If you see two people laughing at a joke you didn’t hear, chances are you will smile anyway–even if you don’t realize it.
According to a new study, laughter truly is contagious: the brain responds to the sound of laughter and preps the muscles in the face to join in the mirth.
“It seems that it’s absolutely true that ‘laugh and the whole world laughs with you,” said Sophie Scott, a neuroscientist at the University College London. “We’ve known for some time that when we are talking to someone, we often mirror their behavior, copying the words they use and mimicking their gestures. Now we’ve shown that the same appears to apply to laughter, too–at least at the level of the brain.”