What are people thinking when they risk their lives for someone else? Are they making complicated calculations of risk or diving in without a second thought? Is heroism an act of sympathy or empathy?   A few years ago, we spoke with Walter F. Rutkowski about how the Carnegie Hero Fund selects its heroes, an honor the fund bestows upon ordinary people who have done extraordinary acts. When some of these heroes were asked what they were thinking when they leapt into action, they replied: they didn’t think about it, they just went in. Neuroscientist Robert Sapolsky says there is a certain kind of empathy that leads to action. But feeling the pain of another person deeply is not necessarily what makes a hero.   Our original episode was reported and produced by Lynn Levy and Tim Howard. This update was produced by Amanda Aronczyk. Support Radiolab today at Radiolab.org/donate.