STEVE EMBER: Professor Mikhail says good Samaritan laws protect the intuition, the natural sense, that people have to help others in need.

JOHN MIKHAIL: "Couple interesting points about this. One is that the intuition is shared even by young children. And the second is that the intuition is shared across the world."

And he should know. John Mikhail is the author of a new book called "Elements of Moral Cognition." It describes experiments in which he and his colleagues asked people about situations where someone needed help. Professor Mikhail says everyone, no matter what country they were from, expressed a willingness to intervene.

Yet last month there was the story of a two-year-old girl in southern China who was hit by a truck at a street market. Security cameras showed that for seven minutes, no one stopped to help. Then another truck hit her. Finally, a stranger pulled the child to the side of the road. Wang Yue died in a hospital more than a week later.

Her tragic story led to debate and discussion in China and elsewhere about what it means to be a good Samaritan.

FAITH LAPIDUS: So why don't people always help? Social scientists have spent years studying what they call the bystander effect. This involves the social influences that make groups of people less likely to help as they witness a troubling situation.

But Robert Cloninger, the psychiatrist, says that among individuals, there are many reasons why people may decide not to act. They might feel afraid they are going to get hurt themselves. They might have had bad experiences in the past. Or they might not get pleasure out of being kind to others.