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Polyamory and the Prisoner's Dilemma...

...or, how to quit worrying and love your partner's other partners.

Right now, I'm about midway through reading the book How We Know what Isn't So: The Fallibility of Human Reason in Everyday Life, by Thomas Gilovich. As the title suggests, it's essentially a catalog of the various cognitive traps, reasoning errors, and other fallibilities that lead to people to "knowing" things that aren't true. (sarahmichigan, if you haven't read this book yet, I suspect you'd quite like it.)

The book talks about a lot of reasoning problems that you might expect: confirmational bias, for example, and intuitive problems with randomness (the human brain is so highly optimized for seeking patterns that it'll find patterns even in random data, and on top of that, random data do not necessarily "look" the way we expect them to, and in particular aren't fractal in nature; it's perfectly reasonable to flip a coin a bunch of times and see heads come up five or six times in a row...but I digress).

It also discusses people's tendency to make evaluations based on missing or absent data; if, for example, you believe that people who have less than a certain GPA should not be admitted to college, because they would tend to do poorly, so you admit only people with a high GPA and you notice everyone doing well, you might be tempted to believe smugly that your decisions are good and your impulses correct, but you are missing the very data that would confirm or deny your hypothesis. because you refuse to let people with a low GPA in, you have no way to know if their performance would be poor or not.

And it discusses self-fulfilling prophesies, in the context of the Prisoner's Dilemma.




A quick recap for anyone who may be unfamiliar with the Prisoner's Dilemma: a Prisoner's Dilemma problem is any situation where two people can choose to cooperate with one another or to work against one another, such that if they both cooperate they both gain something, if they both defect they both lose something, but if one cooperates and one defects, the one who cooperates loses catastrophically and the one who defects gains tremendously.

It got its name from the way it was originally couched: Suppose you and a complete stranger, who you've never had any contact with before, get together to commit a crime. You are caught in the middle of committing the crime and whisked away by police to separate cells, with no opportunity to speak to one another. The police interrogate you separately, and tell you that each of you is being given the following choice: you can keep quiet, or you can testify against the other.

If you both keep quiet, there is only circumstantial evidence against you, and you'll both likely be convicted of lesser charges and go to prison for two years each.

If you both testify against each other, each of you can expect a ten-year prison sentence.

If one of you keeps quiet and the other testifies, the person who keeps quiet will be imprisoned for twenty years, and the person who testifies will get off scott-free. What do you do?

The best possible outcome is for both of you to shut up. However, if you have any doubt whatsoever about your partner's willingness to shut up, then you better testify, because if he testifies and you don't, you're in big trouble! Since he is using the same reasoning as you are, then if he doubts you, his best course of action is to testify. Since both of you can't predict the action of the other, what will probably happen is that both of you will testify (and spend the next decade behind bars) rather than both keeping your mouth shut (in which case oyu'd both be freed in one-fifth the time).

Things change a bit if you play this game iteratively. Suppose that you have money and you wish to buy something from someone else, but because of the nature of what you want to buy (maybe it's illegal, maybe selling it exposes the other person to risk), you can not simply hand him the money and have him hand you the goods. So you set up an arrangement: the two of you will never meet or speak, but every week at the same time you will leave a bag under the old stone bridge with money in it, and he will leave a bag behind the mill with the goods in it.

Again, you have a choice. You can leave the money or you can leave an empty bag. He can leave the goods, or he can leave an empty bag. If you leave and empty bag and he leaves the goods, bonanza! That week you got the goods for free. If you leave money and he leaves an empty bag, suck! You lose the money. If you both leave empty bags, well, you still have your money, but what you really wanted was the goods. And so on.

Knowing that you will be repeating this transaction every week changes the situation a bit. Do you always leave the money? Sometimes leave money and sometimes leave an empty bag?




Gilovich, who is a psychology researcher, has run Prisoner's Dilemma problems on a large number of volunteers, and writes about the trends he's noticed. People who naturally tend to be cooperative spot that tendency toward cooperation in others, especially during iterative Prisoner's Dilemma problems, and quickly adopt an all-cooperation policy. Every week they leave the bag of money, every week the other player leaves the bag of goods, and everyone is happy.

On the other hand, people who tend to defect--to turn against the other player--will force cooperative players to start to defect themselves, out of self-preservation. If the other person leaves you an empty sack two weeks in a row, you're likely to stop leaving money in your sack, simply because you no longer trust the other person. In other words, his actions have made you begin playing a defecting strategy, even though your desire was to play a cooperative strategy.

This is actually a post about polyamory. Hang on, I'm getting to that.




Gilovich writes that people who start off adopting defecting strategies tend to have a world view that says other people are basically bad, the world is basically an evil place, others are motivated by selfishness and greed, and people on the whole generally suck. This world view is then confirmed by the fact that all the partners they play the game with defect, and start leaving empty bags. In other words, he says, a Prisoner's Dilemma strategy of defecting against the other player is rooted in a self-fulfilling prophesy. You go into the game believing that the other player will defect, so you start out by defecting, and then--surprise!--the other player starts to defect. Even if his impulse was to cooperate. Your actions created the situation you expected, and thus, your view that the world is a hostile place is confirmed.

The connection between a hostile Prisoner's Dilemma strategy and self-fulfilling prophesies was new to me, and naturally, it instantly created a new connection between Prisoner's Dilemma problems and polyamory in my head.




