Take 99 Spanish adults between 18 and 30, scan their brains in a 3-Tesla MRI, and hand each of them two questionnaires: one measuring how strongly they prefer group-based hierarchy over equality, the other measuring how strongly they chase reward. Then look for a pattern in the gray matter. That’s the design behind Neuroanatomical correlates of social dominance orientation and the contributing role of reward sensitivity, published in Current Psychology by Jesús Adrián-Ventura of the University of Zaragoza and five co-authors, covered Oct 8, 2026 by PsyPost.

The finding, in short: people who score higher on preferring hierarchy between groups have measurably less gray matter in the anterior insula — a brain region bound up with sensing your own bodily states and, in a large body of other research, with registering what other people are feeling. Mozi never saw an MRI. But sometime in the 5th century BCE, he sat down and diagnosed the exact same failure mode in plainer terms: the reason the world is at war with itself is that people don’t treat other families, and other states, as their own. His fix had a name — jian’ai, impartial caring — and it was aimed at precisely the gap this study just measured in cubic millimeters of cortex.

The Quick Verdict

Question	What we found
What was studied?	Whether a preference for group-based social hierarchy (social dominance orientation, or SDO) shows up in brain structure and personality
Who ran it?	Jesús Adrián-Ventura and colleagues, University of Zaragoza
Where and when?	Current Psychology; covered Oct 8, 2026 by PsyPost
Sample	99 Spanish adults, ages 18–30 (97 included in the brain-imaging analysis)
Method	8-item SDO scale, 24-item reward-sensitivity measure, 3-Tesla MRI, voxel-based morphometry
Core finding	Higher SDO correlated with less gray matter in the left anterior insula (r = -0.30) and right anterior insula (r = -0.29)
Second finding	SDO also correlated positively with Sensitivity to Reward (r = 0.33); insula volume plus reward sensitivity together explained 29% of the variance in SDO scores
What Mozi already argued	In the Mozi (5th century BCE), social chaos traces to partiality — not regarding other families’ and states’ interests as one’s own; his prescribed fix was jian’ai, impartial caring

The Quick Version

A 2026 brain-imaging study found that people who prefer hierarchy between groups have less gray matter in the anterior insula, a region tied to registering bodily and emotional states, and that this preference also tracks with a reward-chasing personality trait. Mozi made the structural version of this argument twenty-four centuries earlier: the world’s conflicts come from treating outsiders’ interests as foreign territory, and the remedy isn’t a nicer attitude — it’s extending care past the border where it currently stops.

What the Study Actually Found

Social dominance orientation, as psychologists use the term, isn’t the same as simply enjoying being in charge. It’s a preference for the idea that groups should be ranked — that some groups belong on top and others belong underneath them, and that this is how things ought to work. People high in SDO don’t just tolerate inequality between groups. They tend to want it.

Adrián-Ventura’s team wanted to know whether that preference shows up anywhere besides a questionnaire. So they put 97 of their 99 participants through structural MRI scans and ran voxel-based morphometry, a technique that maps gray matter volume across the whole brain and looks for where it correlates with a trait of interest. The anterior insula turned out to be where it correlated. Scored higher on the SDO scale, and your left anterior insula ran smaller (r = -0.30). Same for the right (r = -0.29). Both relationships held up as statistically real, not noise.

The anterior insula isn’t an empathy organ in some simple, one-to-one sense — brains don’t work that way — but it’s one of the most consistently implicated regions in interoception (sensing your own heartbeat, hunger, pain) and, downstream of that, in registering someone else’s distress as something that matters to you. Reduced volume there doesn’t prove reduced empathy. It’s a structural correlate in a region the broader literature keeps landing on when empathy is the thing being measured.

The second half of the finding is the one that keeps this from being a tidy “mean people have smaller brains” headline. SDO also correlated positively with Sensitivity to Reward, a personality trait describing how strongly someone is drawn toward pursuing rewards — status, resources, winning — once they’re in view (r = 0.33). Put the insula measurement and the reward-sensitivity score together, and they explained 29% of the differences between people in how strongly they preferred hierarchy. That’s a meaningful chunk of a complex attitude accounted for by two measurements that have nothing to do with someone’s stated politics, upbringing, or the news they consume. As Adrián-Ventura put it to PsyPost, the pattern suggests “preferences for social hierarchies are not merely transient attitudes but may be rooted in early developmental and genetic factors.”

