A brain scan might one day predict your voting patterns. That is the implication of a study that found different brain activity among liberals and conservatives asked to carry out a simple button-pushing test. The study implies that our political diversity may be the result of neurological differences.

Researchers have long known that conservatives and liberals score differently in psychological profiling tests. Now they are beginning to gather evidence about why this might be. David Amodio of New York University, US, and his colleagues recruited 43 subjects for their test.

They asked the participants to rate their political persuasion on a scale of -5 to 5, with the lowest number representing the most liberal extreme and the highest number representing the most conservative score.

The participants then had to sit before a computer screen and press one of two buttons depending on whether they saw an “M” or a “W”. They had half a second to make each response, so there was a great deal of pressure to react quickly.


Surprising stimulus

Out of the 500 trials that each subject completed, he or she was presented with the same letter 80% of the time. This meant that the participants felt compelled to press the same button repeatedly.

“You keep seeing the same stimulus over and over, so when the opposite stimulus comes on it’s always a surprise,” says Amodio.

When the less common letter did appear on the screen, the people who identified themselves as more conservative (rating themselves somewhere between 1 and 5 on the initial questionnaire) pressed the “usual” button 47% of the time instead of switching to the correct button.

By comparison, the “liberals” who placed themselves between -5 and -1 on the questionnaire responded more readily to the new signal and achieved the slightly lower error rate of 37%.

Brain recordings taken using electroencephalogram (EEG) technology showed that liberals had twice as much activity in a deep region called the anterior cingulate cortex. This area of the brain is thought to act as a mental brake by helping the mind recognize “no-go” situations where it must refrain from the usual course of action.

Voting prediction

The new findings are “interesting and provocative” because they could perhaps help enable researchers to predict a person’s voting behaviour based on brain scans, says Jordan Grafman, chief of the cognitive neuroscience section at National Institute of Neurological Disorders and Stroke in Bethesda, Maryland, US.

Amodio explains that the fact that liberals achieved higher accuracy on the button-pressing task does not make them “better” than conservatives. “There might be other tasks or situations where a less sensitive or more persistent response might be more adaptive,” such as when new stimuli are distracting, he says.

He also speculates that differences in brain responses might contribute to differences in political views or vice versa.

“Conservatives tend to say that liberals spend too much time thinking and not enough time acting,” comments Matt Newman at Arizona State University in Phoenix, Arizona, US. But “it would be a leap if researchers claim that there is an underlying biological difference that leads you to a particular political orientation.”

He adds, however, that the new finding that conservatives stick with habit is still interesting given that previous studies have found they are more likely to resist change than their liberal counterparts (Psychological Bulletin, DOI: 10.1037/0033-2909.129.3.339).

Journal reference: Nature Neuroscience (DOI: 10.1038/nn1979)