Laugh and the world laughs with you

New research shows that laughter is, in fact, contagious.

It's not just an act of mimicry, like yawning in reaction to someone else's gaping mouth, or empathy, like feeling pained when hearing someone cry.

Reporting in the Journal of Neuroscience, researchers found that the brain's response to pleasant sounds such as laughter was twice as big as it was for unpleasant ones, such as ... mmm, retching.