A pioneer in research on play, Dr. Stuart Brown says humor, games, roughhousing, flirtation and fantasy are more than just fun. Plenty of play in childhood makes for happy, smart adults -- and keeping it up can make us smarter at any age.

When you're feeling burned out as an activist, what's the best way to bounce back? TED Senior Fellow Yana Buhrer Tavanier explores the power of "playtivism" -- the incorporation of play and creativity into movements for social change. See how this versatile approach can spark new ideas, propel action and melt fear.

"Do what you love" is often terrible advice. Instead of taking the job that will make you happiest, look for the one where you'll learn the most. (Audio only)