The study challenges previous findings, showing that the connection between brain anatomy and political beliefs is much more subtle than previously thought. A small but significant link between brain structure and political ideology. The research revealed that conservatives have a slightly larger amygdala, a region of the brain involved in processing emotions, although the difference in size is minimal.
This paper addresses a very interesting question: do liberals and conservatives think and act in fundamentally different ways? The answer is still unclear, and scientists have debated whether there are brain differences related to these ideologies, as well as issues such as risk-taking, impulsivity, and rigidity in thinking.
An important study on this topic was first published in 2011 in the journal Current Biology. The study, led by Kanai and his team at University College London, suggested that people with conservative political orientations have a region of the brain called the amygdala that is slightly larger than liberals. The amygdala is associated with processing negative emotions such as fear and sadness. On the other hand, liberals had more gray matter in another part of the brain, the anterior cingulate cortex (ACC), which is involved in error correction, belief change, and emotion regulation.
This study used MRI scans to analyze the brains of 90 UK college students and was followed by a smaller study of 28 people. Participants rated their political orientation from liberal to conservative. The main finding was that these differences in the brain regions mentioned above suggested a possible link between brain structure and ideology.
However, there were some limitations. The sample was small and fairly homogeneous, mostly composed of middle- and upper-class students. In addition, there were not many participants who identified as extremely conservative, which made it difficult to analyze the entire political spectrum. Even so, the study was groundbreaking and has caught the attention of other researchers.
In 2018, a new study by Nam and colleagues attempted to replicate Kanai’s findings, but with college students in the US. They expanded the analysis to include questions about how fair and legitimate participants believed the social system was.
The study found a relationship between amygdala size and views that the system was fair, but failed to confirm that this relationship applied to conservative political orientation per se. Despite the initial evidence, there are still many uncertainties about how these brain differences relate to political ideology.
One concern is that previous studies used small sample sizes, which could lead to bias in the results. More recent research suggests that to better understand the relationship between the brain and ideology, we need much larger and more diverse samples that include people from different backgrounds and beliefs. Furthermore, political ideology is much more complex than simply saying that someone is liberal or conservative.
In many cases, a person may hold liberal positions on some issues and conservative positions on others. This means that a more nuanced and multidimensional approach is needed to truly understand how political beliefs relate to the brain.
When we talk about political ideology, we can understand it as being comprised of three main issues. The first is issue positioning, which refers to a coherent set of political views on social and economic issues. For example, someone might hold conservative views on issues like “abortion should be illegal” or “a fair society,” or liberal positions on other topics.
The second issue is ideological identity, which refers to the political group with which a person identifies, such as being a Republican or a Democrat in the US. It is worth noting that while it is often assumed that these two forms of ideology, issue positioning, and political identity, are aligned, this is not always the case. A person may identify with a party but hold views that vary from that party’s traditional agendas.
Ideology is often described as a single line that runs from liberal to conservative, or from left to right. In groups where ideas are more homogeneous (i.e. more similar to each other), it makes sense to use this simplified view of a one-dimensional spectrum to understand political orientations. However, in democracies where there is greater diversity of opinion, a single dimension is not sufficient to capture the variety of political positions.
For this reason, researchers often separate opinions into two broad groups: economic issues and social issues. These two groups can vary over time and between different countries, as the needs and concerns of each society change.
Another important point is that, although people may change their political preferences on one issue or another over time, overall, political attitudes tend to remain relatively stable in the long term. To truly understand the complex relationships between people’s political orientations and the structure of the brain, we suggest that it is necessary to differentiate at least four types of ideological constructs:
- Social ideology as self-identification – how a person identifies himself on social issues (more liberal or conservative).
- Economic ideology as self-identification – how a person sees himself on economic issues.
- Social issue positions – the person’s specific views on specific social issues (e.g., same-sex marriage, immigration).
- Economic issue positions – the person’s specific views on economic issues (taxes, income redistribution).
Measures that take all these different facets into account better capture the complexity of political orientations. This also helps us to understand more precisely how these ideological differences are related to brain structure.
