Alexandra Ossoli in Tonic:
What has become clearer in recent years, is that intelligence, like many facets of health and even complex diseases, is the result of a complex interaction of genetics and the environment. Several studies over the past five years have identified hundreds of genes that may be involved in intelligence. The results of IQ tests can even vary depending on a person's state of development, which is usually triggered by genetics—the greatest fluctuation usually happens during adolescence, when the brain is still developing. But non-genetic factors can drastically affect IQ. There are elements of a person's childhood environment that can depress IQ scores later in life, such as poverty, poor at-home intellectual environment, and exposure to toxic chemicals such as lead. Repeated head injuries lower IQ in the long run. Some things can also raise them, such as hanging out with smarter people—moving a child from an impoverished household to a middle- or upper-class one can result in sizable gains in IQ scores. "The brain seems to be rather like a muscle—the more you use it, the stronger it gets. That means you can upgrade your own intelligence all through life," intelligence researcher James Flynn told The Australian. For an individual, it's easier to depress the score of IQ tests over a lifetime than to boost them, especially after adolescence. "You don't see many reports of significant increases in IQ unless someone had screwed up the testing," Silverman says.
Over the course of generations, however, people have in fact performed better on IQ tests, a phenomenon called the Flynn Effect. Some of the drivers of this trend include more education, less exposure to toxins, and the fact that more people work in cognitively demanding jobs, Flynn said in a 2013 TED talk. Whether these changes in IQ scores document a change in actual intelligence is still a matter of debate, Nisbett says. And for most people who take IQ tests just for fun, the results probably don't really matter. Those scores do matter if the test is being used to assess someone for a cognitive disability. "There, IQ testing is pretty good at doing what it's supposed to do, which is to identify people with a significant cognitive impairment that is unlikely to change in the foreseeable future," Silverman says. Scores really matter in these cases, because variation between tests can make the difference between whether or not someone with an intellectual disability receives government benefits or not.
And though certainly intelligence helps people succeed in their careers, it's not necessarily the most important factor. As Warren Buffett famously said, "If you are in the investment business and have an IQ of 150, sell 30 points to someone else."
More here.
