Ever wonder why your stance on such hot-button issues as immigration or gay marriage feels so self-evident, while someone else finds the opposite opinion so obviously correct? There are various reasons for this, but researchers have just documented a startlingly basic one:
Your brain is different from his brain.
A research team led by Gary Lewis, a postdoctoral research fellow at the University of California, Santa Barbara's Sage Center for the Study of the Mind, has found structural differences between the brains of individuals who have different moral values.
We’re not just talking about differences in the way the brains function. Rather, they have documented significant variations in the actual volume of gray matter. That’s a big deal, and it “suggests a biological basis for moral sentiment,” Lewis and his colleagues write in the Journal of Cognitive Neuroscience.
“This does not explain political attitudes, but it improves our explanation of political attitudes,” said New York University psychologist Jonathan Haidt, who developed the framework of moral attitudes used by Lewis and his team, but did not participate in the study. “Slight differences in brain structure and function make people more prone to develop one ideology or another.
“Having these pictures will make it easier for people to believe that, when we look at questions like taxes or gay marriage or work-to-welfare rules, we’re not perceiving the same reality.”
The experiment, conducted at University College London, featured 70 healthy adults in the early to mid 20s. All had high-resolution scans taken of their brains.
In addition, they each filled out Haidt’s Moral Foundations Questionnaire, which reveals attitudes towards five moral realms: harm/care, fairness, in-group loyalty, deference to authority, and purity/sanctity. The first two promote individual freedom and self-expression; the final three bind societies together.
Their score on the harm/care foundation was measured by their response to statements such as “Compassion for those who are suffering is the most crucial virtue.” Their score on in-group loyalty was measured by their response to such statements as “It is more important to be a team player than to express oneself.”
Lewis and his colleagues found a clear association between specific brain structures and participants’ scores on the different moral planes. For example, they found people who are highly attuned to ideas of being fair and not harming others had higher volume of the left dorsal medial prefrontal cortex, which has been linked to the organization of basic behavior-guiding principles.
That region of the brain “appears to be involved when we represent the thoughts and intentions of other people, and so is believed to be a core hub of human social cognition,” Lewis noted. “It makes some sense, then, that this region should be associated with harm/care and fairness, as one element of such sentiment is the capacity to represent the concerns and states of others.”
Most interesting to Haidt, Lewis and his colleagues found people who scored high in purity/sanctity—values associated with religious conservatism—had higher volume of a brain region called the anterior insula. “Many other studies have found relationships between disgust and the insula, so that’s quite believable,” he said.
So how does a bulkier insula translate into socially conservative views? The link, according to Haidt, is disgust.
“People who have a bigger right insula—that is, if you have got more neurons in the right insula—may be more prone to feelings of disgust,” he explained. “When you’re disgusted by something—say, deviant sex of some sort—you tend to come up with reasons why it’s wrong.”
In other words, it’s easier to live and let live when someone’s actions evoke an emotionally neutral response.
Lewis concedes that this data does not reveal “whether brain structure is a cause of moral values, or vice versa.” He hopes to address that chicken-or-egg question in future research, perhaps following young people for extended periods to chart their developing views and changing brains.
Haidt is pretty sure of what he’ll find. “I find it very unlikely that these differences in brain structure came about from (different experiences) during childhood,” he said. “It’s much more likely they were innate. The brain structures of identical twins are nearly identical.”
But he cautioned that being born with certain innate tendencies does not mean one is preordained to think and feel a specific way.
“The different brain structures are not decisive,” he said. “They do not perfectly predict where you end up. In absolute terms, your local political and moral culture is going to be a bigger determinant than these relative differences in brain structure.”
In other words, if a pair of identical twins is separated at birth, and one grows up in a Mormon family in Utah, and the other in a secular liberal family in Boston, each will probably adopt the attitudes and beliefs of their respective cultures.
But if his insula is on the small side, the Utah-raised one may feel out of sync with the people around him. This may lead him to become apathetic or apolitical—or, perhaps, to switch sides in young adulthood. If your kid decides to break with the family orthodoxy during or shortly after college, chances are his brain had long been nudging him to do so.
(Stay tuned for more on this topic: Lewis and his colleagues are currently conducting studies of attitudes among twins, including prejudice, religiosity, and authoritarianism.)
In an election year during a period of intense political polarization, these findings—if interpreted in a charitable way—could conceivably put a damper on demonization.
“People on the left and right—their brains are literally different,” Haidt notes. “Now do you believe (your opponents) are not just being obtuse? They’re actually calling it as they see it; they just see things differently.
“My guess, though,” he added, “is that each side will look at this and say the other side has brain damage.”