Insensitivity To The Value Of Human Life: A Study Of Psychophysical Numbing

Fetherstonhaugh, David; Slovic, Paul; Johnson, Stephen; Friedrich, James, (1997). Insensitivity To The Value Of Human Life: A Study Of Psychophysical Numbing. Journal Of Risk And Uncertainty, 14, 3, 283–300.



Type of evidence: Hypothetical/intentional experiment

Related tools: Present small "base group"

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Paper summary



Studies 1 and 2 found that an intervention saving a fixed number of lives was judged significantly more beneficial when fewer lives were at risk overall. Study 3 found that respondents wanted the

minimum number of lives a medical treatment would have to save to merit a fixed amount of funding to be much greater for a disease with a larger number of potential victims than for a disease with a smaller number.

Study 1: Respondents evaluated the programs in pairs, one pair per page
We predicted that preference ratings would be greater for the small-camp program than the large-camp program. Because these programs were never paired together, however, we compared respondents’ ratings for the two Rwandan programs in pairings that shared a common non-Rwandan program
Even though most respondents realized that the same number of refugees could be saved in either camp, they preferred the small-camp program (M 5 .45) over the large-camp program (M 5 2.20) when paired with either the transportation or employment programs.
Study 2 omitted dummy scenarios and had respondents evaluate Rwandan scenarios individually.
… manipulated three within-subjects variables: size of refugee camp (11,000 or 250,000), amount of pure-water aid a camp was receiving before a water-purification plane was sent (low or high), and reliability of the plane (60% or 100%). … eight different scenarios participants read… 2 x 2 x 2 repeated-measures factorial design. All respondents evaluated the same eight scenarios
two dependent variables: (1) the rated benefit of sending a plane, and (2) a yes/no decision on whether or not to send a plane.
A 2 x 2 x 2 within-subjects ANOVA on respondents’ benefit ratings provided strong support for the psychophysical numbing hypothesis (see Figure 2). A significant main effect for camp size, F (1, 132) 160.5, p .001, indicated that respondents believed sending the planes to small camps was more beneficial (M 6.46) than sending them to large camps (M 4.54). A main effect for the prior-aid variable, F (1, 132) 15.35, p .001, indicated that respondents believed sending the planes to camps that were already satisfying a substantial portion of their clean-water need was more beneficial (M 5.73) than sending them to camps that were only satisfying a small portion of their water need (M 5.27).


Participants were less likely to allocate money to a hypothetical refugee camp when they could only save 1500 lives out of 250,000 refugees rather than 1500 lives out of 11,000. … Fetherstonhaugh et al. use the term “drop in the bucket” to describe the thought process that might bring about these decisions: saving a tiny percentage of a population could feel useless even if 1500 individuals still get the chance to live.


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