So sharp are partisan divisions these days that it can seem as if people are experiencing entirely different realities. Maybe they actually are, according to Leor Zmigrod, a neuroscientist and political psychologist at Cambridge University. In a new book, “The Ideological Brain: The Radical Science of Flexible Thinking,” Dr. Zmigrod explores the emerging evidence that brain physiology and biology help explain not just why people are prone to ideology but how they perceive and share information.

This conversation has been edited for clarity and brevity.

What is ideology?

It’s a narrative about how the world works and how it should work. This potentially could be the social world or the natural world. But it’s not just a story: It has really rigid prescriptions for how we should think, how we should act, how we should interact with other people. An ideology condemns any deviation from its prescribed rules.

You write that rigid thinking can be tempting. Why is that?

Ideologies satisfy the need to try to understand the world, to explain it. And they satisfy our need for connection, for community, for just a sense that we belong to something.

There’s also a resource question. Exploring the world is really cognitively expensive, and just exploiting known patterns and rules can seem to be the most efficient strategy. Also, many people argue — and many ideologies will try to tell you — that adhering to rules is the only good way to live and to live morally.

I actually come at it from a different perspective: Ideologies numb our direct experience of the world. They narrow our capacity to adapt to the world, to understand evidence, to distinguish between credible evidence and not credible evidence. Ideologies are rarely, if ever, good.

Q: In the book, you describe research showing that ideological thinkers can be less reliable narrators. Can you explain?

Remarkably, we can observe this effect in children. In the 1940s, Else Frenkel-Brunswik, a psychologist at the University of California, Berkeley, interviewed hundreds of children and tested their levels of prejudice and authoritarianism, like whether they championed conformity and obedience or play and imagination. When children were told a story about new pupils at a fictional school and asked to recount the story later, there were significant differences in what the most prejudiced children remembered, as opposed to the most liberal children.

Liberal children tended to recall more accurately the ratio of desirable and undesirable traits in the characters of the story; their memories possessed greater fidelity to the story as it was originally told. In contrast, children who scored highly on prejudice strayed from the story; they highlighted or invented undesirable traits for the characters from ethnic minority backgrounds.

So, the memories of the most ideologically-minded children incorporated fictions that confirmed their pre-existing biases. At the same time, there was also a tendency to occasionally parrot single phrases and details, rigidly mimicking the storyteller.

So by “liberal” you mean flexible in thought rather than politically liberal, yes?

Right. The work with children is about prejudice rather than conservatism. Ideologues are strong partisans either to the left or right. Psychological rigidity is linked to ideological extremity regardless of the mission of the ideology.

Are people who are prone to ideology taking in less information? Are they processing it differently?

The people most prone to ideological thinking tend to resist change or nuance of any kind. We can test this with visual and linguistic puzzles. For instance, in one test, we ask them to sort playing cards by various rules, like suit or color. But suddenly they apply the rule and it doesn’t work. That’s because, unbeknownst to them, we changed the rule.

The people who tend to resist ideological thinking are adaptable, and so when there’s evidence the rules have changed, they change their behavior. Ideological thinkers, when they encounter the change, they resist it. They try to apply the old rule even though it doesn’t work anymore.

In one study you conducted, you found that ideologues and nonideologues appear to have fundamental differences in their brains’ reward circuitry. Can you describe your findings?

In my experiments I’ve found that the most rigid thinkers have genetic dispositions related to how dopamine is distributed in their brains.

Rigid thinkers tend to have lower levels of dopamine in their prefrontal cortex and higher levels of dopamine in their striatum, a key midbrain structure in our reward system that controls our rapid instincts. So our psychological vulnerabilities to rigid ideologies may be grounded in biological differences.

In fact, we find that people with different ideologies have differences in the physical structure and function of their brains. This is especially pronounced in brain networks responsible for reward, emotion processing, and monitoring when we make errors.

For instance, the size of our amygdala — the almond-shaped structure that governs the processing of emotions, especially negatively tinged emotions such as fear, anger, disgust, danger and threat — is linked to whether we hold more conservative ideologies that justify traditions and the status quo.

What do you make of this?

Some scientists have interpreted these findings as reflecting a natural affinity between the function of the amygdala and the function of conservative ideologies. Both revolve around vigilant reactions to threats and the fear of being overpowered.

But why is the amygdala larger in conservatives? Do people with a larger amygdala gravitate toward more conservative ideologies because their amygdala is already structured in a way that is more receptive to the negative emotions that conservatism elicits? Or can immersion in a certain ideology alter our emotional biochemistry in a way that leads to structural brain changes?

The ambiguity around these results reflects a chicken-and-egg problem: Do our brains determine our politics, or can ideologies change our brains?

If we’re wired a certain way, can we change?

You have agency to choose how passionately you adopt these ideologies or what you reject or what you don’t.

I think we all can shift in terms of our flexibility. It’s obviously harder for people who have genetic or biological vulnerabilities toward rigid thinking, but that doesn’t mean that it’s predetermined or impossible to change.