People who seem particularly introspective tend to have a part of their brain that is larger, researchers have found.

Introspective people know their minds better than others — for example, in being confident that they made the right decision.

Research reported Friday is a step toward understanding the biology behind that important part of human consciousness. It's work necessary for one day tackling brain injuries or diseases that rob people of key aspects of self-reflection — such as schizophrenia patients who aren't aware that they're ill and thus don't take their medication.

Introspection is basically thinking about your thinking, a way to judge your own thoughts and actions — and inherently difficult to study.

By learning the neurological basis of self-awareness, "might we be able to come up with potential strategies to intervene in these cases and improve people's introspective ability?" asks Stephen Fleming of University College London, lead author of the new research published in the journal Science.

The British research team devised a way to measure introspective ability by comparing people's confidence in a decision they made with the accuracy of that decision.

Here's how it worked: Researchers briefly showed 32 healthy people computer screens containing patterns, one slightly brighter than the rest, similar to tests used in eye exams. First, the volunteers had to rapidly choose which screen contained the brighter pattern.

Because some people are simply better observers, the computer adjusted the level of difficulty to each individual so that the task was equally hard for everyone and no one could be completely sure their answer was correct.

Then the volunteers had to rate how confident they were in their answer.

The idea was that people with good introspective abilities would be more confident when they were right, and more likely to second-guess themselves when they really were wrong. People who are just brash and overconfident might lead an outsider to think they were right, but in reality wouldn't show that correlation.

Focus on grey matter

Brain scans showed people's introspective ability was strongly linked to the amount of grey matter in a spot of the prefrontal cortex, right behind the eyes, the researchers reported.

In addition, the study found people who were more introspective also had stronger functioning white matter in that part of the brain — the nerve fibres that act as a telephone system to allow cells to communicate with others.

Bolstering the findings, previous studies show schizophrenia is associated with poor prefrontal cortex functioning, and that strokes in that area can rob people of introspective ability, Fleming said.

Much more research is needed, however, to address the which-came-first question: are these brain differences innate? Or do they reflect this brain region getting stronger as people try to spend more time monitoring their own mental state, meaning it's an ability that might be improved with training?

Regardless, much brain research to date has focused on simpler questions, like how memory is formed. The new findings help shed light on more sophisticated, higher-level abilities, said Columbia University psychology researcher Hakwan Lau, who wasn't involved in the research but analyzed it in an accompanying article in Science.

"Understanding how the brain works is important in its own right," said Lau.