For some people, the need to believe in conspiracy theories is so great that they're prepared to believe two completely contradictory ideas at the same time.
A team at the University of Kent says the phenomenon derives from a compulsive mistrust of authority.
"Any conspiracy theory that stands in opposition to the official narrative will gain some degree of endorsement from someone who holds a conpiracist worldview," say the university's Michael Wood, Karen Douglas and Robbie Sutton.
The researchers asked 137 college students about the death of Princess Diana - and found that the more people thought there "was an official campaign by the intelligence service to assassinate Diana," the more they also believed that "Diana faked her own death to retreat into isolation."
Similarly, they asked 102 college students about the death of Osama bin Laden. And people who believed that "when the raid took place, OBL was already dead," were significantly more likely to also believe that "OBL is still alive."
"Since bin Laden is not Schrödinger's cat, he must either be alive or dead," they point out.
The reason, they say, is that both theories, while utterly contradictory, are consistent with the belief that the "actions of the Obama administration indicate that they are hiding some important or damaging piece of information about the raid".
For some people, in other words, conspiracy belief is so powerful that it will lead to belief in completely inconsistent ideas.
"For conspiracy theorists, those in power are seen as deceptive - even malevolent - and so any official explanation is at a disadvantage, and any alternative explanation is more credible from the start," say the authors.
When distrust comes into play, careful reasoning can disappear.
"Believing Osama is still alive," the authors write, "is no obstacle to believing that he has been dead for years."