A mother gazes into her baby's eyes, and he responds with a smile and cooing sounds of happiness. A man asks a woman to marry him, and she throws her arms around him, kisses him, and says "yes," her eyes filling with tears. An elderly woman in a nursing home is visited by two close friends, and her vital statistics show immediate and unexpected improvement. Each of these examples illustrates a universal truth: When we know we are loved, it shows. Or to put it another way: Love begets love.