Can Intelligence Really Be Measured?


Every year, the MacArthur Foundation bestows large financial grants on a group of people who are doing exceptionally creative or important work.

MacArthur fellowships are often called “genius grants,” and grant-winners tend to be unusually motivated, passionate and forward thinking. But are they geniuses? The annual conversation that ensues raises questions about what it means to be intelligent and whether that’s something that can be cultivated, measured or even defined.

Despite decades of research into how different brains work, experts said, there are no easy answers. Scientists now know that there are multiple types of intelligence. There's a strong genetic component to certain aspects of intelligence. And scores on intelligence tests are tightly linked to school performance, future income level, health and more.

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But IQ scores are far from the only factor that determines how well people do in life. Also, conversations about innate differences in intelligence continue to make people uneasy, probably because there is a long history of racism, classism, sexism and even religious discrimination tied up in discussions about who is smarter than whom.

“The field is just fraught with controversy after controversy,” said Randall Engle, a psychologist at the Georgia Institute of Technology in Atlanta. “There are group differences all over the place in intelligence measures and that just adds to the controversy. It’s hard for the field to come to grips with what’s understandable about this in the midst of all this craziness.”

Researchers have been interested in understanding the nature of intelligence since at least the 1800s, but early studies were hampered by complications.

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Part of the problem was that intelligence tests were designed before anyone had come up with a specific definition of what they were trying to measure, Engle said. What’s more, British scientist Sir Francis Galton, who was the first to use statistics to test whether intelligence could be inherited, was also a eugenicist, and beliefs that good traits were inborn led to forced sterilizations and other terrible outcomes.

In the early 1900s, French psychologist Alfred Binet developed a test to identify children who might need extra help in school, and his work was incorporated into the Stanford-Binet Intelligence Scales, which originally focused on verbal skills. That and other modern IQ tests have changed over the years as new research changes our understanding of what intelligence is.

Generally, Engle said, different IQ tests correlate well with each other and scores tend to be linked to real-world outcomes. Compared to people who score lower on the tests, for example, people with the highest IQs file more patents, publish more academic papers, and earn higher incomes.

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But scoring well on an IQ test doesn’t predict success, nor does a relatively average or lower score predict a life of misery.

That’s because having a high IQ is like owning a car with a big engine, said David Lubinksi, psychologist and co-director of the Study of Mathematically Precocious Youth at Vanderbilt University in Nashville, Tenn.

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