MONDAY, April 25 (HealthDay News) -- A new study suggests that the ability of IQ tests to predict your future -- in areas such as job success, education and any brushes with the law -- has a lot to do with how motivated you are when you take the test.

In other words, an IQ test may provide good insight into a test-taker's life, "but it might not predict it for the reason you think," explained study author Angela Lee Duckworth, an assistant professor at the University of Pennsylvania.

Intelligence quotient (IQ) tests are valued in part because researchers have linked scores to success or failure later in life. "It predicts how long you'll live, whether you'll stay married, your grade point average," Duckworth noted.

On top of that, IQ tests seem to measure not only intelligence but the ability to become smarter.

"Social scientists think they're accurate measures of how well people can learn: this kid's got a 120, so they can learn really well," Duckworth said. "This kid's got an IQ of 95, so they can't learn that well."

But not everyone who takes an IQ test gives it their full attention. "I do a lot of work in urban classrooms, and it was salient to me that some of these kids did not care," Duckworth explained. "They put their pencils and heads down after one or two questions. It was obvious that they were not trying to do it. They hadn't even started trying."

Duckworth said that she and her colleagues "wanted to know how much of the test's predictive power is measuring what it should be measuring, and how it much of it is from your actual motivation."

They first reviewed previous studies, and found that giving incentives to test-takers to do a good job boosted scores.

In addition, the authors analyzed data from a long-term study that followed 250 teenage boys from Pittsburgh into adulthood. They were videotaped while taking an IQ test, and researchers gauged how motivated they appeared.

When they adjusted their statistics to take away the influence of motivation upon the results, the researchers found that the IQ tests did a poorer job of predicting what would happen to the boys later in life.

It's possible that some of the things that make someone motivated -- compliance, a natural interest in solving problems, competitiveness -- are high in those who do well on the tests and may help them do better in life, Duckworth said.

However, the findings "don't say these IQ scores are all about motivation," Duckworth said. "It's not saying anyone can get 140 if they try hard enough."

Robert Sternberg, a psychology professor and provost at Oklahoma State University, praised the study but added that the findings aren't exactly shocking. "To almost anyone except some subset of those psychologists who study IQ testing, it will come as little surprise that motivation is an extremely powerful determinant of performance in school and in life," he said.

The study is published in this week's Proceedings of the National Academy of Sciences.

More information

For more about IQ, visit the U.S. National Library of Medicine.