Scott LaFee, Contributor

Laughter really is contagious, but in a good way. Indeed, British researchers say it may have evolved as a way for individuals to get along in groups.

Scientists at University College London (UCL) and Imperial College have found that positive sounds like laughter or a triumphant 'woo hoo' trigger responses in the same part of the listener's brain that also prepares facial muscles to smile.

"We've known for some time now that when we are talking to someone, we often mirror their behaviour, copying the words they use and mimicking their gestures," said Sophie Scott, a senior research fellow at UCL's Institute of Cognitive Neuroscience in the United States. "Now we've shown that the same appears to apply to laughter, too - at least at the level of the brain."

Researchers played a series of sounds to volunteers hooked up to brain scanners. The sounds ranged from laughter and giggling to screams and retching. All of the sounds spurred activity in the brain's premotor cortical region, which prepares facial muscles to respond accordingly, but positive sounds evoked a stronger response.

This is why, researchers suggest, people respond to laughter or cheering with an involuntary smile.

"We usually encounter positive emotions, such as laughter or cheering, in group situations," Scott said. "This response in the brain, automatically priming us to smile or laugh, provides a way of mirroring the behaviour of others, something which helps us interact socially. It could play an important role in building strong bonds between individuals and groups."

Relax those facial muscles

Get this joke?

Two babies were born on the same day at the same hospital. They lay there and looked at each other. Their families came and took them away. Eighty years later, by a bizarre coincidence, they lay in the same hospital, on their deathbeds, next to each other.

One of them looked at the other and said, "So, what did you think?"

Stories for the waiting room

In rural England and the backwoods of early America, it was believed that a child could be cured of whooping cough by riding on the back of a bear. Another cure, according to English folk wisdom, was eating bread and butter provided by a married couple named John and Joan.

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