A new study has found that in people who are good at turning their thoughts inward and reflecting upon their decisions, the size of a specific region of the brain is larger than those who do not.
This act of introspection-or "thinking about your thinking"-is a key aspect of human consciousness, though scientists have noted plenty of variation in peoples' abilities to introspect.
Based on the findings, the researchers, led by Prof. Geraint Rees from University College London, suggests that the volume of gray matter in the anterior prefrontal cortex of the brain, which lies right behind our eyes, is a strong indicator of a person's introspective ability.
In addition, they say the structure of white matter connected to this area is also linked to this process of introspection.
It remains unclear, however, how this relationship between introspection and the two different types of brain matter really works.
The findings establish a correlation between the structure of gray and white matter in the prefrontal cortex and the various levels of introspection that individuals may experience.
In the future, the discovery may help scientists understand how certain brain injuries affect an individual's ability to reflect upon their own thoughts and actions.
With such an understanding, it may eventually be possible to tailor appropriate treatments to patients, such as stroke victims or those with serious brain trauma, who may not even understand their own conditions.
"Take the example of two patients with mental illness-one who is aware of their illness and one who is not. The first person is likely to take their medication, but the second is less likely. If we understand self-awareness at the neurological level, then perhaps we can also adapt treatments and develop training strategies for these patients," said one of the study's authors, Stephen Fleming from University College London.
"We want to know why we are aware of some mental processes while others proceed in the absence of consciousness. There may be different levels of consciousness, ranging from simply having an experience, to reflecting upon that experience. Introspection is on the higher end of this spectrum-by measuring this process and relating it to the brain we hope to gain insight into the biology of conscious thought," said Fleming.
The new study will be published in the journal Science.