What Did Mozi Mean by Jian’ai?

Jian’ai (兼愛), usually translated “impartial caring” or “universal love,” is Mozi’s term for concern that doesn’t vary by relationship — caring about a stranger’s family, a rival state’s welfare, the same way you care about your own. In the Mozi, he argues this isn’t a sentimental ideal. It’s the specific structural fix for a world where war, theft, and usurpation all trace back to one habit: treating “not mine” as a reason to care less.

Mozi (c. 470–391 BCE) wasn’t interested in moral poetry. He ran something closer to a diagnostic. Go through the catalog of the world’s disorders, he argued in the chapters on universal love — a thief doesn’t regard another family’s house as his own concern, so he robs it; a minister doesn’t regard his lord’s state as his own, so he schemes against it; one state doesn’t regard another state as its own, so it invades it. The pattern, as the Internet Encyclopedia of Philosophy summarizes it, is that “the cause of the world’s troubles lies in people’s tendency to act out of a greater regard for their own welfare than that of others, and that of associates over that of strangers.” Partiality isn’t a minor character flaw sitting next to the real causes of conflict. For Mozi, it is the cause, traced all the way down.

His remedy wasn’t an appeal to feel more warmly toward strangers in the abstract. It was structural: treat other people’s parents, families, and states as objects of the same regard you give your own, and the specific behaviors that produce chaos — theft, usurpation, war — lose their logic, because they all depend on a gap between “mine” and “not mine” that jian’ai is designed to close.

Why Does Favoring Your Own Group Shrink Empathy?

1. Reward sensitivity does some of the work. People higher in SDO were also more drawn to pursuing status and winning once it came into view. A hierarchy that puts your group on top is, among other things, a reward — and a brain tuned to chase reward has less structural and motivational room left over for registering what the losing side of that hierarchy is feeling.
2. The insula is where “mine” gets felt, not just thought. Interoception — sensing your own internal states — and empathy for others appear to share overlapping neural territory. A region doing less work on “what does this feel like” plausibly does less work on “what would that feel like to someone else,” including someone outside your group.
3. Hierarchy preference isn’t only a belief; it’s tied to anatomy and motivation. The study’s own framing is careful here: 29% of the variance in SDO explained by brain structure and reward sensitivity leaves most of it unaccounted for. But that 29% is still evidence against treating group-based favoritism as pure ideology, picked up entirely from parents, parties, or culture.
4. Partiality and empathy compete for the same resource. Mozi’s account and this study point at the same structural idea from opposite directions: he argued care has to be deliberately extended past the self/other line because it doesn’t go there on its own; the study found a physical correlate of exactly the region most responsible for making that extension happen automatically.

Why the Study and the Philosophy Rhyme

The connection here isn’t “a Warring States philosopher predicted a Spanish MRI study.” It’s narrower, and it holds up better for being narrower: Mozi’s specific claim was that the behaviors driving social conflict — theft, usurpation, war — all share one upstream cause, a failure to regard outsiders’ interests as one’s own. This study found a structural and motivational correlate of exactly that failure, sitting in a brain region linked to registering others’ internal states, in people who report wanting their own group ranked above others.

It connects directly to Hierocles’ circles of concern, the Stoic image of ethical life as concentric rings — self, family, community, humanity — that the work of ethics is supposed to pull inward, collapsing the distance between the inner rings and the outer ones. Mozi is making a harder, more absolute version of the same argument: not just pull the rings closer together, erase the ranking between them entirely. Hierarchy preference, in both frameworks, is what happens when the rings stop moving.

It also sits close to the Stoic concept of oikeiosis, the idea that moral development is a process of widening what counts as “one’s own” until it includes people who started out as strangers. The brain-imaging finding gives that widening a physical face: a smaller anterior insula isn’t evidence that oikeiosis is impossible for someone, but it’s a plausible account of why the widening would take more deliberate effort for some people than others.

