The principle behind Chekhov's Gun goes something like this: If there's a rifle in the first act, it better be fired by the third. The great Russian writer, of course, was talking about eliminating unnecessary elements of story plots, but it seems that we Americans have been taking his words all too literally-and to the grave. According to a University of Pennsylvania research team led by Charles Branas (not to be confused with Charles Bronson, pictured), people who carry guns are far more likely to get shot and killed than people who are unarmed. From New Scientist:Overall, Branas's study found that people who carried guns were 4.5 times as likely to be shot and 4.2 times as likely to get killed compared with unarmed citizens. When the team looked at shootings in which victims had a chance to defend themselves, their odds of getting shot were even higher.So is carrying a gun an automatic death wish? Not exactly. Branas did point out that the study should not necessarily be taken as fodder for gun control advocacy, nor should it strike fear in the hearts of Second Amendment supporters. To paraphrase him, the study should function simply as the beginning of a conversation.Photo (cc) by Flickr user Hryck.