This can happen during our most basic exchanges, say on your commute to work. “If someone smiles at you, you smile back at them,” says sociologist Nicholas Christakis of Yale University. “That’s a very fleeting contagion of emotion from one person to another.”
But it doesn’t stop there. Emotions can spread through social networks almost like the flu or a cold. And the extent to which emotions can cascade is eye-opening.
For instance, Christakis’ research has shown that if you start to become happier with your life, a friend living close by has a 25 percent higher chance of becoming happy too. And your partner is more likely to feel better as well. The happiness can even spread to people to whom you’re indirectly connected…