Shankar Vedantam:

Nations tend to focus far more time, money and attention on tragedies caused by human actions than on the tragedies that cause the greatest amount of human suffering or take the greatest toll in terms of lives. … In recent years, a large number of psychological experiments have found that when confronted by tragedy, people fall back on certain mental rules of thumb, or heuristics, to guide their moral reasoning. When a tragedy occurs, we instantly ask who or what caused it. When we find a human hand behind the tragedy — such as terrorists, in the case of the Mumbai attacks — something clicks in our minds that makes the tragedy seem worse than if it had been caused by an act of nature, disease or even human apathy. …

Tragedies, in other words, cause individuals and nations to behave a little like the detectives who populate television murder mystery shows: We spend nearly all our time on the victims of killers and rapists and very little on the victims of car accidents and smoking-related lung cancer. "We think harms of actions are much worse than harms of omission," said Jonathan Baron, a psychologist at the University of Pennsylvania. "We want to punish those who act and cause harm much more than those who do nothing and cause harm. We have more sympathy for the victims of acts rather than the victims of omission. If you ask how much should victims be compensated, [we feel] victims harmed through actions deserve higher compensation."

This bias should also afflict our future thinking, making us worry more about evil alien intent than unintentional catastrophe.