The Anatomy of Who We Are
A new study explores the ties between personality and dimensions of the brain.
Posted Feb 13, 2017
By Kirsi Goldynia
The modern quest to identify the physical underpinnings of personality stems in part from the iconic case of Phineas Gage, who in 1848 was impaled straight through the front of the brain with an iron rod—and transformed, it was reported, into a different, less inhibited person. However unfortunate for Mr. Gage, his accident provided a key case study for understanding how the tangible brain and the intangible persona are intertwined.
Since Gage’s time, personality has been studied, analyzed, and broken down every which way in search of a theory to help us understand the foundations of what makes us who we are. For the past few decades, the Five Factor Model of personality has been widely accepted by psychologists as the most accurate of these theories. Its framework deconstructs personality into five essential traits, the so-called Big Five: extraversion, agreeableness, conscientiousness, neuroticism, and openness to experience.
A recent study published in Social Cognitive and Affective Neuroscience found new evidence of a neural infrastructure for these five traits. Through the analysis of this infrastructure, it may eventually be possible to predict personality types and even personality disorders.
Roberta Riccelli at the Magna Græcia University of Catanzaro in Italy worked with an international team of researchers to detect correlates of personality in the cerebrum's outer layer, the cerebral cortex. Using data available through The Human Connectome Project, Riccelli and colleagues analyzed the variability of three features: cortical thickness, surface area, and gyrification (or the formation of folds in the cortex). In addition, they examined personality data using the NEO Five-Factor Inventory, designed to give numerical values to each of the five factors.
The Human Connectome Project public dataset, an existing collection of neuroanatomical and psychological information, streamlined the scientific process. The researchers used data from more than 500 people. “The age range is from 22 to 36 years old," says Riccelli, "so all of the participants are young and we’re sure they are free from neurological and psychiatric disorders.”
Riccelli’s team found striking correlations between the scores from the five personality variables and the scores for each of the neuroanatomical variables. Subjects with high scores on neuroticism tended to have relatively high levels of cortical thickness in certain regions of the prefrontal cortex while having low surface area and gyrification. Riccelli thinks this may be indicative of behaviors key to neurotic personalities: “(These anatomical features) may be associated with problems in the suppression of reactions," she says, including the regulation of negative emotion. Meanwhile, subjects who scored high in openness exhibited opposite trends: less cortical thickness and greater surface area and gyrification in several prefrontal areas. Riccelli theorizes that this combination of characteristics may be emblematic of cognitive flexibility and creativity, both of which are aspects of openness to experience.
While the results can't prove that the observed brain differences necessarily cause differences in personality—as opposed to coinciding with them for some other reason—each of the five traits was linked positively with certain anatomical features and negatively with others in various regions of the brain.
The prefrontal cortex, the same brain area damaged in Gage’s accident, was among the regions most implicated. “If you think about the case of Phineas Gage,” Riccelli says, “it is quite evident that the prefrontal cortex is related to our behavior and personality. The fact that the prefrontal cortex is widely implicated in the areas of personality is confirmation.” It takes a highly developed physiology to support a multifaceted personality, and the prefrontal cortex, one of the most evolved brain areas in humans, could play an especially significant role.
The anatomical correlates of personality differences may also help explain how personality disorders develop; these disorders can be thought of as extreme manifestations of standard personality traits. Borderline personality disorder, for example, involves a confluence of high neuroticism and low conscientiousness and agreeableness, explains Riccelli. She hopes that her findings will provide an understanding of the biomarkers “that could lead to the identification of risk factors for the development of psychiatric behavior and personality disorders.”
“That’s the hope with all personality neuroscience research,” says Colin DeYoung, a psychologist at the University of Minnesota whose studies have helped to develop the field. “As we understand the neural basis for these different personality traits, it may also help us understand what’s going wrong in various disorders,” offering clues to what makes us—for better or worse—us.