DAVID NIVEN, PhD, is known internationally for translating powerful research findings into practical advice anyone can apply to their daily lives. David's The 100 Simple Secrets of Happy People - and seven other titles in the series - have sold more than 1 million copies in the U.S., and has been translated in 30 languages around the globe. His work has been featured in USA TODAY, US Weekly, The Washington Post, Reader's Digest, Redbook, Cosmopolitan, Glamour, and Health.