By AMIE NINH
The differences between liberals and conservatives run wide and deep, and a new study suggests they may even be reflected in the ery structure of their brains.
In the study, led by Ryota Kanai of the University College London, people who identified themselves as liberals generally had a larger anterior cingulate cortex — a comma-shaped region near the front of the brain that is involved in decision-making. By contrast, those who identified as conservatives had larger amygdalas — almond-shaped structures that are linked with emotional learning and the processing of fear. (More on TIME.com: In Politics, It's Survival of the Fittest, Literally)
These structural differences, the authors suggest, support previous reports of differences in personality: liberals tend to be better at managing conflicting information, while conservatives are though to be better at recognizing threats, researchers said. "Previously, some psychological traits were known to be predictive of an individual's political orientation," said Kanai in a press release. "Our study now links such personality traits with specific brain structure."
For the study, Kanai and his colleagues asked 90 young adults to rank their political views on a five-point scale from very liberal to very conservative. Then, the volunteers underwent structural MRI scans, which revealed "substantial differences" in brain structure. (More on TIME.com: The Politics of Perceiving Skin Color)
This is not the first attempt to locate the biological roots of party affiliation. In an October 2010 study, researchers from the University of California, San Diego, and Harvard University identified a "liberal gene" — a variant called DRD4-7R, which affects the neurotransmitter dopamine — that has been linked with a personality type driven to seek out new experiences.
Another study from the University of Nebraska found that liberals and conservatives had different reactions to "gaze cues" — whether they tended to look in the same direction as a face on their computer screen. Liberals were more likely than conservatives to follow another person's gaze, suggesting that people who lean right value autonomy more; alternative explanations suggest that liberals might be more empathetic, or that conservatives are less trusting of others. (More on Time.com: Is There Any Biology Behind Our Political Affiliations?)
The theories are best guesses. And Kanai qualifies the findings of his own study, acknowledging that political orientation is complex, and can fall into more than just two categories. In addition, the study doesn't answer whether brain structure influences political preferences or vice versa: it's possible that the shape of the brain changes over time with a person's experiences — and with his or her changing political views.
So, despite increasing evidence suggesting biological differences between liberals and conservatives, Kanai warns against reading too much into the findings. "It's very unlikely that actual political orientation is directly encoded in these brain regions," he said. "More work is needed to determine how these brain structures mediate the formation of political attitude." (More on TIME.com: Why We Form Societies: It's Our Big Babies)
The study is published in the April 7 issue of Current Biology.