According to science, humans are a combination of nature and nurture when it comes to generosity. The brain rewards you with a shot of feel-good dopamine when you are generous. That delicious hormone literally sizzles through your bloodstream when you take your imaginary generosity gland for a whirl. It is a biological boomerang: give to someone who needs it and the joy will bounce right back at you as a warm fuzzy feeling of reward and delight.