If you're not smiling in your Facebook photo, your life is probably going to suck in four years time.
Reseachers J. Patrick Seder and Shigehiro Oishi at the University of Virginia in Charlottesville discovered that smile intensity from a single Facebook profile photo in the first semester of college predicted self-reported life satisfaction three and a half years later, at the time of college graduation.
This type of study isn't actually unique to Facebook, however. A 2011 study by Harker and Keltner showed that female students smiling...