Brain Rules for Baby (John Medina) / quote 25 of 91
IQ is a dress size, not a birth date
Like Kirstie’s dress size, IQ is malleable. IQ has been shown to vary over one’s life span, and it is surprisingly vulnerable to environmental influences. It can change if one is stressed, old, or living in a different culture from the testing majority. A child’s IQ is influenced by his or her family, too. Growing up in the same household tends to increase IQ similarities between siblings, for example. Poor people tend to have significantly lower IQs than rich people. And if you earn below a certain income level, economic factors will have a much greater influence on your child’s IQ than if your child is middle class. A child born in poverty but adopted into a middle-class family will on average gain 12 to 18 points in IQ. There are people who don’t want to believe IQ is so malleable. They think numbers like IQ and “g” are permanent, like a date of birth instead of a dress size. The media often cast our intellectual prowess in such permanent terms, and our own experience seems to agree. Some people are born smart, like Theodore Roosevelt, and some people are not. The assumption is reassuringly simplistic. But intelligence isn’t simple, and neither is our ability to measure it.