Vote Now on the Prisoner’s Dilemma Contest

We recently posted a contest, asking readers to choose the one question they’d ask if picking a partner to play the Prisoner’s Dilemma.

I did not expect this contest to generate more than 350 replies. Picking the single best out of 350 seemed impossible, so I thought we should winnow it down to the Top 5 and ask you to vote on the best.

But I happened to be out at the University of Chicago last week, and ran into someone who I realized would do a much better winnowing job than me. In fact, he’s probably more qualified to do so than just about anyone else in the world.

It’s our friend John List, a top-drawer experimental economist, whom you’ve read about on the blog before. I think you’ll agree that John’s explanations for why he chose what he chose are fascinating and illuminating. Thanks to all of you for participating and especially to John for his contribution. And don’t forget to vote.

What’s the Best Question to Select Your Prisoner’s Dilemma Partner
A Guest Post by John List

When Stephen recruited me for this chore, the marching orders he gave were simple: select the 5 best responses to his Prisoner’s Dilemma (PD) query.

Sounds simple, but actually making the choices was far from easy. The group here is a sophisticated lot that covered a great deal of ground and provided an array of novel responses. Nevertheless, at the cost of leaving out several worthy posts, I have narrowed the list to my Top 5. I attempted to include queries within the realm of “what is the best question to parse individual types,” to “what is the best way to coerce people,” to just outright fun queries.

A first rule in my family is that “If mama ain’t happy, nobody is happy,” so I included my wife Jen List‘s question, No. 114, in the Top 5:

“How old are you?”

Beyond familial ties, I like this response because it shows evidence of being a good consumer of the economics literature. For instance, in my own research I have found that age is importantly correlated to play in this class of games.

When analyzing outcomes from a game show called Friend or Foe, where players are playing the two-person PD game live while staring into each other’s eyes, I found that mature contestants tend to cooperate much more than younger ones. This is the case regardless of their partner’s age.

In a second paper, “Young, Selfish, and Male: Field Evidence of Social Preferences,” I conduct a field experiment that uses an anonymous n-player PD game.

The results on age and cooperation were quite similar and have been replicated in more recent economic experiments as well. For instance, Gächter, et al. (2004) found that older people are much more likely to perceive others to be helpful and fair, and, as a result, they are more likely to act cooperatively themselves.

Post #288, jrrd, gets at something similar as does post #343, Sarah, so I will work to convince Da Freaks to hand out extra schwag if this entry wins!

The second finalist provides a query in a similar spirit, but involves a type of “treatment” variable more in the spirit of indoctrination — post #342, G. Owen Schaefer:

“What is the number of ethics courses you’ve taken, minus the number of economics courses you’ve taken?”

Owen provides supporting documentation here.

One will readily learn from this literature that much of the research that examines differences in cooperativeness between economists and non-economists suffers from selection issues. That is, people who chose to become economists may do so because they were born or raised with a slant towards self-interestedness (another interesting question in and of itself!).

Some studies, however, have produced tentative evidence that economics training itself has effects, by comparing behavior among freshman and senior economics students (here, for example).

I should note that many others on the blog were also tuned into this type of query (e.g., #11, Craig, #129, Allison, #159, Cyrus).

The third finalist — post #268, Joe — goes about the differentiation in a unique manner by asking about the famous example used in the original Beautiful Mind movie about Nash‘s life:

“Given that you are in a bar, would you prefer to pursue the most attractive person in the bar, or would your efforts focus on someone less attractive?”

This seemingly superficial question gets at the following dilemma: if a group of young men are sitting in a bar and a group of women walk in, where one of them is particularly attractive — is it an optimal strategy for all of the young men to pursue the most beautiful woman? As Nash’s character reasons in the movie:

“If we all go after the blond we block each other. Not a single one of us is going to get her. So then we go for her friends. They will all give us the cold shoulder because nobody likes to be second choice. What if no one goes for the blond and we don’t insult the other girls? That’s the only way we win.”

To be fair, this is not exactly what the PD game is about but I was persuaded by the post’s originality. In fact, the one-shot PD game discussed in this post has what is called a “dominant strategy” to testify.

That is, regardless of what the other person does, it is always in your best interest to defect, or in this example, testify.

To see this most clearly, make a 2×2 matrix with your choices as the row entries (testify or remain silent) and the other person’s as the column entries. Insert the payoffs in terms of years in jail and you can see in a one-shot PD game that it is always in your best interest to testify. This is of course the crux of dilemma.

In fact, this famous example from the movie did not even provide a non-cooperative equilibrium to the game that Nash played that night (I fully suspect that night at the pub was made up altogether, but that is for a different blog post).

In the movie, all of the guys chose the marginal women as Nash directed, leaving the most physically attractive woman to seemingly go home alone. That certainly is not an equilibrium — if Nash played his own non-cooperative equilibrium concept, he would have changed his mind in this case and gone home with the most attractive woman!

In this manner, the movie was off in that it missed the essence of a non-cooperative equilibrium. Disappointing in and of itself, but enough of that, let’s move on.

The fourth entry is of the coercive spirit and is provided by post #257, Charles:

“What is the name and address of your most cherished family member?”

There were several entries of this form — posters noting mafia connections (#21, #48), contract killers (#316), rapists (#124), passing soap (#233), sexual molestation (#229), people’s mothers (#195); even Klondike Bars (#240) were mentioned.

But this particular entry induced the most cooperative spirit from me. Maybe it’s the family thing coming back to haunt me.

Finally, the fifth entry was given first in post #147, Colin:

“Do you read Freakonomics?”

This, of course, can serve as a useful question to parse individual types, but also might be important in its own right. Who wants to go to prison with someone who has not read Freakonomics? Recall that if you both testify you will be sent to jail for 5 years, so why not spend it with a fellow Freakonomics reader? I can think of much less desirable company.

So there you have it. Apologies to those I left off the list, and congrats to those who made it. As they say here in Chicago, vote early and vote often — and don’t be afraid to bring a few of your dead friends and relatives to the polls.

So here are your five choices:

1. “How old are you?”

2. “What is the number of ethics courses you’ve taken, minus the number of economics courses you’ve taken?”

3. “Given that you are in a bar, would you prefer to pursue the most attractive person in the bar, or would your efforts focus on someone less attractive?”

4. “What is the name and address of your most cherished family member?”

5. “Have you read Freakonomics?”

Whichever choice gets the most votes in the comments section within 48 hours of this posting (barring obvious fraud) will receive her/his choice of Freakonomics schwag.