And it connects to Mencius’s argument about extending care outward — Mencius’s claim that moral failure is a failure to push an existing feeling of care past its current border, not an absence of the feeling itself. Mozi’s jian’ai is the blunter cousin of that idea: don’t wait for a trigger, like Mencius’s king waiting to feel pity for an ox. Close the gap between self and other on principle, by argument, regardless of whether anything personal ever prompts it.

The Gap Mozi Didn’t See Coming

Here’s where the comparison gets more interesting than a clean match, and it’s worth sitting with instead of smoothing over.

Mozi argued for jian’ai the way a logician argues for a conclusion: lay out the costs of partiality, show that impartial care produces better outcomes for everyone including the partial person, and expect the argument itself to move people. He assumed, more or less, that failing to care impartially was a correctable error in reasoning or habit — something a good argument, backed by a ruler’s rewards and punishments, could fix.

This study complicates that assumption without refuting it. If hierarchy preference is bound up with anterior insula volume and a temperament-level trait like reward sensitivity — the kind of thing Adrián-Ventura suggests may be “rooted in early developmental and genetic factors” — then for some people, the gap jian’ai is supposed to close isn’t sitting at the level of belief, where an argument can reach it. It’s sitting partly in structure and motivation, which arguments reach less directly, if at all. Mozi’s confidence that chaos was a correctable error, not a built-in tendency for at least some people, is the part twenty-four centuries didn’t get around to testing until now.

What This Study Doesn’t Show

Be precise about the size of this. The framing invites more confidence than the data earns.

Correlation, Not Causation

A cross-sectional brain scan can’t tell you whether less anterior insula gray matter produces hierarchy preference, whether a lifetime of hierarchical thinking shapes the insula, or whether some third factor drives both. The researchers are explicit that causal direction isn’t established here.

A Small, Specific Sample

Ninety-seven brains is a workable number for this kind of structural analysis, but it’s a small sample by the standards of brain-anatomy research generally, and it’s drawn entirely from Spanish university-aged adults. Whether the same pattern holds in a 55-year-old in Seoul or Lagos is untested.

No Pre-Registration

The study wasn’t pre-registered, which matters for how much weight any single correlation coefficient should carry, even a statistically significant one.

Empathy Was Never Directly Measured

This is the limitation that matters most for this post’s own argument. The study measured SDO, reward sensitivity, and gray matter volume. It did not administer an empathy questionnaire or behavioral empathy task. The anterior insula’s link to empathy comes from other research, not from this dataset. Calling the insula “empathy-related” is well-supported by the broader literature; calling this specific study proof that hierarchy-preferring people have less empathy is more than the data directly shows.

What Actually Follows From This

1. Group favoritism isn’t purely a belief you can out-argue. If part of what sustains a hierarchy preference is structural and motivational rather than purely ideological, changing minds may take more than better information — the kind of repeated, concrete contact across group lines that actually moves felt concern, not just stated opinion.
2. Don’t mistake “rooted in brain structure” for “fixed forever.” Gray matter volume and reward sensitivity aren’t immutable; both show real plasticity in response to sustained experience. Mozi’s confidence that impartial care could be built, not just discovered, still has a case — it just may need more than a good argument to do the building.
3. Ask where your own circle currently stops. Mozi’s test wasn’t capacity for caring well — most people clear that bar. It was whether that caring travels past people who already feel like yours. The honest version of this question doesn’t require an MRI — just a willingness to notice where the care quietly runs out.

Mozi never ran a brain scan and never met a reward-sensitivity questionnaire. He had a list of the world’s disorders and a conviction that every one of them traced back to the same habit: treating someone else’s family, or someone else’s state, as a separate category of concern from your own. Twenty-four centuries later, a team in Zaragoza found a region of cortex and a cluster of motivation that moves in exactly the pattern he described, smaller and more reward-hungry in the people least inclined to extend care past their own group’s border. The argument was never that partiality is evil. It’s that it’s a gap — in reach, in structure, in habit — and gaps, unlike villains, can at least in principle be closed.

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This post discusses a 2026 study published in Current Psychology and Mozi’s writings on impartial caring (jian’ai) from the Mozi (5th century BCE). The study’s findings are correlational, drawn from 97 Spanish adults aged 18–30, and did not directly measure empathy — they describe a structural and motivational association with social dominance orientation in that specific population, not a general or causal claim about empathy, brain anatomy, or group favoritism in people elsewhere.