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

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

“A slightly larger amygdala simply highlights a brain’s increased sensitivity to issues related to [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 as big as a shelled peanut — and the difference between conservatives and liberals is about the size of a sesame seed, Petalas said.

Having a larger amygdala could be attributed to genes, the environment, or most likely, a combination of the two, he added. It is possibly related to a “larger proclivity for understanding danger.”

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

Petalas’ team examined brain scans from 928 Dutch adults 19 to 26 years old.

The researchers paired the brain data with insight into the participants’ politics. The volunteers were asked about their social and economic identity, such as where they view themselves on a sliding scale of progressive to conservative and which political party they identify with.

Other questions touched on their social and economic ideology, like where they stand 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 matters, as well as identification with progressive or conservative ideals,” said Petalas, a political psychology and neuroscience researcher at the American College of Greece. “It’s really not just about the left or the right.”

Petalas 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.”

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

These findings spurred headlines in 2011 like “Conservatives Big on Fear, Brain Study Finds” and “Conservatives Are Scaredy Cats, Science Says,” referencing the amygdala’s role in processing fear and anxiety.

“It’s no surprise that findings like that were ‘framed’ to fuel polarization,” Petalas told The Post. “The same study found that the ACC was larger in liberals, but I’m guessing there were less loud headlines around that finding: Liberals big on error detection I guess doesn’t sell that much.”

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

They found an association between conservatism and the volume of grey matter in the amygdala — though this connection was three times weaker compared to the 2011 study.

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