Motivation plays a critical role in determining IQ test scores

Angela Lee Duckworth, an assistant professor of psychology in Penn's School of Arts and Sciences, led the research, which involved two related studies.

The first was a meta-analysis of previous research into the effect of incentives on IQ scores. For individuals who had above-average scores at baseline, motivation accounted for only about a quarter of a standard deviation, or about four points. But, for those who had below-average scores, motivation made up almost a whole standard deviation.

The second study involved an experiment in which researchers observed video footage of adolescent boys taking a standard IQ test to rate their motivation and then measured how well they fared in terms of criminal record, job status and educational attainment more than a decade later.

Coders, who were not aware of subjects' IQ scores or the hypothesis of the study, rated each subject's motivation based on a standard rubric of behaviors, such as refusing to answer questions or obviously rushing through the test to make it end as quickly as possible. Ratings of test motivation and IQ scores were about equally predictive of the adult outcomes of years of education, employment status and criminal record.

"What we were really interested in finding out was when you statically control for motivation, what happens to the predictive power of the IQ tests? What we found is that the predictive power goes down significantly," Duckworth said.

Duckworth's research was published April 26 in the journal Proceedings of the National Academy of Sciences.

"When people use IQ tests in social science research, where thousands of kids are taking IQ tests where it doesn't matter to them what they get, what's the effect of motivation on those scores?" Duckworth said.

"IQ scores are absolutely predictive of long-term outcomes. But what our study questions is whether that's entirely because smarter people do better in life than other people or whether part of the predictive power coming from test motivation" Duckworth said.

"Could it be that part of the reason doing well on this test predicts future success is because the kinds of traits that would result in you doing well -- compliance with authority, self-control, attentiveness, competitiveness -- are traits that also help you in life?

"This means that for people who get high IQ scores, they probably try hard and are intelligent," she said. "But for people who get low scores, it can be an absence of either or both of those traits."

The research was conducted by Duckworth; Patrick D. Quinn of the Department of Psychology, University of Texas at Austin; Donald R. Lynam of the Department of Psychological Sciences, Purdue University; and Rolf Loeber and Magda Stouthamer-Loeber of the Department of Psychiatry, University of Pittsburgh School of Medicine.

The research was supported by the National Institute of Mental Health and National Institute on Aging.