Where does our personal politics come from? Does it trace back to our childhood, the views that surround us, the circumstances we are raised in? Is it all about nurture – or does nature have a say through the subtle levers of DNA? And where, in all of this, is the brain?

Take a study published last week. Researchers in Greece and the Netherlands examined MRI scans from nearly 1,000 Dutch people who had answered questionnaires on their personal politics.

The work was a replication study, designed to see whether the results from a small 2011 study, bizarrely commissioned by the actor Colin Firth, stood up. Firth’s study, conducted at UCL, reported structural differences between conservative and liberal brains. Conservatives, on average, had a larger amygdala, a region linked to threat perception. Liberals, on average, had a larger anterior cingulate cortex, a region involved in decision-making.

What, then, does it mean? Do people with larger amygdalas feel more threatened and so tend towards conservatism? Or do conservatives feel more threatened and develop a slightly larger amygdala as a result? “It’s impossible to know, using such correlational data, what causes what,” said Dr Diamantis Petropoulos Petalas, the first author on the study.