Donald Trump touts conspiracy theories more than most presidents in recent history, or perhaps any president ever. Trump has claimed that President Obama wiretapped his phone during the presidential campaign (a charge the FBI denied) and that several million people voted illegally in the election (also: no evidence). In the past, he’s said that climate change is a hoax perpetrated by the Chinese (it’s not).

But he’s certainly not alone in jumping to conspiracies to explain world events. Often conspiracy theories can be powerful and damaging.

Consider the agony of the family of Seth Rich, the Democratic Nationally Committee staffer who was murdered in an apparent robbery attempt over the summer. Despite zero evidence, conspiracy theorists and prominent conservative pundits have been fanning the suspicion that Rich was murdered by the Clinton campaign. “Seth’s death has been turned into a political football,” Rich’s parents wrote at the Washington Post. “Every day we wake up to new headlines, new lies, new factual errors, new people approaching us to take advantage of us and Seth’s legacy.”

The pain inflicted by conspiracy theories can be immense: To this day, parents of slain Sandy Hook children are charged with making up the whole thing (including the lives of their children), for example.

But why would people believe that these parents (who have suffered incredible loss) are lying? For that matter, why are the people who broadcast these theories — like Alex Jones — so appealing?

To find out, I called up Jan-Willem van Prooijen, a social and organizational psychologist at Vrije Universiteit Amsterdam who studies why people believe in conspiracy theories, and what personality and situational factors contribute to those beliefs.

The theories are a tool by which people can feel more in control, and find explanations in a scary and turbulent world. And yet we’re not all equally susceptible to conspiracies. In the interview that follows, van Prooijen explains why some conspiracy theories take off and why some people are more vulnerable to them, and the evolutionary theory underpinning their ubiquity.

This conversation has been edited for length and clarity.

Brian Resnick

What is a conspiracy theory?

Jan-Willem van Prooijen

A conspiracy theory is the belief that a group of people — often powerful people — collude in secret in order to make plans that are widely seen as malevolent or evil. That’s the simple definition.

Brian Resnick

What makes these theories so compelling?

Jan-Willem van Prooijen

[They’re] a tool to explain reality. We can’t always know or understand everything that happens to us. When people are uncertain about change — when they lose their jobs, or when a terrorist strike or a natural disaster has occurred — then people have a tendency to want to understand what happened, and also a tendency to assume the worst. It’s a self-protective mechanism people have. This combination of trying to make sense and assuming the worst often leads to conspiracy theories.

They’re particularly likely to flourish in times of collective uncertainty in society. Particularly after high-profile incidents that imply a sudden change in society or a sudden change in reality in a threatening way. Think 9/11, but also think of disease outbreaks [or] long-term threats like an economic crisis or climate change.

Brian Resnick

Is everyone susceptible to believing in conspiracy theories?

Jan-Willem van Prooijen

The tendency to perceive conspiracies is universal. It’s in all of us. But I also think there are individual differences in susceptibility to them. You have to realize not all conspiracy theories are irrational. Sometimes corruption does happen. It’s natural for people to be on their guard for that.

A good predictor of conspiracy theories is actual oppression. Frequently oppressed minority groups in society are more likely to believe in conspiracy theories, and one reason why they do so is because they’re trying to make sense of the actual problems they have. [Conspiracy theories are] a way of trying to understand, trying to make sense of the circumstances one finds themselves in. And the worse these actual circumstances are, the more the need people feel to come up with good explanations and the more likely people are to blame their circumstances on powerful groups.

Brian Resnick

If they’re universal across cultures, does that mean there’s an evolutionary reason to believe in conspiracy theories?

Jan-Willem van Prooijen

Actually, yes. Throughout human history, many people were victimized — and killed — by hostile coalitions. Hence, in an ancestral environment it can have been adaptive to quickly detect possibly hostile coalitions (i.e., conspiracies) before they strike, even when this often implies mistakes (i.e., false accusations of conspiracy formation).

