Amidst the grief, shock and confusion that followed the Boston marathon bombings last month, efforts to explain the senseless act inevitably led to theories of conspiracy and suspicious intrigue.
The bombers themselves may have been acting against what they saw as a conspiracy. Even the mother of the two brothers who planted the bomb declared the innocence of her sons, accusing the United States government of conspiring to kill her eldest.
What is it that motivates people to latch on to conspiracy theories, often in spite of evidence to the contrary?
In some ways, it may be inherent in human nature to invest in certain beliefs at all costs, experts said, whether it's about the health consequences of vaccines or the death of John F. Kennedy. Several basic psychological processes are at work.
For one thing, people feel better if they think they're right, said Gary Marcus, a cognitive psychologist at New York University who wrote about conspiracy theorists for The New Yorker. In a phenomenon called "motivated reasoning," it's also common for people to both notice and seek out details that support their views and to reject evidence that might contradict what they want to believe.