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.

This doubled response in the part of the brain that prompts muscles to react in kind suggested that people were essentially helpless to control the impulse to smile or laugh when they heard pleasant sounds.

So, here are a couple of helplessness tests. The first, an audiovisual one of a baby laughing (for those averse to children, his laugh has an eerily adult timbre), and the second, a purely audio one of BBC cricket commentators Brian Johnston and Jonathan Agnew getting the giggles about Ian Botham failing to get his leg over ... the wicket.