Happy people make other people happy. Being around happy people increases an individual's chances of being happy, according to a study conducted by Nicholas Christakis and others at Harvard University . The study surveyed 4,700 people for 20 years to determine how emotion transfers through groups of people (Rob Stein, "Happiness Can Spread Among People Like a Contagion, Study Indicates," The Washington Post, Dec. 5, 2008).

The book of Proverbs had a nearly 3,000-year head start on this new survey. "A merry heart does good, like medicine" (Proverbs 17:22) is a nugget of wisdom that benefits humankind in any era of history.