People who suspect a conspiracy was at work in the 9/11 terror attacks, or in the way the U.S. government responded to it, are not crazy, says one Canadian psychology professor working in Norway. Floyd Rudmin, with the University of Tromso, says those labelled "conspiracy theorists" with regard to 9/11, the John F. Kennedy assassination or any number of other dramatic events have good reason to doubt the explanations given to the public by authorities.

"Some people say there are no conspiracies and that all conspiracy theories are nonsense," he says. "That simply is not true. Humans do conspire."

Rudmin says he has no specific explanations for how 9/11 happened, but he does not believe the official version of events.