A specific area of the brain, located near the front of your head in the prefrontal cortex, is responsible for introspection. People with with more microstructures in this region are better at "metacognition," and possibly better decision-makers too.
In a paper published this week in Science, neuroscientist Stephen Fleming and a team of UK researchers explain that they asked test subjects to engage in a metacognitive exercise while their brains were being scanned. Thoughts qualify as metacognitive if they are thoughts about other thoughts, rather than responses to outside stimuli. In the case of this test, the researchers used a commonly-accepted introspection test. Subjects were asked to do a visual perception test (identifying and rotating objects), and then asked to evaluate whether they performed well on the visual test. The self-evaluation part is what qualifies as metacognitive: You're analyzing your own analysis of something from the outside world.
Fleming and colleagues found that people with more gray and white matter microstructures in a particular area of the prefrontal cortex tended to be more introspective, which is to say, better at evaluating their own performance on the visual test. People who are more introspective in this way tend to be better decision-makers. Their confidence levels tend to match the accuracy of their perceptions..
Does that mean a brain scan could reveal whether you're a good decision-maker?
Hakwan Lau, a Columbia psychology researcher not affiliated with the study, told io9 that more research needs to be done. The region of introspection in the brain hasn't been "isolated," he says, though he thinks it's likely the prefrontal cortex is involved in metacognition. However, he cautions, "those regions are certainly responsible for many other sensory functions." So activity in that region might not just be a result of metacognition.
The good news for people who want to heighten their powers of metacognition is that Fleming and his co-authors say it's possible people could "train" themselves to be better at it. The neurons in your brain are constantly changing and growing, so it would be very possible for somebody to do mental exercises that would beef up connections in the introspection area. Lau agrees that this idea of training "seems plausible - but someone needs to actually demonstrate it."
I'm just hoping that my introspection powers are growing every time I evaluate whether I'm right about how awesome the show Supernatural is going to be when it premieres next week.