More than two decades ago, psychologist Christopher Peterson discovered that optimists live longer than pessimists. His subsequent research linked optimism to improved cardiovascular health, fewer accidental injuries, and -- as he documented in a paper published this summer -- reduced likelihood of stroke. But why would optimism lead to better health outcomes? In a recent Bloggingheads.tv diavlog, Peterson offered his paradoxical answer.

How did Peterson first make the connection between optimism and health? It goes back to WWII-era Harvard students and the mysterious "death by other."