The Harvard Study of Adult Development, which began in 1938, is one of the longest-running studies of adult life ever conducted. Eight decades later, and studying the third generations of its original participants, the researchers have arrived at one simple conclusion to what makes people happy.

"Good relationships keep us happier, healthier, and help us live longer," writes Dr. Robert Waldinger, director of the study, in the new book The Good Life: Lessons from the World’s Longest Scientific Study of Happiness. "This is true across the lifespan, and across cultures and contexts, which means it is almost certainly true for you, and for nearly every human being who has ever lived."

In this week's video, Dr. Waldinger chats with CBS reporter Susan Spencer about his research, the new book, and how to strengthen your relationships. If you've got more time, check out Dr. Waldinger's TED Talk on his happiness research.

New to NCFR? Our members are dedicated to understanding and strengthening families and relationships. Learn more.