The human brain cannot release enough neurotransmitters to feel emotion a thousand times as strong as the grief of one funeral. A prospective risk going from 10,000,000 deaths to 100,000,000 deaths does not multiply by ten the strength of our determination to stop it. It adds one more zero on paper for our eyes to glaze over.

Cognitive Biases Potentially Affecting Judgment of Global Risks, a chapter of Global Catastrophic Risks, edited by Nick Bostrom and Milan M. Cirkovic (2008)