From Who's Counting: Pictures, Statistics and Genocide
Slovic offers an evolutionary explanation for this decline in sympathy. Humans evolved in an environment where looking out for themselves and their families was their paramount concern.
There was no adaptive or survival value in protecting hundreds of thousands of people on the other side of the planet, he says.
Today, we have modern communications that can tell us about crises occurring on the other side of the world, but we are still reacting the same way as we would have long ago.