Joseph E. Uscinski is an associate professor of political science at the University of Miami. He is a co-author, along with Joseph M. Parent, of “American Conspiracy Theories.”

Supreme Court Justice Antonin Scalia at an event at the Federalist Society in New York. (Darren Ornitz/Reuters)

Supreme Court Justice Antonin Scalia died just days ago, but already conspiracy theories about his death abound. Radio talk-show host Alex Jones suggested that a pillow found near Scalia’s head might indicate that he’d been suffocated. Some retired detectives said the lack of an autopsy was evidence of a cover-up. One website (the aptly named Trunews) wondered whether the CIA used heart-attack-inducing drugs to kill the justice. Even Donald Trump joined the fray, calling the death “pretty unusual.”

For those who don’t believe that the justice was murdered — Scalia, at 79, had passed average life expectancy — it can be disconcerting to watch a large swath of the public fall prey to hysteria and paranoia. After all, we live in a democracy. If a substantial portion of Americans operate in a conspiracy-fueled delirium, how can we make sound decisions, choose thoughtful leaders and support rational policies?

Those concerns motivated psychologists and social scientists like me to try to better understand why people believe conspiracy theories and what the consequences are. In the past decade, scientists have conducted hundreds of opinion polls and laboratory experiments on the subject, leading to the publication of dozens of books and scholarly articles. Based on this emerging body of research, the explosion of Scalia assassination theories is probably two-fold. First, some people are, by their nature, inclined toward conspiratorial logic. Second, partisans tend to view their side as virtuous and the opposition as ignorant, wrong-headed, corrupt and perhaps evil. Increasingly partisan times, like these, stir the pot even more.

Recently, psychologists began measuring people’s predisposition to believe conspiracy theories. Using polling and questionnaires, scientists developed a list of questions about political control and secrecy. The surveys were designed to tap respondents’ underlying views of how the world works, rather than their thoughts about specific conspiracy theories.

Through these experiments, researchers found that conspiratorial thinking falls on a spectrum. Some people are very inclined toward conspiracy theories, seeing them lurking behind every corner, no matter the facts. People on the opposite end of the spectrum are unlikely to accept conspiratorial beliefs, even when mounting evidence suggests that something is afoot. The folks on this extreme might be thought of as naive; conspiracy theorists often refer to them as “sheeple.” Most people are somewhere in the middle — they believe in some conspiracy theories but reject most.

For example, in one national poll, respondents were given a list of nine groups to choose from that included “corporations and the rich,” “communists and socialists,” “the government” and “foreign countries.” Participants were asked to select any groups they believed were working in secret against the rest of us. The respondents who scored lowest on the spectrum of conspiracy thinking chose an average of about 11/2 groups. Respondents with stronger predispositions toward such thinking picked more. Those at the highest levels of conspiratorial thinking choose about 41/2 groups.

Given this, it’s not surprising that some people thought of conspiratorial explanations — corruption! assassination! intrigue! — as soon as they heard of Scalia’s passing. It’s also unsurprising that most national news coverage of these conspiracy theories has been to debunk them.

Partisanship also drives conspiracy theories. Partisans often view politics as a Manichean struggle, with their party as good and the other as evil. This leads them to believe that if something bad happens, the other side caused it. This plays out over and over again in our national discourse. For example, after the shooting in San Bernardino, Calif., last year, Republicans criticized what they called Obama’s weak stance on terrorism; Democrats blamed the GOP for what they consider lax gun laws. For the conspiratorially minded, it’s a hop, skip and a jump to accusations of scheming: Some on the right suggested that the Obama administration orchestrated the San Bernardino attack so that afterward, it could take away gun rights. Some on the left continue to suggest that the George W. Bush administration was either complicit or directly involved in the 9/11 attacks.

Social scientists such as Alfred Moore, Joseph M. Parent and myself have used polls to show that members of both parties harbor conspiratorial thinking, and in equal amounts. But at any given time, the balance of domestic power makes it look like only one side belongs to the paranoid fringe. That’s because the theories that gain traction tend to come from those accusing the people in power of wrongdoing. Since President Obama’s election, most of the prominent conspiracy theories have originated with Republicans. They have accused the president of faking his birth certificate, blowing up the Deepwater Horizon oil rig, killing moviegoers in Aurora, Colo., and faking the slaughtering of children at Sandy Hook Elementary.

But go back a few years, and we observe the opposite: Democrats sounding the alarms with 9/11 truther theories and obsessions with the Iraq war, Halliburton, Dick Cheney and Blackwater.

In fact, when one party wins a presidential election, a significant portion of the other party believes the election was rigged. For example, a Fairleigh Dickinson poll shows that about 37 percent of Democrats believe that Republicans committed fraud to keep the presidency in 2004; 36 percent of Republicans believe that Democrats committed fraud to stay in the White House in 2012. The most prominent conspiracy theories accuse the biggest and most powerful actors. In other words, conspiracy theories are for losers.

Looking back in history, we see the same thing: When President Franklin Roosevelt attempted to pack the Supreme Court with like-minded justices, some Republicans declared that Roosevelt was conspiring to become a dictator.

It therefore follows that when a conservative Supreme Court justice dies in office, some Republican conspiracy theorists will immediately conclude that the Democratic president and those under his control murdered him. The urge to blame Obama is made even more potent by the fact that Scalia’s death will change the ideological balance of the court in a way that favors liberals. Republicans think they just lost control of a branch of government.

It’s hard to know how the United States ranks alongside other countries in terms of its penchant for conspiracy theories, since there are no systematic comparisons. But my research has led me to believe that Western Europeans and Americans are, for the most part, anti-conspiratorial. Conspiracy theories certainly exist, but people mostly believe in and trust the American system and its institutions. One study that tracked levels of conspiricism using letters to the editor in prominent newspapers shows that conspiratorial talk has decreased in the past several decades. In other regions, like post-communist Eastern Europe, conspiracy theories abound. This may be because institutions in those countries are less transparent.

There have been millions of conspiracy theories. Very few convince many people; most come and go with little notice. The Scalia theories will probably make headlines for a few weeks, then disappear from our discourse.

That doesn’t mean we shouldn’t pay attention. Conspiracy theories broadcast people’s deepest fears and values. By doing this, they offer leaders a signal. In this case, Obama should see that Americans on the right are uneasy about a shift of power on the highest court. In naming a replacement, he could show empathy for those who are afraid by directly engaging with those worries and choosing a compromise nominee.

It’s worth remembering that, very occasionally, conspiracy theories turn out to be true. Just ask the two cheeky journalists at this newspaper who followed a crazy conspiracy theory and brought down a sitting president.