Scope insensitivity is the finding that people's willingness to pay to address a problem often barely changes even as the actual scale of the problem changes dramatically — because the emotional reaction driving the willingness to pay is triggered by a single vivid mental image, not by an accurate sense of quantity. Saving 2,000 birds and saving 200,000 birds can trigger essentially the same felt reaction (one oil-soaked bird, multiplied in the mind by an unfelt, abstract factor), even though the actual difference in scale is a hundredfold.
This has serious practical implications for how charitable appeals, public policy communication, and cost-benefit analysis get evaluated by the public: an appeal built around a single vivid case will often out-persuade an appeal built around accurate, large-scale statistics, even when the statistics represent dramatically more actual impact.
In litigation research following the 1989 Exxon Valdez oil spill, researchers asked different groups of people how much they'd be willing to pay to prevent 2,000, 20,000, or 200,000 oiled migratory birds from drowning in future spills. The average amounts people offered across the three groups — $80, $78, and $88 — were nearly identical, despite the actual scale of the problem spanning a hundredfold range across the three versions of the question.