What Does IQ Really Measure?
April 25, 2011
in his 2009 book “Intelligence and How to Get It,” Richard Nisbett, a psychologist at the University of Michigan, Ann Arbor, argued that differences in IQ scores largely disappear when researchers control for social and economic factors.
Nisbett agrees that the study is “tremendously important in its implications.”
Motivation, along with self-discipline, “are crucial,” Nisbett says.
“A high IQ and a subway token will only get you into town.”
Lex Borghans, an economist at the Maastricht University in the Netherlands, who has also studied the relationship between intelligence tests and economic success, says the new report shows that “both intelligence and personality matter.”
Even if native intelligence cannot be increased, Borghans says, “there might be other routes to success.”
this article is based on the original paper:
Role of test motivation in intelligence testing
Angela Lee Duckworth, et al.
Proc Natl Acad Sci U S A. 2011 May 10;108(19):7716-20.
Intelligence tests are widely assumed to measure maximal intellectual performance, and predictive associations between intelligence quotient (IQ) scores and later-life outcomes are typically interpreted as unbiased estimates of the effect of intellectual ability on academic, professional, and social life outcomes.
The current investigation critically examines these assumptions and finds evidence against both.
First, we examined whether motivation is less than maximal on intelligence tests administered in the context of low-stakes research situations.
Specifically, we completed a meta-analysis of random-assignment experiments testing the effects of material incentives on intelligence-test performance on a collective 2,008 participants.
Incentives increased IQ scores by an average of 0.64 SD, with larger effects for individuals with lower baseline IQ scores.
Second, we tested whether individual differences in motivation during IQ testing can spuriously inflate the predictive validity of intelligence for life outcomes.
Trained observers rated test motivation among 251 adolescent boys completing intelligence tests using a 15-min “thin-slice” video sample.
IQ score predicted life outcomes, including academic performance in adolescence and criminal convictions, employment, and years of education in early adulthood.
After adjusting for the influence of test motivation, however, the predictive validity of intelligence for life outcomes was significantly diminished, particularly for nonacademic outcomes.
Collectively, our findings suggest that, under low-stakes research conditions, some individuals try harder than others, and, in this context, test motivation can act as a third-variable confound that inflates estimates of the predictive validity of intelligence for life outcomes.
a quality journalistic analysis: