People’s brain activity shows their political affiliation while buying food, study shows

People’s political affiliation can be shown in their brain activity when they carry out mundane chores such as buying food, a new study shows.

How the brain reacts to food purchasing decisions can be used to determine people’s political affiliation with almost 80 per cent accuracy, researchers have found.

Although buying eggs and milk can lack emotional potency and political content, understanding how the neural systems lead people to make indistinguishable choices may help to explain the broader mechanisms of partisanship.

Experts from Iowa State University, the University of Kansas Medical Center, Oklahoma State University, and the University of Exeter measured the brain activity of adult Republicans and Democrats via MRI while they made the food choices.

The two groups didn’t make significantly different decisions about food purchases, but the way their brains activated as they made decisions differed according to their party affiliation.

Republicans showed greater neural activity than Democrats in specific regions of the brain, and Democrats had greater neural activity than Republicans in other regions.

The findings suggest that political orientation might be partially rooted in basic neurocognitive mechanisms that occur even when the choices are non-political. This may help to explain the broader mechanisms of partisanship.

Professor John Crespi, from the Iowa State University, said: “You cannot tell whether someone is a Democrat or a Republican when you see them buy free-range eggs, but if you were to examine their brain activity, you would see that they are using different parts of their brains in that decision. The brain activity predicts the party, not the purchase.”  

Dr Darren Schreiber, from the University of Exeter, said: “We know from studies of twins that about 50% of your political ideology is biologically heritable and that data from your parents allows us to infer your political party with 69% accuracy. So, it is pretty amazing that just the signal from the brain while you’re buying eggs and milk enables us to correctly classify your political party about 80 per cent of the time.”

The fMRI scanner recorded activity in several areas of the brain including the ventromedial prefrontal cortex, which is associated with decision making.

Professor Crespi said: “We can discern your likelihood of being in one party or another from how those brain regions react to what you are choosing even if the choices end up being exactly the same as someone in a different party. I think that is what is intriguing—we can’t tell if you’re a Democrat by the eggs you buy, but by the parts of the brain you use to buy the eggs.

“We gave the subjects $50 but they were told that one of the products they selected would be given to them at the end of the study and its price would be deducted from their $50. So, they went home with either a jug of milk or a carton of eggs and whatever money they had left after the purchase.”

The researchers chose to use milk and eggs in the study because they wanted common grocery items that were indistinguishable by brand, as branding can make purchasing decisions more personal and changes the way we think about them.

Professor Crespi said: “I would be amazed to find that the results do not hold up with other product choices—the parts of your brain that are active when buying a carton of eggs are active when other decisions are made.

“Darren Schreiber’s work was some of the first in this area showing differences seem to be there. There are so few studies on politics and purchasing decisions that also look at brain activity that I’m kind of excited to say this is really a first. There are a few other studies that are in the same spirit, and our predictions hold up when compared with theirs although they did not look at the food choices like we did. The brain is still very much a mystery and papers like this are just like dipping our toes into a very big ocean.”