Laugh and the whole world laughs with you -- Why the brain just can't help itself

The research team played a series sounds to volunteers whilst measuring their brain's response using an fMRI scanner. Some of the sounds were positive, such as laughter or triumph, whilst others were unpleasant, such as screaming or retching. All of the sounds triggered a response in the volunteer's brain in the premotor cortical region, which prepares the muscles in the face to respond accordingly, though the response was greater for positive sounds, suggesting that these were more contagious than negative sounds. The researchers believe this explains why we respond to laughter or cheering with an involuntary smile.

"We usually encounter positive emotions, such as laughter or cheering, in group situations, whether watching a comedy programme with family or a football game with friends," says Dr Scott. "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 in a group."

So, if you want Christmas with the extended family to go swimmingly, maybe you should switch off Eastenders and dig out your Only Fools and Horses DVDs.