"The death of one man is a tragedy, the death of millions is a statistic."

That's what Soviet dictator Joseph Stalin allegedly once said to U.S. ambassador Averill Harriman. And Stalin was an expert on the topic since his regime killed as many 43 million people. It turns out that the mustachioed murderer may have been expressing an acute insight into human psychology. Earlier this week, the Washington Post's always interesting Department of Human Behavior columnist Shankar Vedantam reported on the research of University of Oregon professor Paul Slovic who looked at how people respond to humanitarian tragedies. As Vedantam explains:

In a rational world, we should care twice as much about a tragedy affecting 100 people as about one affecting 50. We ought to care 80,000 times as much when a tragedy involves 4 million lives rather than 50. But Slovic has proved in experiments that this is not how the mind works.

When a tragedy claims many lives, we often care less than if a tragedy claims only a few lives. When there are many victims, we find it easier to look the other way.

Virtually by definition, the central feature of humanitarian disasters and genocide is that there are a large number of victims.

"The first life lost is very precious, but we don't react very much to the difference between 88 deaths and 87 deaths," Slovic said in an interview. "You don't feel worse about 88 than you do about 87."

Slovic did one experiment shortly after the Rwandan genocide. He asked volunteers whether they were willing to spend precious resources getting water to a refugee camp in Zaire, now called Congo. There were many pressing demands for the money, but Slovic told the volunteers that the water could save 4,500 lives. Without the volunteers' awareness, however, the researcher told some people the refugee camp had 11,000 people while telling others that the camp had 100,000 people. The number of lives that could be saved was the same in both cases—4,500—but Slovic found that people were reluctant to divert resources to save lives in a large camp rather than the same number of lives in a small camp.

In another experiment, Slovic asked people to imagine they were disbursing money on behalf of a large foundation: They could give $10 million to fight a disease that claimed 20,000 lives a year—and save 10,000 of those lives. But they could also devote the $10 million to fight a disease that claimed 290,000 lives a year—and this investment would save 20,000 lives.

Slovic found that people preferred to spend the money saving the 10,000 lives in the first scenario rather than the 20,000 lives in the second scenario: "People were responding not to the number of lives saved but the percentage of lives saved," he said. In the one case, their investment could save half the victims; in the case of the more deadly disease, it could save 7 percent of the victims.

There are parallels between such behavior and how we perceive physical sensations, and evolution's hand in shaping the way we perceive physical sensations may be behind the errors we make in judging suffering among our fellow humans. We are sharply aware of the difference between total darkness and the light thrown off by a five-watt bulb, but we are hard pressed to tell the lighting difference between a 90-watt bulb and a 100-watt one.

Slovic said people probably are inappropriately—and unconsciously—using a similar metric in humanitarian crises: Failing to save only half the victims in a tragedy seems less dreadful than failing to save 93 percent of the victims of another tragedy. The mathematical side of our brain could tell us the absolute number of victims saved is more important than the percentage of survivors, but our analytical side isn't usually in charge.

Slovic has also shown that the amount of compassion humans feel can diminish as the number of victims increases: In an experiment in Israel, Slovic asked volunteers whether they would help raise $300,000 to save eight children who were dying of cancer. Those in another group were told only about one child with cancer and asked how much they were willing to donate to save the life of that child. Slovic found that people were willing to give more money to save one life than to save eight.

"When we trust our feelings in these cases, we are led down the path of turning our backs on the suffering of many people," Slovic said. "Even though we don't think of ourselves as uncaring, if we trust our moral intuition, it is not designed by evolution to respond accurately to these types of situations of mass tragedy."

Fascinating. Whole Post article here.