This paper delineates the diminishing sensitivity in valuing lifesaving interventions when there is an increasing number of lives at risk. The authors call this tendency “psychophysical numbing”, represented in later research by the “collapse of compassion” model.For illustrative purposes, the top image to the right represents a normative model of how we should value human lives, the bottom image represents the collapse model that this research investigates.This paper has 3 studies illustrating psychophysical numbing in different contexts. In one study subjects had to decide which medical institution to award $10 million to – A, B or C. Subjects had to indicate how many lives would have to be saved by the treatment to merit receiving the award.A – Would save 15,000 lives.B – Would save 160,000.C – Would save 290,000.65% of participants gave estimates that increased as the size of the population at risk increased (indicating something like the collapse model is at work). Only 28% gave required that the same number be saved, regardless of population size (indicating a normative model).