A new study reveals that ‘introspection’ (thinking about our own thoughts or behavior) is anchored in a specific part of our brain.

The research by scientists from the Institute of Cognitive Neuroscience and the Wellcome Trust Centre for Neuroimaging at University College London examined people’s accuracy when reflecting on decisions they had made.

"We were not studying the tendency to think too much, or the tendency to introspect, we were studying the accuracy of that process when it does occur.  We don’t have any data on the people who come into our study," says Steve Fleming, joint first author of the study,  such as how much they engage in introspection. "We just know that when we actually ask them to do our task, some people are more accurate at reflecting on their own decisions than others."

Then the team linked this to brain structure.

They arranged the experiment so that while all the participants had a similar accuracy in judging the comparative brightness of patches on a computer screen, what differed was the ability to reflect accurately on the correctness of their response.

"After every decision," explains Fleming, "and they made hundreds of these simple visual decisions, we asked them to rate their confidence that they had got that decision correct. That was the key measure of introspective ability, we could then say that people who were good at introspection will try to use high confidence ratings when they actually were correct, and low confidence ratings when they weren’t correct, even without getting any feedback on their decisions."

When the test was completed, the participants underwent magnetic resonance imaging (MRI) scans, giving the researchers an image of the grey matter in the brain which contains cells and the white matter which is the connection between the cells, and it showed that those better at introspection had more grey matter in the prefrontal cortex near the front of the brain.

 "There is still more evidence to be gained here," says Fleming, "we are just looking at a snapshot of the structure of the brain, but what we really want to know is why does the structure there play a role in introspection?"

In order to get closer to an answer, a next step is to measure introspection in real time.