“If there’s no gas in your car you’re not going to go anywhere. If road conditions are bad, you’re not going to go anywhere,” he said. In the case of intelligence, you need good health, hard work and motivation to take advantage of inherent brainpower.
Another complication is that intelligence comes in many forms. One category is crystallized intelligence, Engle said, which measures how much knowledge a person has acquired and that is highly correlated to education level.
On the flip side is fluid intelligence, which is the ability to reason and solve new problems. Studies of twins show that fluid intelligence is largely genetic. Identical twins are much more similar to each other on measures of fluid intelligence than fraternal twins are.
But, according to recent research, that is true only for people with high socioeconomic status, at least in the United States, where access to education varies by zip code. In other words, genes only kick in to influence IQ when people are already getting a relatively good education.
As scientists learn more about the components of intelligence, they are developing new ways to assess nuances in the way people think.
Traditional IQ tests have long focused on math and verbal skills, Lubinksi said. Now, though, it’s becoming clear that the ability to think spatially and rotate shapes in the mind’s eye is essential for pilots, orthopedic surgeons, architects and other occupations. Some newer tests evaluate those visualization skills.
Even as testing gets more refined, debates continue about whether IQ tests should be used at all. The military has used intelligence testing as a way to place people in the toughest posts, and experts said that evaluations can be useful in professional and educational settings, too -- as long as they’re used responsibly and sensitively.
For kids who are struggling in school, for instance, IQ tests can help determine whether they’re so intelligent that they’re bored or if they have cognitive deficits that require special attention. Determining mental strengths and weaknesses can also help teachers tailor education and steer students towards jobs that best fit their skills.
On the other hand, experts said, it wouldn’t be a good idea to test every child’s IQ and announce the number because that would unnecessarily and unfairly shape expectations.
“It’s like every other tool,” Lubinski said. “It can cause harm, and it can be of great service. There are examples of both.”
As for MacArthur fellows, IQ tests have nothing to do with who wins and “genius” is probably not the right word, Engle said.
“I know two MacArthur award winners,” he said. “They’re pretty normal people who have done some interesting things.”