Did NASA fake the moon landing? Is the government hiding Martians in Area 51? Is global warming a hoax? The answer to these questions is, “No,” yet a committed subculture of conspiracy theorists vigorously argues the opposite.

Many scholars dismiss conspiracy theorists as paranoid and delusional. Psychological data bolster their case: people who harbor conspiracist thoughts are also more inclined to paranoid ideation and schizotypy, a mild form of schizophrenia. As conspiracy theory expert Timothy Melley of Miami University has put it, these beliefs are often dismissed as “the implausible visions of a lunatic fringe.”

Yet these antiestablishment ideas are surprisingly widely held. According to a national poll released last April by Public Policy Polling, 37 percent of Americans believe that global warming is a hoax, 21 percent think that the U.S. government is covering up evidence of the existence of space aliens and 28 percent suspect a secret elite power is plotting to take over the world. Only hours after the bombing at the Boston Marathon, people suggested, in YouTube videos and elsewhere on the Web, that the attack might have been an inside job and even that the entire event was a hoax.

With so many people ascribing to weakly supported explanations for news events, belief in conspiracy theories cannot be a mere symptom of pathology. The questioning of officialdom is critical to a functioning democracy, as the recent revelations of the National Security Agency's electronic surveillance efforts illustrate. Yet new data suggest that conspiracy theories can diminish public engagement, eroding interest in issues of great political importance. Attaining a better understanding of why these ideas persist can help us devise new ways to combat misinformation.

Bundles of Beliefs

First, a note about the term: a conspiracy theory is not, of course, a theory in the scientific sense of the word. In science, a theory is an explanation of a phenomenon that has been substantiated through experiments and testing and has become accepted by most experts in the relevant field—the theory of relativity, say, or the theory of evolution. Conspiracy theorists propose, without having collected rigorous data to support their case, that powerful people or groups are secretly plotting to accomplish some sinister goal.

One consistent finding in research on conspiracism is that those who lean toward one such idiosyncratic explanation are also likely to espouse others. This observation supports the hypothesis, originally made in 1994 by sociologist Ted Goertzel of Rutgers University, that any one conspiratorial belief serves as fodder for further fringe thinking. Once a person has decided that officialdom is deceptive in one case, other disturbing world events may appear to have similarly hushed-up origins.

A case in point is the commentary on the Boston bombings by Alex Jones, an outspoken conspiracy theorist. In discussing the attacks on the marathon, he reminded his audience that two of the hijacked planes on 9/11 had flown out of Boston. Further, he suggested the bombing could be a response to the sudden drop in the price of gold or part of a government plot to expand the Transportation Security Administration's jurisdiction to include sporting events. He not only suspects intrigue in numerous incidents but also draws connections among them.

His willingness to entertain orthogonal explanations for the tragedy in Boston illustrates another facet of conspiracist thinking: a person can end up espousing contradictory beliefs. In a 2011 study psychologists Michael J. Wood, Karen M. Douglas and Robbie M. Sutton of the University of Kent in England asked college students to rate on a scale of 1 to 7 how strongly they supported the official account of Osama bin Laden's death in a military raid. People who doubted the government's report and thought instead that bin Laden was already dead at the time of the raid were, surprisingly, also more likely than others to claim that he is still alive. An analysis of opinions on the death of Princess Diana yielded a similar logical conflict: believing that she faked her own death was significantly correlated with a suspicion that Dodi Fayed's business enemies had plotted to murder the pair.

The study's analysis concluded that people do not tend to believe in a conspiracy theory because of the specifics of a scheme but rather because they possess higher-order beliefs that support conspiracist thinking in general. A strong distrust of authority would be one such overarching ideological lens. In a belief system in which authorities are fundamentally untrustworthy, alternative—even outlandish and contradictory—explanations for troubling events can seem plausible, as long as they are consistent with a skepticism toward the powers that be.

Suspicions of Science

It might be easy enough to dismiss those who claim that the Federal Bureau of Investigation lied about JFK's assassination or that Roswell, N.M., once hosted extraterrestrial visitors. Yet the deep mistrust of authority that such people harbor also extends to the realm of science. When more than a third of the population doubts the veracity of climate scientists' conclusions, as the Public Policy Polling numbers showed, the repercussions for society can be grave. In a paper published last May, psychologist Stephan Lewandowsky of the University of Western Australia and his colleagues investigated the relation between acceptance of science and conspiracist thinking patterns. They recruited their participants from climate blogs and focused their research on the belief systems of this subpopulation. Their results suggest that buying into multiple conspiracy theories predicts the rejection of important scientific conclusions, not only about climate science but also about such well-established facts as that smoking can cause lung cancer and that HIV leads to AIDS.

In addition to sowing doubts about scientific principles, belief in conspiracy theories can lead individuals to become disengaged from topics of social and political importance. In a 2013 publication Douglas and University of Kent graduate student Daniel Jolley presented statements to their study participants that supported various conspiracy theories, including one on climate skepticism. They found that people who received information affirming the idea that global warming is a hoax were less willing to engage politically and to implement behavioral changes, such as reducing their carbon footprint.

This result is alarming because it suggests that even cursory defenses of conspiracy theories can sow mistrust and divert attention from critical scientific, political and social issues. Highly visible books such as Oklahoma senator James Inhofe's recent The Greatest Hoax: How the Global Warming Conspiracy Threatens Your Future may subtly erode public support for interventions that would slow climate change—even without being read. Indeed, conspiracy theories are fiendishly difficult to unseat because any effort to rebut them has the unfortunate side effect of legitimizing them at the same time. The solution may simply be to disseminate rigorous scientific evidence as widely as possible in the hope that eventually the public becomes less susceptible to implausible worldviews.

Philosopher Karl Popper argued that the fallacy of conspiracy theories lies in their tendency to describe striking events as planned, thereby grossly underestimating the random nature and unintended consequences of many political and social actions. Popper was describing a cognitive bias that psychologists now commonly refer to as the fundamental attribution error: the habit of overestimating the intentionality behind the actions of others.

A likely function of this cognitive bias is to help people make sense of the world by offering simple explanations for complex events. A number of studies have shown that belief in conspiracy theories is associated with feelings of powerlessness and uncertainty. For example, a large 2008 study by Jennifer Whitson of the University of Texas at Austin and Adam Galinsky of Northwestern University showed that participants who lacked control were more likely to perceive illusory patterns, including conspiracies. The authors note that observing patterns where there are none fills a need for structure and organization. In other words, adopting conspiracy beliefs recasts the world as a more predictable place. A tangible enemy absorbs the blame for problems that otherwise may seem too abstract.

A good example is climate change. A 2013 analysis of peer-reviewed literature on the topic estimated the scientific consensus at 97 percent in favor of the view that anthropogenic global warming is occurring. Of course, coping with the implications of climate change may entail tremendous upheaval. Discounting the entire phenomenon as a hoax is much more convenient psychologically than making the difficult trade-offs that abating it would require. Yet as Al Gore famously pointed out, the truth is not always convenient.