We knew this, didn't we? Still, it's good to know that the scientists have established it. Happy people make the people around them happier. So it's socially responsible to be as happy as we can then. No more moaning about Pollyanna. She increases our own prospects of happiness far more than we contribute by our scepticism and self-styled realism.
Happy Advent, one and all (though apparently the contagious effect only works with people who live really close by, so forget those cheery cyber-friends, and spend some time with some real happy people nearby!)