For example, using more detailed questionnaires on political orientation can reveal more clearly which parts of the brain are involved in different aspects of political preferences, such as identification with a party or opinions on specific issues.
Using this classification, researchers at the University of Amsterdam (UvA) analyzed the MRI scans of 975 Dutch people aged 19 to 26, representing a representative sample of the Dutch population in terms of education and political preferences.
They linked these scans to questionnaires on ideology. “You can view ideology as a series of positions on different issues or as an identity,” explains first author Gijs Schumacher.
The results show that there is indeed a connection between brain structure and ideology. However, the connection is weaker than expected. Scientists at the UvA have now conducted the largest replication study to date to further investigate the relationship between ideology and brain structure.
The scientists found, as in the English study, that the amygdala of conservative people is slightly larger. The difference in the amygdala was the size of a sesame seed. The average conservative voter is 157 sesame seeds in size, while the average liberal voter is 156 sesame seeds in size.
“This is a small difference, but it’s significant. It suggests that there is a connection between brain anatomy and ideology at some level, but it’s very indirect,” explains co-author Steven Scholte. “It’s notable that we also found this result in our much larger and more representative sample. For example, the English sample didn’t contain any extremely conservative participants, whereas ours did,” says Schumacher.
The scientists also showed that there is no relationship between another area of the brain – the anterior cingulate cortex – and ideology, something that the original study found. But when they extended their analysis to find connections between other areas of the brain, the researchers found a link between the volume of the right fusiform gyrus, an area of the brain important for facial recognition, and more right-wing positions on social and economic issues. The reason for this remains to be seen.
Figure shows sample distributions for ideology, vote choice, and gray matter volume in the anterior cingulate cortex (ACC) and amygdala. (A) Shows the percentage of voters for each party in the election and in the sample. (B) Shows the distribution of progressive to conservative identification (self-positioning) on the economic and social dimensions. (C) Shows the distribution of left/progressive to right/conservative positions on the economic and social dimensions. (D) Shows boxplots to represent the distribution of gray matter volume in the ACC and amygdala. DOI: 10.1016/j.isci.2024.110532
“However, we do not know exactly how conservatism and amygdala size are related,” adds Diamantis, another author of the paper. The amygdala has been studied primarily about threatening situations and fear, but it appears to respond much more broadly to general emotions and to discordant information.
There may be a connection in which the amygdala is larger in individuals who react more strongly to information, which can sometimes result in more conservative views on politics.
Finally, the research suggests that there is no simple dichotomy when it comes to political ideology in the brain. People sometimes talk about blue (Democrat) brains and red (Republican) brains in the American context. This metaphor is tempting but completely misleading, Schumacher says.
In short, while there is some evidence suggesting a link between brain structure and political ideology, these findings are complex and not yet fully understood. What seems clear is that we cannot simply divide people into “liberal brains” and “conservative brains.” The relationship between the brain and politics is multifaceted and depends on many factors beyond biology.
READ MORE:
Is political ideology correlated with brain structure? A preregistered replication
Diamantis Petropoulos Petalas, Gijs Schumacher, Steven H. Scholte
Science, CellPress. DOI: 10.1016/j.isci.2024.110532
Abstract:
We revisit the hypotheses that conservatism positively correlates with amygdala and negatively with anterior cingulate cortex (ACC) gray matter volume.Using diverse measures of ideology and a large and representative sample (Amsterdam Open MRI Collection [n = 928]), we replicate a small positive relationship between amygdala volume and conservatism. However, we fail to find consistent evidence in support of the ideology-ACC volume link. Using a split-sample strategy,we conducted exploratory whole-brain analyses on half the data, preregistered the findings, and then conducted subsequent confirmatory tests that additionally highlight weak, positive associations between the right fusiform gyri and conservatism. This is the largest preregistered replication study in the context of political neuroscience. By using Dutch as opposed to British or American data, we also extend the amygdala-conservatism link to a multiparty, multidimensional political context. We discuss the implications for future investigations of the neural substrates of ideology.
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