Conservatives and liberals have different brain structures – here’s how

Forget crowd size — a new study confirms that conservatives boast slightly larger amygdalas, the part of the brain that plays a key role in identifying and responding to potential threats, compared to liberals.

“A slightly larger amygdala simply highlights the brain’s increased sensitivity to issues related to it [the] need for security, reduction of uncertainty and threat, or perhaps more careful processing of negative stimuli,” study author Diamantis Petropoulos Petalas told The Post.

The amygdala is about the size of a shelled peanut — and the difference between conservatives and liberals is the size of a sesame seed, Petropoulos said.

Having a larger amygdala can be attributed to genes, environment, or more likely, a combination of the two, he added. It is likely related to a “greater propensity to understand risk.”

Petropoulos’ research, published Thursday in the Cell Press iScience journal, aimed to replicate a widely criticized 2011 University College London study of only 90 participants.

Petropoulos’ team examined brain scans of 928 Dutch adults aged 19 to 26.

The researchers combined the brain data with the participants’ knowledge of politics. Volunteers were asked about their social and economic identity, such as where they see themselves on a sliding scale from progressive to conservative and with which political party they identify.

Other questions touched on their social and economic ideology, such as their stance on women’s and LGBTQ rights, income inequality, and profit sharing.

“We see ideology as a complex, multidimensional product that includes different attitudes on social and economic issues, as well as identification with progressive or conservative ideals,” said Petropoulos, a political psychology and neuroscience researcher at the American College of Greece. “It’s really not just about left or right.”

Petropoulos said his team did not expect to replicate any findings from the 2011 study.

Oscar winner Colin Firth co-authored that research, which was called “the first neuroscientific evidence for biological differences between liberals and conservatives.”

This study found that compared to liberals, conservatives tend to have larger amygdalas and smaller anterior cingulate cortices (ACC), which are involved in error detection, impulse control, and emotional regulation.

These findings prompted headlines in 2011 such as “Conservatives are big on fear, brain study finds” and “Conservatives are scaredy cats, says science,” referring to the amygdala’s role in processing fear and anxiety.

“It’s not surprising that such findings have been ‘framed’ to fuel polarization,” Petropoulos told The Post. “The same study found that ACC was bigger among liberals, but I think there were fewer headlines about that finding: Liberals are big on spotting mistakes, I guess they don’t sell as much.”

In the new research, Petropoulos and his colleagues failed to identify a consistent link between politics and ACC.

They found a link between conservatism and gray matter volume in the amygdala – although the link was three times weaker than in the 2011 study.

The team is calling for further research into the “complex relationship” between brain structure and political beliefs.