We see a man laughing and we smile in response. Our heart goes out to the sad-looking woman on the train. Humans are empathetic creatures - we feel what others feel, even the emotions of strangers. And it may be due to brain cells that researchers have only recently discovered: mirror neurons. Find out how these mimicking cells help us survive cocktail parties, keep society humming, and even give rise to the concept of self.
Also, are humans born with a moral code? And, if human behavior is hard-wired - whatever becomes of free will?