Repugnant Intuitions

Derek Parfit’s Repugnant Conclusion has long been a focus area in the field of population ethics, as it seems to imply counterintuitive (or repugnant) tradeoffs when taking a utilitarian view. As Parfit states it, the Repugnant Conclusion suggests that:

“For any possible population of at least ten billion people, all with a very high quality of life, there must be some much larger imaginable population whose existence, if other things are equal, would be better even though its members have lives that are barely worth living” (Parfit 1984).

This conclusion occurs as a result of taking a utilitarian view, where total happiness / utility should be maximized; the total utility of a much larger population with low individual utility can always be larger than the sum of a smaller population with very high individual utility. 

For most people, this conclusion doesn’t feel right, and a variety of attempts have been made to adjust the ethical framework accordingly. The page linked above goes into greater detail on these strategies, which involve such adjustments as aggregating utility in different ways (e.g. considering the average rather than the sum), separating utility into distinct classes with different rankings, narrowing the population to be considered (to only those appearing in both populations being compared), declaring that no life is worth living (a bold conjecture!), and rejecting transitivity. Clearly, the Repugnant Conclusion does not sit well with many people – or at least, does not sit well with their immediate intuitions. Before evaluating the conclusion any further, it will be helpful to try and better understand these intuitions by taking a leap into the world of Daniel Kahneman and behavioral science. The below passages are from Kahneman’s magnum opus, Thinking, Fast and Slow:

The psychologist Ed Diener and his students wondered whether duration neglect and the peak-end rule would govern evaluations of entire lives. They used a short description of the life of a fictitious character called Jen, a never-married woman with no children, who died instantly and painlessly in an automobile accident. In one version of Jen’s story, she was extremely happy throughout her life (which lasted either 30 or 60 years), enjoying her work, taking vacations, spending time with her friends and on her hobbies. Another version added 5 extra years to Jen’s life, who now died either when she was 35 or 65. The extra years were described as pleasant but less so than before. After reading a schematic biography of Jen, each participant answered two questions: “Taking her life as a whole, how desirable do you think Jen’s life was?” and “How much total happiness or unhappiness would you say that Jen experienced in her life?”

Take a minute and think about how you might answer the questions for each of the scenarios before moving on.

The results provided clear evidence of both duration neglect and a peak-end effect. In a between-subjects experiment (different participants saw different forms), doubling the duration of Jen’s life had no effect whatsoever on the desirability of her life, or on judgements of the total happiness that Jen experienced. Clearly, her life was represented by a prototypical slice of time, not as a sequence of time slices.

As expected from this idea, Diener and his students also found a less-is-more effect, a strong indication that an average (prototype) has been substituted for a sum. Adding 5 “slightly happy” years to a very happy life caused a substantial drop in evaluations of the total happiness of that life.

At [Kahneman’s] urging, they also collected data on the effect of the extra 5 years in a within-subject experiment; each participant made both judgements in immediate succession. In spite of [Kahneman’s] long experience with judgement errors, [he] did not believe that reasonable people could say that adding 5 slightly happy years to a life would make it substantially worse. [He] was wrong. The intuition that the disappointing extra 5 years made the whole life worse was overwhelming.

The pattern of judgements seemed so absurd that Diener and his students initially thought that it represented the folly of the young people who participated in the experiments. However, the pattern did not change when the parents and older friends of students answered the same questions. In intuitive evaluation of entire lives as well as brief episodes, peaks and ends matter but duration does not. (pp. 387 – 388)

In one of many experiments that were prompted by the litigation about the notorious Exxon Valdez oil spill, participants were asked about their willingness to pay for nets to cover oil ponds in which migratory birds often drown. Different groups of participants stated their willingness to pay to save 2,000, 20,000, or 200,000 birds. If saving birds is an economic good it should be a sum-like variable: saving 200,000 birds should be worth much more than saving 2,000 birds. In fact, the average contributions of the three groups were $80, $78, and $88 respectively. The number of birds made very little difference. What the participants reacted to, in all three groups, was a prototype – the awful image of a helpless bird drowning, its feathers soaked in thick oil. (pp. 93)

Our intuitions certainly seem to have some flaws, with direct implications for the Repugnant Conclusion. Rather than evaluating the two populations (few with high utility vs. many with low utility) in a rigorous manner, it seems we may simplify the question by instead comparing the prototypes or averages of each population (i.e. a very high utility person vs. a very low utility person). It’s difficult for us to grasp what it means for 100 high utility people to exist, and even more difficult to grasp the idea of 100 million low utility people (making it near impossible to actually compare the two populations intuitively). Parfit identified an interesting phenomenon worthy of consideration, but may have focused on the wrong part of it; rather than asking how to solve the Repugnant Conclusion, he may have gotten further by asking instead why we find it repugnant.