The neural basis for empathy may be a system of mirror neurons. These nerve cells are activated both during an action and observing someone else performing the action.
"It's hotly debated, but there's some evidence suggesting that the mirror system functions atypically in autism," Pfeifer said.
Researchers are just beginning to explore methods of repairing the system when it appears to be dysfunctioning.
"There's also pretty good evidence that there are wide individual differences in how much systems are engaged in response to seeing someone else in distress," Pfeifer said.
Roger Griffin, a professor at Oxford Brookes University in England and expert on terrorism, understands the challenges in understanding empathy from both a personal and professional standpoint.
As the author of "Terrorist's Creed: Fanatical Violence and the Human Need for Meaning," he knows that fanatical violence and sociopathic killing usually involve a dysfunction in empathy. And, from the way boys of his son's age (14) behave with their peers and parents, he sees that even those who seem well-adjusted, socially well-integrated, and academically successful occasionally have lapses in which empathy is replaced by violent verbal outbursts and threatening physicality -- a pattern he believes is fueled by video games that celebrate violence and criminality.