If you want to meet happy, fun people online all you have to do is smile. Putting a picture of yourself smiling on a social networking site (Facebook, Bebo, etc.) will attract people who are fun!

Happy people cluster together, the research suggests. And the opposite also seems to be true — so if you are miserable, you are more likely to have miserable friends.

The effect holds in both the real and virtual worlds. People who put smiling photos on their profiles for social networking sites such as Facebook tend to link to one another. Frowners do likewise.

But it’s not just direct contact that counts. The link is significant to three degrees of separation — that is, your own emotional state is connected to that of your friends’ friends’ friends.

“Your happiness depends on the happiness of individuals beyond your own social horizon,” says sociologist Nicholas Christakis of Harvard University in Cambridge, who carried out the study. “You can understand happiness by studying individuals, but that only gets you so far. There’s more to be learned by studying the group.”