House Democrats and Republicans didn’t agree on much during the public hearings held as part of the impeachment inquiry into President Donald Trump. But both sides and the witnesses did utter the same pair of words every day of the hearings — 50 times overall. And those two words were “conspiracy theory.”

From CrowdStrike to speculation about Jeffrey Epstein’s death, conspiracy theories have become central talking points in American politics and culture — or at least that’s how it feels on the internet.

It’s common for people to believe in conspiracy theories. So common that recent work suggests everyone believes in at least one conspiracy theory. But being common does not necessarily mean these unfounded assertions are becoming more widely accepted.

“Journalists are saying that ‘now is the time of conspiracy theory.’ But they’ve said that almost every year since the 1960s,” said Joe Uscinski, a political scientist at the University of Miami who studies the origins and behaviors associated with conspiracy theories. “At no time do they present any systematic evidence to back that up.”

Five years ago, Uscinski and political scientist Joseph Parent reviewed more than 100,000 letters to the editor received by The New York Times and the Chicago Tribune between 1890 and 2010 — arguably the only long-term survey of conspiratorial beliefs. Aside from spikes in the 1890s — due to distrust in rising industrialization — and during the Red Scare in the 1950s, public belief in conspiracy theories remained stable. Picking up where the survey leaves off, polls show this flat trend has continued over the last decade.

“Based on the research that I’ve done and that other psychologists have done, conspiracy thinking seems to be a fairly stable predisposition,” said Robert Brotherton, a psychologist and lecturer at Barnard College, who studies conspiracy theories. He and other cognitive scientists describe being conspiracy minded — or conspiracism — to be like any other personality trait, with some people more predisposed and others less so.

Polling over the last decade has consistently found that most Americans — approximately 55 percent — believe in popular and unfounded conspiracy theories, such as the idea that the Iraq War was a globalist plot to control oil reserves, or the suggestion that airplane “chemtrails” are used for mind control.

So why does it feel like we talk about these theories more? It’s not a change that originates from our own susceptibility to conspiracy theories, but appears to be the news media’s growing attention on them, as exemplified by this passage from Uscinski’s 2018 book “Conspiracy Theories and the People Who Believe Them”:

In November 2017, The New York Times published an article with the term conspiracy theories in it nearly every day. For comparison, the Times published zero such articles that same month, forty years prior.

Part of this uptick in news coverage is due to political leaders who are so often invoking conspiracy theories in their rhetoric, Uscinski said. Politicians mentioning conspiracy theories — like QAnon, “the system is rigged,” “Russian assets” or the “deep state” — seem to break the threshold, and news outlets feel compelled to explain what they are or explore their validity.

“Conspiracy theories are being overplayed” in the news, Brotherton said. “Conspiracy theories can affect some people’s beliefs and choices,” such as with the El Paso shooter or with anti-vaxxers. But for the most part, they don’t.

Yet the news media’s fascination with conspiracy theories and its regular attempts at debunking them through fact checking may reinforce misplaced beliefs and perpetuate public trust in conspiracy theories. That’s because of how the human brain works and the way messages now echo across the internet and social media.

But done correctly, debunking can combat people’s faith in false conspiracy theories.

That’s why, before you join family members around the holiday table and try to explain why 9/11 wasn’t “an inside job” while grabbing an extra helping of cranberry sauce, you should read PBS NewsHour’s neuroscience-backed guide to approaching your loved ones’ conspiratorial beliefs.

Defining the conspiracy theory

People — even smart and savvy ones — mix up conspiracy theories, falsehoods and myths. Here is the key difference: A conspiracy — and by extension a conspiracy theory — must involve a group of people conducting secret deeds that disadvantage or infringe on the rights of others.

Conspiracy theories lack public, objective and verifiable proof.

For instance, linking vaccines to autism is a false belief. If you think vaccines cause autism because health officials deem it so, then you believe in a conspiracy theory. Another falsehood is that fluoride is harmful to your body. A conspiracy theory is that fluoride is harmful to your body and a form of mind control perpetuated by government officials.

