Does others' happiness make us happier? (Try not to smile.)
People who are surrounded by many happy people and those who are central in the network are more likely to become happy in the future.
James H. Fowler & Nicholas A. Christakis, Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study, Dec. 4, 2008, bmj.com.
