motivation, competiveness and self-discipline, which can also predict life outcomes.

To take a closer look, Dr. Angela Lee Duckworth of the University of Pennsylvania and her colleagues conducted a 2-pronged study that looked at pre-existing data on IQ scores. Their research was supported by NIH’s National Institute of Mental Health (NIMH) and National Institute on Aging (NIA). Results were published in the April 25, 2011, advance online edition of the Proceedings of the National Academy of Sciences.

In one part of the study, the scientists reviewed 46 previous experiments that examined how financial incentives affect IQ scores. The analysis included data on more than 2,000 test-takers, mostly between the ages of 6 and 18. The scientists found that material rewards, such as money, boosted IQ scores noticeably, by about 2/3 of a standard deviation (SD), or about 10 IQ points. The effect was greatest for people who started out with lower scores. Those with an initial score below 100 showed an increase of nearly 1 SD, or about 15 IQ points.

In the second part of the study, the researchers analyzed data from the Pittsburgh Youth Study, which followed 250 boys from adolescence to early adulthood. The boys were videotaped around age 12 while taking an IQ test. Each student’s level of motivation was rated by 3 trained observers, who reviewed 20 minutes of footage and looked for behaviors that might indicate attentiveness or lack of interest in the test.

The scientists found that the students’ IQ scores accurately predicted later outcomes in life, including academic performance in adolescence, criminal convictions, employment and years of education in early adulthood. However, when the researchers corrected for the influence of test motivation, the predictive power of the IQ scores dropped substantially, especially for non-academic outcomes.

“The predictive power of IQ tests is not just from the intelligence part but also from motivation on test day, which may be based on non-cognitive traits that are also helpful in life,” Duckworth says. When the stakes are low, as in a research setting, some people may be naturally motivated to try harder than others, and this can confound measurement of intelligence.

“When you have an incentive to do well—like if you’re taking an SAT test or if your job depends on it—then you’re probably trying close to maximum while taking the test,” Duckworth adds. “But when there are no stakes for the test-taker, you can’t assume that test motivation is always maximal.”

—by Vicki Contie

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About NIH Research Matters

Editor: Harrison Wein, Ph.D.
Assistant Editors: Vicki Contie, Carol Torgan, Ph.D.

NIH Research Matters is a weekly update of NIH research highlights from the Office of Communications and Public Liaison, Office of the Director, National Institutes of Health.

This page last reviewed on December 4, 2012

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