Just like real life, in virtual world too happy people attract joyful pals. That's the conclusion of a new research, which says that people who post smiley photos on social networking sites like Facebook attract happy friends.
According to the US study, which looked at the spread of happiness and depression across social networks, the level of your happiness is influenced by your social links to people you've never heard of and never met.
The research suggests that happy people cluster together. And the opposite of it also seems to be true - so if you are miserable, you are more likely to have miserable friends.
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," Nature quoted sociologist Nicholas Christakis of Harvard University in Cambridge, who carried out the study, as saying.
"You can understand happiness by studying individuals, but that only gets you so far. There's more to be learned by studying the group."
Christakis and his colleague James Fowler, a political scientist at the University of California, San Diego, drew their network of emotional states using data from the Framingham Heart Study.
This project has monitored the health of the people of Framingham, Massachusetts, since 1948. Christakis presented the latest findings on 25 June at the International Workshop and Conference on Network Science in Norwich, UK.
As well as gathering information on their physical health, the study collected data on people's emotional states, to see whether depression and heart disease are correlated.
Understandably enough, emotions are contagious over short distances and times. Waitresses who smile at their customers get bigger tips, and students with depressed roommates are more likely to get depressed themselves.
Christakis and Fowler also looked at the photos on the Facebook pages of a network of 1,700 students at an unnamed university in the northern United States.
The study found that smiley students clustered together. They were also closer to the centre of the network, and had more friends than those who didn't smile.
The research was presented on 25 June at the International Workshop and Conference on Network Science in Norwich, UK.