Left-wing brain, right-wing brain

Are political preferences the product of our biology, our brain, or simply of the environment in which we are educated? In this series of articles cross-posted in French in the Québec version of the Huffington Post, I have a look at the studies that have explored these questions in recent years.

The questions surrounding the scientific study of political preferences are complex and researchers may encounter numerous obstacles on their way to understanding how the brain controls political behaviors. Among these obstacles are the variations in how left-wing and right-wing are defined in different countries. Many political psychology studies come from the United States, a country in which for instance the right-wing is associated with moral ideas such as those that relate to abortion and same-sex marriage. In other places like Québec, the discourse of right-wing politicians is mainly on liberty and economy, and the moral and religious subjects are left aside. Thus we have to be careful when interpreting studies identifying differences between conservatives and liberals; in almost every case the national context in which these political preferences are expressed is not considered by the study. But the results can be interesting anyway.

Researchers in psychology typically use forms that are sent to large portions of the population, asking them questions about their lifestyle and their political preferences. They then search for links that could exist between the variables.

One of the most interesting variables which was discovered to be correlated to political preferences in recent years is sensitivity for disgust. In 2011, Yoel Inbar and colleagues1 have analyzed the responses of more than 30 000 subjects to twenty-five questions related to disgust. One example of the questions that may appear on those forms is: ‘‘You take a sip of soda, and then realize that you drank from the glass that an acquaintance of yours had been drinking from. Rate your level of disgust on a scale from 0 to 4.’’.

The results of this and other similar studies is that conservatives show a stronger sensitivity for disgust, even on questions that are not linked to politics2. These studies are interesting because they establish a link between political preferences and an emotion, disgust, and we know a little more about the neurobiological basis of disgust.

Another group of researchers got interested in the regions of the brain known for their link with disgust and have tried to establish if differences in the structure of these regions might be correlated to political preferences3. Typically in those studies, authors measure the volume of gray matter for each region of the brain. This measure can be obtained by a MRI scanner. The volume of gray matter indicates the thickness and density of the layer of neurons in a given region of the brain. Generally, we interpret increased gray matter volume as being related to increased use of the particular area, although this is quite hard to demonstrate for each study.

The amygdala, a region which is known to be activated by fear and disgust.

MRI image from Amber Rieder, Jenna Traynor, Geoffrey B Hall, released under the Creative Commons license.

The study established that differences can be detected between the brains of conservatives and liberals. One of the interesting observations is that gray matter volume in the amygdala seems slightly greater in the brains of conservatives than those of liberals. The amygdala is a deep region of the brain, known to be activated by fear and disgust.

The correlation that was found between the volume of gray matter and conservatism is very weak. For instance, one could not simply look at the brain scan of an individual and determine with great precision whether he is conservative or liberal. However the study suggests that subtle differences in the brain anatomy might be linked to political preferences.

Taken together, these studies raise many questions. First, what is the causality link? Are people more conservative because they have an a priori sensitivity for disgust or the other way around? Were the differences in brain anatomy present before the development of political preferences, during childhood, or are they a consequence of the adoption of those preferences?

These questions are still not addressed. Meanwhile researchers have access to an array of other methods to study the links between neurobiology, psychology and political choices. One of these methods allows us to determine whether traits such as political orientation can be inherited genetically. This will be the subject of my next article.


1. Inbar Y., Pizarro D.A., Lyer R., Haidt J. (2012) Disgust sensitivity, political conservatism, and voting. Social Psychological and Personality Science 3:537-544.

2. Inbar Y., Pizarro D.A., Bloom P. (2009) Conservatives are more easily disgusted than liberals. Cognition and Emotion 23:714-725.

3. Kanai R., Feilden T., Firth C., Rees G. (2011) Political Orientations Are Correlated with Brain Structure in Young Adults. Current Biology 21:677-680.

2 thoughts on “Left-wing brain, right-wing brain

  1. Pingback: Left-wing brain, right-wing brain | BrainFacts....

    • This is a very good question. It’s not entirely settled down for scientists and I would say it might be even more difficult for people in their daily lives because there might be a continuum and the divide between the two might be blurry, with some people being conservative on some issues and liberal on others.

      The literal meaning of conservatism involves the tendency to defend traditional institutions, but the word has evolved and is often use interchangeably with “right-wing”. The literal definition would not work in a very left-wing country, where most right-wing people are, in that sense, anti-conservatism, they want the country to change.

      Typically then, if we go with what it is to be right-wing, it would involve being against an heavy involvement of the state in healthcare or education for instance. Some would point out that the aspects of the state that are authoritarian (such as police, justice system, and military) are less problematic to right-wing people. Finally the form of argumentation in right-wing people can include references to natural law, order, purity, or divinity, while left-wing people tend to base their political argumentation on well-being, fairness and openness.

      Again, this is all very blurry and a lot remain to be discovered. If you are interested in the subject I recommend reading Jonathan Haidt’s book.

      Flag as inappropriate

  2. Pingback: What is a Left Winger?

Leave a Comment