Where does the process of introspection — the ability to think about our own thoughts, behavior, and feelings — take place in the physical brain? The center for this action has, until now, been unidentified.
In a new study, however, researchers at the Institute of Cognitive Neuroscience and the Wellcome Trust Centre for Neuroimaging at UCL (University College London) have found an area of the brain that is bigger in people who are better at introspection, signifying that this area might be associated with thinking about our own thoughts.
“We introspect when we think about our own thoughts, feelings or the decisions we have made,” says Steve Fleming, joint first author of the study.
“It’s something we do all the time, but some people are better at it than others. Even if we don’t get feedback when we make a choice, we often know intuitively if it’s a good or a bad decision.”
Measuring a person’s introspection abilities has always been a challenge for scientists. Unlike learning a task, where achievement is visible, or decision-making, where we can observe if a person’s choice is correct or not, there are no outward indicators for introspective thought.
So the researchers, headed by Wellcome Trust Senior Fellow Professor Geraint Rees from UCL, developed a test that would provide both an objective measure of each participant’s task skills and also a measure of how well they thought they did – in other words, how good they were at introspection.
Thirty-two volunteers were each shown two screens, with each screen containing six patches; on one of the screens, one patch was brighter than the others. The volunteers were asked to identify which screen contained the brightest patch, and then asked to rate how confident they were in their choice before being told the correct answer.
“We made this task difficult so that people could never be entirely sure about whether their answer was correct,” explains Dr. Rimona Weil, joint first author on the paper. “Someone who is good at introspection will be confident when they know they are correct, because they have seen it clearly. But they will be less confident when they are not sure whether they are right or wrong.”
“It’s like ‘Who Wants to be a Millionaire?’ A good contestant will go with their answer when they’re sure, and phone a friend if unsure. But a poor contestant might not be as good at judging how likely they are to be correct.”
Even though the participants performed equally well on the test, there was a significant difference in introspective ability between individuals. The scientists then observed the structure of the participants’ brains using scans taken with a magnetic resonance imaging (MRI) scanner, searching for parts of the brain that correlated with introspective ability.
“We found a correlation between introspective ability and the structure of a small area of prefrontal cortex near the front of the brain,” explains Professor Rees. “The better a person was at introspection, the more grey matter they had in this area. The same was true for the white matter or nerve connections in this area.
“At this stage, we don’t know why their grey or white matter differs in this small area. Does this area develop as we get better at reflecting on our thoughts, or are people better at introspection if their prefrontal cortex is more developed in the first place?”
Scientists hope the results of this study will help them understand why and how brain damage affects a person’s ability to reflect on their own thoughts, and to develop better treatments.
“Take the example of two patients with mental illness, one who is aware of their illness, and one who is not,” says Fleming. “The first person is likely to take their medication, the second less likely. If we understand self-awareness at the neurological level, then perhaps we can adapt treatments and develop training strategies for these patients.”
This study is published in the journal Science.