University of Kansas, Fall 2004
Philosophy 160: Introduction to Ethics
Ben Eggleston—eggleston@ku.edu

The Prisoner’s Dilemma

It is essential to understanding social-contract theory to be able to understand what is and what is not a prisoner’s dilemma sort of situation. Speaking abstractly, a situation is a prisoner’s dilemma sort of situation if each individual has two actions—let’s call them C and D—such that the following two statements are true:

  1. Regardless of what other people are doing—regardless, that is, of the number of other people doing C versus D—any given individual can expect to benefit more from doing D than from doing C.
  2. Each individual can expect to benefit more from (a) the outcome that results if everyone does C than (b) the outcome that results if everyone does D.

Given this characterization of prisoner’s dilemma types of situations, consider each of the following situations and figure out whether the two statements are true or false. Put T or F in each of the columns labeled 1 and 2, as appropriate, and then put a ‘Y’ in the column labeled ‘PD?’ if and only if you identified statements 1 and 2 as true. Otherwise, put an ‘N’ in that column.

situation 1 2 PD?
1 The people of Kansas City can either drive to work (D) or take the bus (C). Currently (let us suppose), nearly everyone drives to work, and the average commute by car takes 45 minutes, with the average commute by bus taking an hour. If nearly everyone took the bus to work, then the decrease in traffic and increased capacity of the bus system would make the average commute, by bus, fall to 20 minutes. But then the average commute by car would take only 15 minutes, because in this city, regardless of the number of people taking the bus, driving one’s own car takes only three-fourths as much time as taking the bus.      
2 The people of Los Angeles have a pollution problem. Suppose that one way to partially solve the problem is for each person to buy a pollution filter for his or her car that will decrease the pollution it emits (C). The filter costs $100, and has to be replaced every year. Every person would, if he or she had the option, spend $100 per year to buy the cleaner air that would result if everyone used one of these devices. But no one benefits enough from putting the device just on his or her own car to regard the $100 expense as worthwhile.      
3 In any city or town, there is a lot of driving going on. Everyone can drive carefully (C) or recklessly (D). People who drive recklessly risk injury and property damage to themselves and other people. So, it’s in any given person’s interest to drive carefully rather than recklessly. Also, other people prefer for that person to drive carefully, so that they (the other people) are put in less danger.      
4 One hundred students are in a class in which there is just one assignment—a cumulative final exam determining the entire course grade. The raw scores attained on the final exam will be adjusted to a pre-set curve, so that there will be two 100’s, two 99’s, two 98’s, and so on, down to two 51’s, regardless of what the initial raw scores were. Each student can study a little (C) or a lot (D) (and suppose there is no way to study an in-between amount). Although every student would prefer to study as little as possible (other things being equal), any student who studies a lot can expect to get a much higher raw score than if he or she studies a little. If every student studies a lot, then each student’s final grade will be the same as if every student studies a little (this is, studying a lot does every student the same amount of good).      
5 The situation is the same as in number 4, except that the raw scores are not adjusted to a pre-set curve. So, if every student studies a lot, then each student’s final grade will be higher than if every student studies a little, and the increase in final grade is large enough to offset the cost or inconvenience, for each student, of studying a lot versus studying a little.      
6 Suppose there is a city in which the cable-TV company is not very careful about making sure that non-subscribers cannot view its signal. (Maybe the boxes are easy to tamper with, or the lines are easy to splice, etc.) So, it is feasible to get cable for free (D). If everyone did this, then the company would have no revenue, and it would go out of business. If everyone subscribed (C), then it would cost $20 per month per person. Suppose, finally, that everyone regards cable as a pretty good value when the price is $20 per month.