WASHINGTON (AP) — Conspiracy theories have a long history.

Humans have always speculated about secret motives and plots as a way to understand their world and avoid danger.

These days, however, conspiracy theories and those who believe them seem to be playing an outsize role in politics and culture.

Republican Donald Trump has amplified conspiracy theories about climate change, elections, voting and crime, and has expressed support for the QAnon conspiracy theory. His lies about the 2020 election he lost to Democrat Joe Biden spurred the attack on the U.S. Capitol on Jan. 6, 2021, an event that quickly spun off its own conspiracy theories.

On the left, Robert F. Kennedy Jr. has exploited conspiracy theories about vaccines to wage his own campaign for the presidency this year.

Conspiracy theories have also proven lucrative for those cashing in on unfounded medical claims, investment proposals or fake news websites.

The Associated Press has examined the history of conspiracy theories in the United States.

Interviews with experts on technology, psychology and politics give insight into why people choose to believe and spread conspiracy theories, and how those beliefs are affecting our mental health, our politics and our society.

A look at some of the biggest takeaways from the investigation:

A LONG HISTORY

Conspiracy theories exposed social tensions long before the American Revolution and the birth of U.S. democracy.

Just as now, early conspiracy theories reflected popular worries of the day. In the years immediately after the American Revolution, rumors and hoaxes circulated about dark plots by the Illuminati and Freemasons, suggesting those secret organizations wanted to control the republic.

Likewise, the conspiracy theories of the modern age often reflect uncertainties about technology, immigration and government overreach. Stories about UFO coverups, microchips in vaccines or the attacks of Sept. 11, 2001, being an inside job are examples.

While the specific claims in many of these tales can be debunked, the stories reflect anxieties shared by millions of people.

“We are the stories we tell ourselves,” said John Llewellyn, a professor at Wake Forest University who studies conspiracy theories and why people believe what they believe.

WHY PEOPLE BELIEVE

Humans thirst for information that can help them protect themselves and help them make better decisions for the future. This information, along with personal experiences, upbringing and cultural perspectives, creates a view of the world that helps people understand big events and forces in their lives.

Disasters, elections, wars and even the outcomes of sporting events can shake our perspective, and make us look for explanations. Sometimes that means accepting the facts. But sometimes it can be easier to embrace an alternative explanation.

Conspiracy theories can act as a shortcut to understanding. They fill in the gaps of understanding with speculation that often reflects more about the believer’s inner beliefs than the events themselves. Conspiracy theories suggesting vaccinations are being used to implant microchips in people, for instance, reflect concerns about technology, medicine and government power.

With the internet, false claims and conspiracy theories can travel further and faster than ever. Social media algorithms prioritize content that elicits strong emotions, like anger and fear.

FACING THE DEMONS

The AP interviewed dozens of current and former conspiracy theory believers to understand what led them to believe. They consistently said conspiracy theories offered them a sense of power and control in a world that can seem random and chaotic.

“The pieces did not fit,” said Melissa Sell, a conspiracy theorist from Pennsylvania who began doubting the official narrative of history after the Sandy Hook Elementary School shooting in Connecticut 2012.

They spoke of growing distrust of democratic institutions and the media, and a gnawing feeling they were being lied to. The world of online conspiracy theories offered answers, and a built-in community of like-minded people.

“I was suicidal before I got into conspiracy theories,” said Antonio Perez, a Hawaii man who became obsessed with Sept. 11 conspiracy theories and QAnon until he decided that they were interfering with his life. But when he first found other online conspiracy theorists, he was ecstatic. “It’s like: My God, I’ve finally found my people!”

TURNING IDEAS INTO ACTION

Polls show nearly half of Americans believe a conspiracy theory and that those beliefs are almost always harmless. But when fringe views interfere with a person’s job or relationships, they can lead to social isolation. And when people put their conspiracy theory beliefs into action, it can lead to violence.

In recent years, conspiracy theorists have tried to stop vaccine clinics, they’ve attacked election officials and they’ve committed murders that they say were motivated by their beliefs. The Jan. 6 riot is perhaps the most notable example of how conspiracy theories can lead to violence: The thousands of people who stormed the Capitol and fought with police were motivated by Trump’s election lies.

Such rapidly spreading disinformation fuels extremist groups and encourages distrust — a particular concern during a year of big elections in the U.S. and other nations. Russia, China, Iran and other U.S. adversaries have worked to amplify conspiracy theories as a way to destabilize democracy further. Artificial intelligence’s ability to rapidly create lifelike video and audio only increases the challenge.

“I think the post-truth world may be a lot closer than we’d like to believe,” said A.J. Nash, vice president for intelligence at ZeroFox, a cybersecurity firm that tracks disinformation. “What happens when no one believes anything anymore?”

PROFITING OFF BELIEF

As long as there have been conspiracy theories, people have tried to make a buck off of them. A century or more ago, peddlers went from town to town selling tonics and pills that they said could cure just about any problem. Nowadays, sales take place online. Business is booming.

There are supplements that claim to reverse aging, bogus treatments for COVID-19, T-shirts, investment scams claiming a new financial order is just around the corner.

The AP took a close look at conspiracy theories involving medbeds, which are futuristic-looking devices that believers think can reverse aging and cure a long list of illnesses. According to claims circulating online, the U.S. military is hiding the technology from the public but that Trump, if he wins another term as president, will make them available for free. For people desperate to find help with a medical condition, the claims can be too tempting to ignore.

“There have always been hucksters selling medical cures, but I do feel like it’s accelerating,” said Timothy Caulfield, a health policy and law professor at the University of Alberta who studies medical ethics and fraud. “There are some forces driving that: obviously the internet and social media, and distrust of traditional medicine, traditional science. Conspiracy theories are creating and feeding this distrust.”