Scope Insensitivity

Once upon a time, three groups of sub­jects were asked how much they would pay to save 2,000 /​ 20,000 /​ 200,000 mi­grat­ing birds from drown­ing in un­cov­ered oil ponds. The groups re­spec­tively an­swered $80, $78, and $88.1 This is scope in­sen­si­tivity or scope ne­glect : the num­ber of birds saved—the scope of the al­tru­is­tic ac­tion—had lit­tle effect on will­ing­ness to pay.

Similar ex­per­i­ments showed that Toronto res­i­dents would pay lit­tle more to clean up all pol­luted lakes in On­tario than pol­luted lakes in a par­tic­u­lar re­gion of On­tario, or that res­i­dents of four west­ern US states would pay only 28% more to pro­tect all 57 wilder­ness ar­eas in those states than to pro­tect a sin­gle area.2 Peo­ple vi­su­al­ize “a sin­gle ex­hausted bird, its feathers soaked in black oil, un­able to es­cape.”3 This image, or pro­to­type, calls forth some level of emo­tional arousal that is pri­mar­ily re­spon­si­ble for will­ing­ness-to-pay—and the image is the same in all cases. As for scope, it gets tossed out the win­dow—no hu­man can vi­su­al­ize 2,000 birds at once, let alone 200,000. The usual find­ing is that ex­po­nen­tial in­creases in scope cre­ate lin­ear in­creases in will­ing­ness-to-pay—per­haps cor­re­spond­ing to the lin­ear time for our eyes to glaze over the ze­roes; this small amount of af­fect is added, not mul­ti­plied, with the pro­to­type af­fect. This hy­poth­e­sis is known as “val­u­a­tion by pro­to­type.”

An al­ter­na­tive hy­poth­e­sis is “pur­chase of moral satis­fac­tion.” Peo­ple spend enough money to cre­ate a warm glow in them­selves, a sense of hav­ing done their duty. The level of spend­ing needed to pur­chase a warm glow de­pends on per­son­al­ity and fi­nan­cial situ­a­tion, but it cer­tainly has noth­ing to do with the num­ber of birds.

We are in­sen­si­tive to scope even when hu­man lives are at stake: In­creas­ing the alleged risk of chlo­ri­nated drink­ing wa­ter from 0.004 to 2.43 an­nual deaths per 1,000—a fac­tor of 600—in­creased will­ing­ness-to-pay from $3.78 to $15.23.4 Baron and Greene found no effect from vary­ing lives saved by a fac­tor of 10.5

A pa­per en­ti­tled “Insen­si­tivity to the value of hu­man life: A study of psy­chophys­i­cal numb­ing” col­lected ev­i­dence that our per­cep­tion of hu­man deaths fol­lows We­ber’s Law—obeys a log­a­r­ith­mic scale where the “just no­tice­able differ­ence” is a con­stant frac­tion of the whole. A pro­posed health pro­gram to save the lives of Rwan­dan re­fugees gar­nered far higher sup­port when it promised to save 4,500 lives in a camp of 11,000 re­fugees, rather than 4,500 in a camp of 250,000. A po­ten­tial dis­ease cure had to promise to save far more lives in or­der to be judged wor­thy of fund­ing, if the dis­ease was origi­nally stated to have kil­led 290,000 rather than 160,000 or 15,000 peo­ple per year.6

The moral: If you want to be an effec­tive al­tru­ist, you have to think it through with the part of your brain that pro­cesses those un­ex­cit­ing inky ze­roes on pa­per, not just the part that gets real worked up about that poor strug­gling oil-soaked bird.

1 William H. Desvous­ges et al., Mea­sur­ing Nonuse Da­m­ages Us­ing Contin­gent Valu­a­tion: An Ex­per­i­men­tal Eval­u­a­tion of Ac­cu­racy, tech­ni­cal re­port (Re­search Tri­an­gle Park, NC: RTI In­ter­na­tional, 2010).

2 Daniel Kah­ne­man, “Com­ments by Pro­fes­sor Daniel Kah­ne­man,” in Valu­ing En­vi­ron­men­tal Goods: An Assess­ment of the Contin­gent Valu­a­tion Method, ed. Ron­ald G. Cum­mings, David S. Brook­shire, and William D. Schulze, vol. 1.B, Ex­per­i­men­tal Meth­ods for Assess­ing En­vi­ron­men­tal Benefits (To­towa, NJ: Row­man & Allan­held, 1986), 226–235; Daniel L. McFad­den and Gre­gory K. Leonard, “Is­sues in the Contin­gent Valu­a­tion of En­vi­ron­men­tal Goods: Method­olo­gies for Data Col­lec­tion and Anal­y­sis,” in Contin­gent Valu­a­tion: A Crit­i­cal Assess­ment, ed. Jerry A. Haus­man, Con­tri­bu­tions to Eco­nomic Anal­y­sis220 (New York: North-Hol­land, 1993), 165–215.

3Daniel Kah­ne­man, Ilana Ri­tov, and David Schkade, “Eco­nomic Prefer­ences or At­ti­tude Ex­pres­sions?: An Anal­y­sis of Dol­lar Re­sponses to Public Is­sues,” Jour­nal of Risk and Uncer­tainty 19, nos. 1–3 (1999): 203–235.

4Richard T. Car­son and Robert Cameron Mitchell, “Se­quenc­ing and Nest­ing in Contin­gent Valu­a­tion Sur­veys,” Jour­nal of En­vi­ron­men­tal Eco­nomics and Man­age­ment 28, no. 2 (1995): 155–173.

5Jonathan Baron and Joshua D. Greene, “Deter­mi­nants of Insen­si­tivity to Quan­tity in Valu­a­tion of Public Goods: Con­tri­bu­tion, Warm Glow, Bud­get Con­straints, Availa­bil­ity, and Promi­nence,” Jour­nal of Ex­per­i­men­tal Psy­chol­ogy: Ap­plied 2, no. 2 (1996): 107–125.

6David Fether­ston­haugh et al., “Insen­si­tivity to the Value of Hu­man Life: A Study of Psy­chophys­i­cal Numb­ing,” Jour­nal of Risk and Uncer­tainty 14, no. 3 (1997): 283–300.