We’ve all seen the pretty pictures. Colored scans, produced by techniques that measure blood flow or the movement of a tracer chemical, reveal the activity of areas of the brain when we are thinking about something. The revolution in imaging in the past couple of decades has taught us a lot about what the brain is doing while we cogitate. One thing we’ve learned is that those more active areas aren’t always the same from brain to brain when considering a certain problem. Not all brains are the same size or shape, as you might expect, but they also think differently.

So where does intelligence arise? Neuroscientist Richard J. Haier poses that question in our cover story, “What Does a Smart Brain Look Like?” Just as occurs with other types of processing, how we think when we are solving tasks differs among individuals. “Two people with the same IQ may solve a problem with equal speed and accuracy, each using a very different network of brain areas,” Haier writes. It may be time for a new definition of intelligence, he proposes, based on the size of key brain areas and how efficiently they manage information flow. Could brain scans someday show our aptitude for a given subject, helping us figure out what topics to focus on for our best success?

Intelligence not only exists in various places in the brain, it’s variable as well. We all know people who seem perfectly smart and yet have made poor decisions at critical junctures. As it turns out, there’s a reason for that: it is possible to test high in IQ yet to suffer from a logical-thought defect known as dysrationalia. In “Rational and Irrational Thought: The Thinking That IQ Tests Miss,” neuroscientist Keith E. Stanovich provides two causes. One is that people are often cognitive misers—taking the easy way out when trying to solve problems, which leads them to make errors. Second, they may lack the specific knowledge, rules or strategies to handle a situation. Stanovich argues that tests that can measure dysrationalia should be conducted more often to identify the flaw, the better to manage it. Sounds smart to us.