J.F. AAS - August 1996
PD, Multiple Brain, ULYSSES & SOCIAL CAPITAL:
Saving Water In A Drought
In a severe drought, many would agree that it would be desirable to eliminate non-essential uses. Still, some may not restrain themselves if they are not sure others will restrain their uses, or if they forget the long term consequences. How can this be modeled as a Prisoner's Dilemma problem and is the metaphor of Ulyssses helpful (as used by Jon Elster)?
The problem with metaphors is that they are only as good as the common understanding of the story -- or it takes longer to explain the story than the original point.
Anyway, the Ulysses myth is useful to add to your metaphor collection for future use with people who know it. Ulysses knew that the beautiful sirens lured sailors to certain death on the rocks where they lived. He knew in one part of his brain that the sirens were desirable. In another part (call it the planner brain) he knew they were on the rocks. He was afraid that the immediate pleasure brain might control action if the sirens were sighted. So the planner brain tried to protect against this eventuality by asking his crew to tie his body to the mast so he could not guide the ship to the sirens. The planner brain wanted to control the immediate pleasure brain. This is a conflict within the individual (multiple self) rather than a conflict between Ulysses and the crew -- individual vs. society. This internal conflict is not anticipated in standard utility theory where there is just one unified preference map.
What is the application to the drought and the language of prisoner's dilemma? The problem of PD is not a conflict over the desirability of jail. It is not a conflict between the individual and society (other prisoners). Both would prefer to go free. The problem is that the individuals as individuals can't get what they want acting at the margin of individual choice. The problem is not that person A gets what she wants and person B loses. The problem is that both A & B lose. The individuals cannot get what they want unless they act collectively. This is not the same as saying that the individual and the others conflict. It is true that at the margin each trying to maximize their utility screws the other guy, but they also get screwed. The point of social capital here is not that A must love B enough to lose so B can gain. But rather that social capital will help both extract themselves from the isolated choice situation so that both can win. As Robert Frank shows, the emotional content of social capital helps solve the commitment problem. The character of the commitment problem is not captured by the language of individuals having conflicting preferences (individual vs. society). Emotion (social capital) lets the planner brain win over the immediate pleasure brain.
Real world problems have many dimensions. In a drought there are those deeply concerned about having enough to drink if the drought is prolonged and others who are willing to take their chances -- drink today and let tomorrow take care of itself. This can be described in the language of one individual(s) vs. others. But even among those who want conservation, they are subject to PD. Since the future supply is available to savers and wasters equally, there is a problem of commitment among those who want the conservation results (share the same preferences) as well as a conflict between their planner brains and immediate pleasure brains. The planner brain will want to join with other planner brains to tie the hands (shall we say mouth?) Of the other self that says "eat, drink, wash your car, and be merry." The planner brain says, don't make the best choice within a poor marginal choice set, but rather join with others to create a set that otherwise will not exist.
If you have any questions or comments, please email schmid@pilot.msu.edu 