The central component of conspiracy theories — the difference between them and real conspiracies — is proof. Conspiracy theories lack public, objective and verifiable proof.

This may be hard to fathom, but conspiracy theories are essential to a well-functioning society. Investigative journalism thrives on exposing conspiracies — or what experts call the process of epistemology. That applies to the Panama Papers, the Flint water crisis, the Edward Snowden revelations about domestic surveillance, the CIA’s role in the cocaine epidemic in the 1980s, or President Richard Nixon’s Watergate scandal. Many of those events started as conspiracy theories until their underlying evidence was discovered and made public.

Conspiracy rhetoric is a fundamental strategic tool employed in politics across the partisan spectrum. An opposition party — typically the party in the minority — tends to push the concept that the people in charge are working against the interests of the populace.

“It’s certainly strategic to say that you are the victim of a conspiracy, that there is a witch hunt out to get you. Because it sort of throws those accusations into a negative light,” Uscinski said. “It turns the attention away from you trying to defend yourself, to finding the truth. Now the accuser has to defend themselves.”

News outlets sometimes cite Republicans as being more prone to conspiracy theory beliefs. Studies find the right and left are actually equally susceptible, but their reasons for adopting such thinking are different. For example, studies show Republicans are more likely than Democrats to believe a conspiracy theory if it fits their ideology.

The problem is not that these conspiracy theories exists, but rather that people blindly trust that these assertions are true without evidence.

6 reasons people trust conspiracy theories

Correcting a misconception — a falsehood that someone believes is accurate — “is really hard to do,” even if the message isn’t as complex as a conspiracy theory, said Nadia Brashier, a cognitive scientist at Harvard University who studies the cognitive shortcuts people use to evaluate the truth.

To understand why people believe in conspiracy theories, you need to ask yourself how the human brain decides any piece of information is true.

To understand why people believe in conspiracy theories, you need to ask yourself how the human brain decides any piece of information is true.

There are three essential keys behind how our brains judge a piece of information as being true, according to a comprehensive review of the current thinking in this field, co-published by Brashier and Duke University cognitive psychologist Elizabeth Marsh in September. Those keys are base rates, emotional feelings and consistency.

The base rate refers to the research-backed tendency of humans to inherently think that what they encounter is true, no matter the circumstance. We are mentally biased toward wanting to believe what we encounter is real. Humans are naturally trustful, rather than distrustful.

Brashier said that’s because most of what we confront in our day-to-day lives involves events that are objectively true.

“It’s not the case that most of the images we see are ‘Photoshopped’ or even that most of the headlines we encounter are fake,” Brashier said. “Most of what people tell us interpersonally is true. There might be lies mixed in, but it’s not the majority of what we hear.”

The second key to judging truth — emotional attachment — helps solidify those misconceptions. Our emotions evolved over millions of years as a survival mechanism. Being able to associate positive or negative feelings about certain colors may have served as a reminder for our primal ancestors about which foods were safe. Social emotions — like anger, gratitude and guilt — guide how we weigh our welfare versus that of others.

As a result, our emotions help craft our identities, which we defend fiercely, even when we’re wrong. Look no further than how political divisions influence perceptions of the objective truth.

The third key to judging truth is consistency — when our brains encounter the same concept or claim repeatedly, they become more likely to believe it.

As the NewsHour reported in March, political tribalism “is one of the strongest motivators for human behavior. We derive pleasure and social capital from being members of a clique, and consequently, our minds exert tremendous energy to signal our beliefs to those who might agree with us.”

The third key to judging truth is consistency — when our brains encounter the same concept or claim repeatedly, they become more likely to believe it. Brashier said that’s why social media has become such a natural habitat for perpetuating conspiracy theories.

“There’s always been false advertising or other kinds of misinformation campaigns. It just looks different now with the rise of social media,” Brashier said. “Social media makes this kind of content quickly accessible to a lot of people.”