Brian Resnick

What makes one person more susceptible to conspiracy theories than another?

Jan-Willem van Prooijen

There are a few factors that we have identified.

One of them is education level. Conspiracy theories are more likely among people who are [less] educated. But this doesn’t mean that people who are highly educated are immune.

There’s also effects of political ideology. In our research, we find the more radical a person’s politics [both left- and right-wing], the more likely they are to be conspiracy theorists.

Another is collective narcissism [a personality trait where people demand the group they belong to be admired], and people who believe their own nation and group is superior to others.

Brian Resnick

How do people start down the path of becoming a conspiracy theorist? Is there some sort of gateway drug into this world?

Jan-Willem van Prooijen

The best predictor of believing in one conspiracy theory is believing in another. Once they firmly start to believe in one specific conspiracy theory, it opens the door to many others. Because then people start thinking, “Hey, there may be a lot more going on behind the scenes that I don’t know. What else is there?”

It [becomes] a way to look at the world — to see a world full of conspiracies, big powers behind the screens pulling all the strings. And actual conspiracies [like reports of scandal on the news that are indeed real] also feed into it.

I’m not sure if it’s addicting, but it’s perpetuating. The more conspiracy theories you believe in, the more susceptible you'll become to others.

Brian Resnick

I read your recent paper looking into why education makes a person less likely to believe in conspiracy theories. I was interested to learn that the answer isn’t just, “Because smarter people don’t believe in conspiracy theories.” Can you explain the nuance there?

Jan-Willem van Prooijen

The lower educated are less able to think analytically, and therefore they believe in more simplistic theories [and conspiracy theories, while sometimes elaborate, serve to simply explain horrible things in the world]. But that’s not the whole story.

We also find people [who] are high in education experience more feelings of control over their environment, and have more feeling that they can actually change their situation if they proactively approach it. (And people who feel powerless are more likely to believe in conspiracy theories.)

So interventions that are aimed at transforming pessimism into optimism are likely to help.

Brian Resnick

How would that work? Pessimism can be hard to change.

Jan-Willem van Prooijen

There’s no cure that will make everyone an optimist. But I do think there are interventions you could implement. I do not know of a specific intervention; more generally what matters to instill optimism is to provide people with the feeling that they can make a difference and shape the future for the better. This can pertain to people’s own lives, but also to society as a whole. What characterizes pessimism is the feeling that there is a dark future ahead and there is little one can do to avoid it.

Brian Resnick

Alex Jones is a popular conspiracy theorist in the United States. A part of his appeal, I think, is that he’s kind of fun to watch. He rants and raves. You can see the blood boiling in his face.

It’s entertaining. Is that part of the appeal of conspiracy theories? That they are fun to think through?

Jan-Willem van Prooijen

That’s an excellent suggestion. It’s an alternative way at looking at reality, and in a way that can also be entertaining. Just like paranormal beliefs are entertaining. It’s a story. And a good story is fun.

There’s actually now holidays you can book called Conspira-Sea — a cruise ship where you can watch presentations by conspiracy theorists.

But conspiracy theories are not just satisfying. They are also frightening. People who strongly believe in conspiracy theories also have higher levels of anxiety. So they’re not reassuring.

Brian Resnick

Is there any reason to think belief in conspiracy theories will become more common, because of the political environment or because of communication technology? Never before has it been easier to disseminate false information.

Jan-Willem van Prooijen

I’m not sure. In a study by two political scientists from Miami, they analyzed over 100,000 letters sent to the New York Times and Washington Tribune that spanned a time period of 120 years (1890 to 2010). They did not find evidence for more conspiracy theories as society got technologically more advanced. So while I do believe modern technology is likely to have an impact (e.g., information overload, speed of dissemination), I am not sure whether it actually increases conspiracy theories.

Correction: This article originally stated Jan-Willem van Prooijen works at the University of Amsterdam. He works at Vrije Universiteit Amsterdam.