Never underestimate personality. A sense of humor will make you popular; a little confidence will win you jobs; and the right amount of sass or cockiness will score you dates. Personality shines from within, mingling spirit and intelligence, so it’s safe to assume it originates in the brain.

While they would have to agree, neuroscientists naturally add a few lines, a little shading, and some general complexity to this picture of personality’s genesis. Take, for instance, the Yale researchers who recently created a brain activity matrix for 126 people based on MRI data. To do this, they looked at 268 distinct brain regions and measured how strongly the activity of each region compared to the activity in every other region. Creating a matrix for each person, they soon discovered everyone had his or her own unique matrix, quite like we all have a unique fingerprint.

Next, to test their discovery, the team worked backwards: they searched through MRI scans from previous sessions to see if they could identify each person based on the matrix created. In fact, the researchers could pinpoint each participant with surprising accuracy.

Even though the stream of consciousness flowing through our brains is always moving, then, people always looked most similar to themselves, explained Emily Finn, the lead author of the study.

However, the type of scans had bearing on their accuracy. The scans taken while participants performed simple motor tasks made their identity search more difficult, causing their accuracy rates to plummet below 70 percent. Yet, their accuracy rate shot up to 99 percent when they looked at scans taken while participants were simply resting, essentially doing nothing other than daydreaming.

Dr. Todd Constable, senior author of the study, explained that when two people were confused among the pile of scans, it wasn’t when they were trying to find a twin. Each of the twins who participated in the study had a unique matrix.

Examining the data, the researchers found the most distinctive area of the brain for each participant was the frontoparietal network, essentially the high traffic communication lines between the parietal and frontal lobes of the brain. (Your brain is divided into four lobes: frontal, parietal, occipital, and temporal.) “Evolutionarily that’s the last thing that developed and made humans unique from other animals,” Constable told Medical Daily.

It is also the area of the brain that defines your personality.

“Your personality is really unique so maybe that’s reflected in these functional connections in those areas on [the frontal lobes],” said Constable. “We thought that made sense.”

Another study based on the Big Five personality traits supports this idea, though from another perspective.

Personality Continuum

As personality psychologists see it, the Big Five traits are openness, conscientiousness, extraversion, agreeableness, and neuroticism (OCEAN). According to the Big Five theory, each of us as lands somewhere along the continuum stretching between five sets of opposing qualities: extraversion and introversion; emotional stability and neuroticism; conscientiousness and impulsivity; agreeableness and hostility; and openmindedness and closemindedness. Naturally, each of these traits contains sub-characteristics.

Openness, for example, includes adventurousness, imagination, curiosity, and emotionality, while extroversion comprises personal energy and the tendency to seek stimulation. Conscientiousness merges with self-discipline, dutifulness, and an orientation toward achievement, while agreeableness involves compassion. Finally, neuroticism contains the seeds of anxiety, anger, and depression.

So, to understand how brain region size might relate to personality, psychologists at the University of Minnesota worked with 116 participants. After answering a personality questionnaire, the participants underwent a brain imaging test. Turns out, their findings provide support for a theory that neurobiological systems underlie the Big Five.

They discovered all the extroverted participants had significantly larger medial orbitofrontal cortex, located on the frontal lobe above and behind the eyes. The conscientious ones had a bigger lateral prefrontal cortex; this part of our brain gets involved when we set a goal for ourselves or obey rules. The brains of the neurotics in the group showed smaller volumes in dorsomedial prefrontal cortex among other characteristics. Overall, the brain regions impacted are those responsible for negative emotions in the neurotics.

In fact, the regions affected in people scoring high on the neurotic scale “may reflect higher sensitivity both to the possibility of error and to pain following punishment,” wrote the authors. By comparison, those scoring high in agreeableness had larger brain regions that enable empathy and understanding of others’ emotions and thoughts. Unusually, the researchers did not find any brain regions specifically corresponding to openness.

Though both studies are too small to be conclusive, the results of each are still intriguing. Our personalities may be reflected in both the relative size of our brain regions and the connections they most often make.