A new study suggests a link between individuals’ preference for group-based inequality and the structure of their brains. Researchers report that young adults who score highly on social dominance orientation tend to have less grey matter in the anterior insula, a region associated with empathy and emotion processing, with reward sensitivity also playing a role. The work, published in Current Psychology and led by Jesús Adrián-Ventura of the University of Zaragoza and the Pseudo-Lab research group, hints that social and political worldviews may reflect underlying motivational and emotional differences.
Social dominance orientation is a personality trait that gauges how much a person favours inequality between social groups over equality. Those scoring high tend to view society as naturally divided into superior and inferior groups and often back systems that sustain hierarchies, while lower scorers favour egalitarian relationships and oppose group-based dominance.
The anterior insula, a pocket of brain tissue tucked beneath the frontal, parietal and temporal lobes, is central to detecting bodily signals and processing the emotional experiences of others. The researchers focused on this and other regions to probe possible neural correlates of social dominance.
The study was led by Jesús Adrián-Ventura, a professor at the University of Zaragoza in Spain and a researcher with the Pseudo-Lab research group. “Despite Social Dominance Orientation—the ideological belief that some groups should dominate others—being a central construct in social psychology, its neural underpinnings have received very little attention,” Adrián-Ventura told PsyPost. “We aimed to contribute to filling this gap, while also exploring predictors related to personality and motivation. Ultimately, we sought to investigate how stable brain traits (e.g., brain anatomy) and motivational drives jointly predispose individuals to endorse social hierarchies and inequality.”
Participants included 99 healthy young adults aged 18 to 30 from a university campus in Spain, with 62 women and 37 men. After cognitive screening and psychological surveys, two participants with extreme brain-volume values were excluded, leaving 97 for neuroimaging analyses. Each participant completed an eight-item survey measuring social dominance orientation and a 24-item survey assessing sensitivity to reward. Brain scans were obtained with high-resolution 3-Tesla magnetic resonance imaging.
Using voxel-based morphometry, the team measured grey matter volume in predefined brain regions of interest and adjusted for age and head size. They did not include sex as a separate factor, reasoning that head-size adjustment already captures much of the sex-related variation in brain volume.
The analyses showed that higher social dominance orientation scores were linked to less grey matter volume in both the left and right anterior insula. The correlations were modest but statistically meaningful after stringent correction: r = -0.30 for the left insula and r = -0.29 for the right insula. An exploratory whole-brain scan found no significant associations outside the predefined regions, indicating the insular finding was specific to those targeted areas.
Unlike a prior study conducted in Singapore, this Spanish sample did not reveal significant associations between social dominance orientation and the amygdala or the ventromedial prefrontal cortex, areas implicated in emotion regulation and value weighing. Adrián-Ventura suggested that cultural factors might explain the discrepancy: “Because that prior study involved Singaporean Chinese adults while ours involved a Spanish sample, we suspect this discrepancy might reflect cultural differences. It suggests that while the anterior insula’s involvement might be a universally preserved pathway, other neural mechanisms of social dominance could be highly sensitive to distinct cultural landscapes.” Methodological differences in how brain regions are outlined could also play a role, the authors note.
Behaviorally, social dominance orientation correlated positively with reward sensitivity (r = 0.33). In a predictive model, the researchers found that insula volume, age and head size could explain up to 29 per cent of individual differences in social dominance orientation, with reward sensitivity contributing an additional 10 to 11 percentage points beyond these factors.
“The effects we observed are quite substantial,” Adrián-Ventura said. “Importantly, structural brain features and personality traits are highly heritable and exhibit strong stability across the lifespan. This highlights that preferences for social hierarchies are not merely transient attitudes but may be rooted in early developmental and genetic factors.”
Expert outside the study was supportive but cautious. David V. Smith, an associate professor of psychology and neuroscience at Temple University, noted that the findings offer “interesting leads for investigating how motivational processes relate to these attitudes.” He cautioned that larger studies are needed before treating the pattern as well established, adding that the Spanish results partly replicate the insula finding while not finding effects in other tested regions.
The authors’ line of enquiry sits alongside earlier work. In a 2025 PsyPost piece, Adrián-Ventura and colleagues reported that higher scores on anti-hierarchical aggression—a facet of left-wing authoritarianism—were linked to a thinner cortex in the right anterior insula in a nearly identical group of Spanish young adults, albeit measured as cortical thickness rather than grey matter volume. The authors note that different ideological stances may relate to the same brain region in complex ways, and that methodological differences could contribute to divergent results.
The researchers propose that the anterior insula findings may reflect differences in socio-emotional processing. Since the anterior insula helps people attune to others’ distress and feelings, having less grey matter in this region could relate to reduced empathy. If that is the case, a reduced sensitivity to others’ feelings together with a strong drive to obtain rewards could help explain why some individuals endorse hierarchical social arrangements.
“Together, our results reveal an underlying neurobiological and motivational predisposition associated with a higher social dominance orientation,” Adrián-Ventura concluded. He stressed that the study is cross-sectional and cannot establish causality or determine whether empathy mediates the relationship. He also cautioned that generalising the findings beyond young Spanish university students requires further cross-cultural research.
Smith echoed the call for caution, saying the anatomical findings should be considered preliminary and that the small sample size warrants replication, ideally with pre-registered designs and additional measures of empathy and group-based preferences. He also highlighted the need to test whether the association persists when sex is explicitly included in analyses.
The paper, titled Neuroanatomical correlates of social dominance orientation and the contributing role of reward sensitivity, is authored by Jesús Adrián-Ventura, Angelo Fasce, Anna Miró-Padilla, Anastasia Cherednichenko, César Ávila, and Diego Avendaño.
