How Do We Measure Intelligence?

Is Intelligence Fixed or Variable?

We can all agree that humans (using their brains, one hopes) change the world; now we're going to say, our brains change, and here's how we change our brains—and that means intelligence, too. Yet countless studies attest to IQ as inborn—all nature—and others say it's mostly all nurture. Some say IQ is fixed and that's what makes it reliable. These viewpoints differ because each is using a different definition for intelligence. Here's how they line up:

It's easy to see that the traditional models (g and IQ) consider intelligence to be fixed, and the newer, less traditional ones consider it more mutable. Although many cultures believe that the primary determinant of success in life is effort, the prevailing American view is that talent means more than hard work.

This makes the traditional fixed view of IQ measurement appealing here. So if the tested IQ of a child is 85 but rises to 100 as the child becomes a teenager (because of whatever improvement in the child's circumstances), the fixed-IQ advocates would claim that the real IQ was 100, and the 85 score was a suppressed IQ based on abuse, neglect, or impoverished conditions.

In other words, the fixed-IQ advocates argue that everyone has a set IQ, and all the enhancement and enrichment in the world will only bring someone up to their personal genetic capacity—which is not necessarily to be a star performer, honor roll student, or Mensa member. With the cards you've been dealt at birth, what you can do with your intelligence is accept it. The claim says that if you get a healthy upbringing, your IQ will be stable and it won't change regardless of any efforts to create enrichment. Could intelligence really have a settling point in each of us? And how high is that point? No one is sure, but it's worth exploring. Visionary scientist Ray Kurzweil says that we may be able to raise intelligence dramatically with artificial means, including nanotechnology. His book The Singularity Is Near studies many new exciting and frightening options that are based on brand-new technologies.⁴⁵ The human engineering side may be fraught with political, social, economic, and ethical considerations. But on a more practical level, in Outsmarting IQ, Harvard professor David Perkins has elegantly shown how IQ is not fixed.⁴⁶

The best way to convey this idea is that the greater the existing level of intelligence, the less that can be done for it. The lower the baseline of intelligence, the greater the capacity for positive change. This eliminates the "either or" or "black and white" thinking. In addition, we might think of intelligence as having breadth (lateral in scope) or depth (more specialized in one area, like IQ). In short, there is always room to grow.