How long would you hesitate before pushing someone in front of a runaway train to keep it from killing five other people? The answer may be no time at all, if you have damage to the ventromedial prefrontal cortex (VMPC)—a region in the forebrain associated with emotional response. Researchers confronted volunteers with such scenarios and found that those with VMPC injury were three times more likely than healthy people to advocate throwing the person to certain death for the good of the many. In a similar scenario, VMPC patients were five times more likely to advocate smothering one's baby to save others. Senior author Antonio Damasio of the University of Southern California says that the patients are not amoral but seem to lack the natural conflict between emotion and reason. The study, in the March 22 Nature, also shows that such decisions result not from a single moral faculty but from two different processes that can compete with each other.