Many believe that IQ, or intelligence quotient, is an antiquated measurement of little real-world use, but researchers say IQ is a reliable predictor of health, prosperity, and longevity.
"Today there's an endless supply of psychological books and TED talks that are dismissive of IQ, or argue that it can be supplanted," Brian Resnick writes for Vox. But he disagrees, citing IQ researcher Stuart Ritchie.
Resnick argues, "IQ doesn't necessarily set the limit for what we can do, but it does give us a starting point."
What is IQ?
First, it's important to understand how IQ works. IQ is determined by combining scores for tests of reasoning, mental processing speed, acquired knowledge, and memory.
"The classic finding— I would say it is the most replicated finding in psychology—is that people who are good at one type of mental task tend to be good at them all," Ritchie explains.
The average IQ score is, by definition, 100. Most people fall within one standard deviation of the IQ bell curve:
- 68.2 percent of people have average IQs (85–114);
- 13.6 percent have above average IQs (115–129); and
- 2.2 percent have exceptional intelligence (over 130).
IQ and health
Research suggests that people with higher IQs tend to live longer, healthier lives.
The explanation may come down to money: Those with higher IQs tend to earn more, and wealth is correlated with greater access to quality health care and nutrition.
Even so, that increased health doesn't always translate to increased happiness. While there is a positive correlation between IQ and happiness, it's small, Ritchie says, and isn't always statistically significant.
Your IQ is probably fairly fixed
Genetics are responsible for about half of your IQ, Ritchie says, citing studies on twins. But, he adds, genetics don't "seal your destiny." Access to health care, nutrition, and education play a role in your IQ's development—but these environmental factors are harder to pin down than genetics.
"People's lives are really messy, and the environments they are in are messy," Ritchie says. "There's a possibility that a lot of the environmental effect on a person's intelligence is random."
Regardless of genetics and environment, Ritchie says you're likely to stay in the same IQ range throughout your life, whether that's below average, average, or above average. One study found that the IQ scores for a group of 90-year-olds were similar to the same group's scores on tests taken when they were age 11.
But even though IQ changes only modestly throughout your life, research suggests it peaks in your mid-20s. After those years, your mental quickness and ability to solve new problems begin to decline.
But average IQs are on the rise
Research suggests that average IQ scores are rising about two to three points per decade, likely due to increased access to nutrition, health care, and education. The increase also may be linked to an increased societal emphasis on abstract thinking.
Developing countries are making greater strides in mean IQ than others. As quality of nutrition and health care continue to improve in those countries, so do IQ rates (Resnick, Vox, 5/24; Resnick, Vox, 5/25).