Summary: A new study finds that conservative voters have slightly larger amygdalas than progressive voters, but the relationship between brain structure and political ideology is more nuanced than earlier research suggested.
Estimated reading time: 7 minutes
Conservative voters have slightly larger amygdalas than progressive voters—by about the size of a sesame seed. This finding comes from a new study published in the Cell Press journal iScience, which revisited the idea that progressive and conservative voters have identifiable differences in brain morphology. The research, conducted with a sample size ten times larger and more diverse than the original study, confirms a relationship between amygdala size and political views but fails to find a consistent association between politics and the anterior cingulate cortex (ACC).
Nuanced Relationship Between Brain and Politics
“It was really a surprise that we replicated the amygdala finding,” says first author and political psychology and neuroscience researcher Diamantis Petropoulos Petalas of The American College of Greece and member of the HotPoliticsLab at the University of Amsterdam. “Quite honestly, we did not expect to replicate any of these findings.”
The study used pre-existing MRI brain scans from 928 individuals aged 19-26 whose levels of education and political identities were representative of the Dutch population. This larger, more diverse sample allowed researchers to examine the relationship between brain structure and political views along a continuum from left- to right-wing, rather than the binary system typical in two-party political landscapes.
Petropoulos and his colleagues looked at participants’ “ideology” from various angles, including their political identity and stance on socioeconomic issues. This multidimensional approach allowed them to compare brain structures along different aspects of progressivism and conservatism.
Amygdala Size and Political Views
The study found that the relationship between amygdala size and conservatism was three times weaker than reported in the original study. Petropoulos explains the potential significance of this finding:
“The amygdala controls for the perception and the understanding of threats and risk uncertainty, so it makes a lot of sense that individuals who are more sensitive towards these issues have higher needs for security, which is something that typically aligns with more conservative ideas in politics.”
Interestingly, the association between amygdala size and conservatism depended on the political party that the individual identified with. For example, participants who identified with the socialist party, which has radically left-wing economic policies but more conservative social values, had on average more gray matter in the amygdala compared to other progressive parties.
Multi-Party System Reveals Spectrum of Ideologies
The study’s setting in the Netherlands, with its multi-party system, allowed for a more nuanced examination of the relationship between brain structure and political ideology. Petropoulos notes:
“The Netherlands has a multi-party system, with different parties representing a spectrum of ideologies, and we find a very nice positive correlation between the parties’ political ideology and the amygdala size of that person. That speaks to the idea that we’re not talking about a dichotomous representation of ideology in the brain, such as Republicans versus Democrats as in the US, but we see a more fine-grained spectrum of how political ideology can be reflected in the brain’s anatomy.”
Anterior Cingulate Cortex and Other Brain Regions
Unlike the original study, this research did not find any association between conservatism and a smaller volume of gray matter in the ACC, a brain region involved in error detection, impulse control, and emotional regulation.
The researchers also extended their analysis to examine potential associations between political identity and other regions of the brain. This analysis uncovered a positive association between the gray matter volume in the right fusiform gyrus, a region in the temporal lobe that is essential for visual and cognitive functions, and economic and social conservatism.
Implications and Future Research
While these findings provide valuable insights into the relationship between brain structure and political ideology, the researchers caution against drawing overly broad conclusions. The differences in brain structure between conservative and progressive voters are small, and the relationship between brain anatomy and political views is complex and multidimensional.
Petropoulos suggests that future research should focus on the functional connections between the amygdala and different parts of the brain:
“I think the future of this endeavor to identify political orientations in the brain will be to look more towards functional connectivity network and neural synchrony studies—how brain networks organize and synchronize between individuals, and whether there are differences in this synchronization when individuals with difference political ideologies consume similar content.”
As our understanding of the brain’s role in shaping political views evolves, it’s clear that the relationship between biology and ideology is far more nuanced than previously thought. This research underscores the importance of large-scale, diverse studies in uncovering the complex interplay between brain structure and political beliefs.
Quiz
- How much larger is the amygdala of conservative voters compared to progressive voters, according to the study?
- What brain region, previously thought to be associated with political views, did not show a consistent relationship in this study?
- Which country’s multi-party system was used for this research?
Answer Key:
- About the size of a sesame seed
- The anterior cingulate cortex (ACC)
- The Netherlands
Further Reading
Glossary of Terms
- Amygdala: A region of the brain involved in processing emotions, particularly fear and threat detection.
- Anterior Cingulate Cortex (ACC): A brain region involved in error detection, impulse control, and emotional regulation.
- Gray Matter: The darker tissue of the brain and spinal cord, consisting mainly of nerve cell bodies and branching dendrites.
- Fusiform Gyrus: A region in the temporal lobe essential for visual and cognitive functions, including facial recognition.
- Voxel-Based Morphometry: A neuroimaging technique that allows investigation of focal differences in brain anatomy using statistical approaches.
- Functional Connectivity: The temporal correlation between spatially remote neurophysiological events in the brain.
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