You're just trying to be a good friend when you tell an angry pal to "let it out" by punching a pillow or slamming a door. But this advice is more harmful than helpful.
"Expressing anger actually increases aggression," says Brad Bushman, Ph.D. The Iowa State University psychologist and colleagues asked subjects to pen an essay, then inspired their ire by handing it back with a brutal critique. Next, the essay writers were asked to deliver noise bursts to either the person who'd insulted their paper or an innocent bystander. Subjects could decide how long and loud the annoying sounds would be. Miffed participants who hit a punching bag before administering the sounds were twice as cruel in their choice of noise length and volume as those who just sat quietly before performing the task. Furthermore, "they were aggressive toward both types of people," said Bushman, "and that's scary."
The finding is most worrisome, he says, because the media and pop psychologists promote the idea that "venting" is useful. We're easily influenced by these messages: subjects who read an article on the benefits of catharsis before punching the bag were much more likely to want to box than others.