So even if the base rate has remained steady over time — people haven’t inherently become more skeptical — it may feel like conspiracy theories are flourishing because of how they spread on social media. Just think of the echo chambers you see grow in your friend’s feeds — with people piling on misinformation post after post.

Beyond those three keys, researchers point to three more factors. People and echo chambers feed on conspiracy theories because of proportionality bias, Brotherton said. That’s the idea that the bigger an event is, the bigger an explanation we seek.

“This does seem to be a fundamental aspect of our psychology. It’s intuitively unsatisfying to think that something very small could cause something very big,” Brotherton said. “That a lone gunman could kill John F. Kennedy, the president of the United States, and change the course of history — it’s not intuitively satisfying. We want to think that there was some much bigger cause.”

In his book “Suspicious Minds: Why We Believe Conspiracy Theories,” Brotherton argues this tendency in conspiracy-theory believers is supported by a human desire to search for patterns, especially when it comes to the intentions of others.

“If you’re more inclined to think about other people’s motives, you’re probably a little bit more receptive to conspiracy thinking,” Brotherton said. But when people are faced with an ambiguous pattern (what’s harder to decipher than another person’s intentions?) they try to connect the dots.

Those six elements — base rates, emotions, consistency, proportionality bias, intentionality bias and pattern searching — help explain why people believe in conspiracy theories. Now the question is, how do you dissuade them from doing so?

A step-by-step guide to debating conspiracy theories over dinner

1. Accept that you probably won’t change their mind. If a conspiratorial belief is foundational to a person’s identity or understanding of a certain subject, it will be extremely difficult to displace. “After debunking, we often see what we call the ‘continued influence effect,’ where [that] original false belief persists,” Brashier said. That can happen even if a person knows and can recount the actual facts.

Moreover, there is a hot debate right now in cognitive science over whether repeating misinformation in order to correct it makes things worse. That’s known as the backfire effect, and there is support both for and against it.

If the backfire effect exists, then people might forget or ignore the context of a fact check and be left with a stronger belief in a conspiracy theory. Some recent research in neuroscience shows that people’s brains can store an original piece of misinformation and a correction at the same time, but the memory of the correction fades at a faster rate.

2. Be kind. That said, if you’re going to try to correct a conspiracy theorist, one important thing to keep in mind is that you don’t want to ostracize them. Ostracism actually encourages people to believe in things like superstition and conspiracy theories in the first place, Brashier said.

3. Do your homework. Correcting someone’s thinking can work if a piece of misinformation can be replaced with something concrete, Brashier said. But the need for replacement facts also explains why some popular falsehoods can be so hard to combat.

Scientists have shown repeatedly that vaccines don’t contribute to autism, but they also aren’t entirely sure what actually causes autism. “So it becomes hard to replace ‘vaccines cause autism’ with something else,” despite loads of evidence supporting vaccine safety, Brashier said.

4. Push the objective truth, whenever you can and as early as possible.

Take more time than a single dinner to make your point about the objective truth. Remember, consistency is one of the reasons people trust an idea, even if that idea includes misinformation.

“Conspiracy beliefs are hard to switch back and forth,” Uscinski said. “If somebody has a strong belief in something, you’re not going to change their belief just by giving them one piece of information or having one conversation with them.”

Brashier added the ideal scenario is preventing our friends and families from falling prey to misinformation in the first place. In news media and academic publishing, corrections seldom — if ever — reach as many people as the initial publication of a falsehood. But Brashier said we can train our friends and family to be less vulnerable to fake news.

“Taking a little more time to rethink ‘gut’ reactions improves accuracy. Some of my recent work suggests that we should ask ourselves, ‘Is this true?’ Or, ‘Does this fit with facts that I know?’” Brashier said. “This prompts people to internally fact check, by comparing a claim against facts stored in memory.”

This task may be as simple as telling your relations to seek better information, or by pointing out that most conspiracies are revealed by journalistic endeavors or legal investigations — and not in chatrooms nor on social media.