I tend to see a lot of people in poly relationships who are very uncomfortable with the idea of meeting a lover's other lovers. This is among the single most common source of angst I've noticed for people who are polyamorous, especially if they're fairly new to polyamory.

Meeting a lover's other lover presents a host of opportunity for cooperation or defection. You can reach out to the other person and try to make that person feel welcome; you can be closed up and defensive to that person; you can even be actively hostile to that person. And, of course, your lover's lover has similar choices.

Reaching out to someone makes you vulnerable. If two people both reach out to one another, then things will tend to go more smoothly; but if one person reaches out and the other is defensive or hostile, the consequences for the person who reaches out can be pretty dire. A strictly rationalistic approach might suggest that the best strategy is to be defensive, because if you're defensive, you have nothing to gain but nothing to lose either, whereas if you reach out, you might gain something--but you might lose a great deal, as well.

And there's no question that your expectations about the other person, and your behavior upon meeting that other person, can easily become a self-fulfilling prophesy.

Suppose you start out, prior to the meeting, by believing that your partner's new love is a conniving, self-centered bitch (or bastard), determined to undermine your relationship and to take your partner away from you. If you go into your first meeting with this belief, I guarantee it's going to show. Your partner's other partner is going to be able to tell that you don't trust him (or her), that you're looking for reasons to dislike him (or her). So that person is likely to behave defensively, even if the first impulse might otherwise have been to reach out to you. You look at the defensive reaction, and say "See, look! I told you this person was bad news!"

And that's before we even get to the issue of confirmational bias, which is a whole 'nother can of worms altogether.




So are we left, then, with the grim conclusion that the only rational way to meet a lover's new lover is to be defensive, even knowing that this defensiveness is likely to trigger the very thing we believe we're defending against?

Thankfully, no.

In 1980, a pair of researchers studying Prisoner's Dilemma problems sponsored a tournament. Attendees were invited to write computer programs that played iterative Prisoner's Dilemma games against each other. Each could use whatever algorithm the attendees liked. The goal was simple: maximize one's profits.

ow, at first blush it might seem that an all-defect strategy is the best way to do this. Problem is, if everyone adopts this strategy, then nobody profits at all. So people submitted a number of strategies, some of them very complex. Start out cooperating, then start defecting if the other program cooperates, and you'll get the booty for free. Or cooperate much of the time, but randomly defect. Some programs attempted to analyze the other programs, looking for patterns in their moves and then computing a strategy for maximizing profits against those patterns.

In the end, the program that won, consistently, was also one of the simplest. It employs a basic strategy that can be summed up in the words "cooperation" and "forgiveness," and it goes by the name "Tit for Tat."

Tit for Tat is an incredibly simple approach: On the first round, cooperate. On each additional round, do whatever your partner did last time. If your partner cooperated, continue to cooperate. If your partner defected, defect, then see what your partner does this round; if your partner's defection was a one-time deal and he cooperates, go back to cooperation.

This is an amazingly resilient strategy. Against a player who defects all the time, it defects all the time; against a player who always cooperates, it cooperates. Against a player who occasionally defects, it occasionally defects, but it doesn't hold a grudge; if the other player returns to cooperation, it returns to cooperation. Simple as it is, in iterative Prisoner's Dilemma problems, it's virtually unbeatable.




That's a good strategy for life, too. I've seen, and been involved in, relationships that were wrecked because one partner entered a relationship with another partner from an attitude of suspicion and mistrust, and then created the same suspicion and mistrust in the other partner. Tit for Tat shows that when we start from a spirit of cooperation, we both come out ahead; winning does not need to be done at the other person's expense, and indeed, in an ongoing relationship, there is no winning at the other person's expense. Either both players win or both players lose.

Tit for Tat is not naive; if the other person defects, so does Tit for Tat. But Tit for Tat doesn't hold grudges either; if the other person then begins cooperating, then Tit for Tat does, too. Forgiveness is simply sound strategy.

In a very literal sense, you make the social environment you live in. People take their cues from you. Even in a world of people who adopt a hostile, defecting strategy, it is possible to do well. On your first move, cooperate. Open yourself. Invite this other person into your life. Only if it is not reciprocated--only then do you become defensive, and stay that way only for as long as the other person is defensive.

Sometimes, it's the simplest approaches that work the best.


Comments

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sweh
Apr. 16th, 2007 01:23 am (UTC)
I'm not sure the prisoner's dilema is a good model for meeting the partner of a partner because there is another data point in the evaluation of alternatives; if you try to reach out to the other then you will be trying to make your partner happy, and that's always a win irregardless of the response.

Or maybe I'm just naive :-)

I think, really, you're touching on a point you've written about before... jealousy and insecurity; why would someone go into such a meeting thinking the other is trying to steal the partner unless there was insecurity?
tacit
Apr. 16th, 2007 01:29 am (UTC)
Insecurity tends, too, I think, to be a self-fulfilling prophesy (secure partners are more desirable, at least to me, than insecure partners).
eisenfaust
Apr. 16th, 2007 01:44 am (UTC)
A really insightful post, thanks! I have kind of a facination with Games Theory, and Prisoner's Dillema is always a neat subject. I'm not actively poly (I found your journal because of that awesome knotless rope-harness post), but my... something (I wont call her my ex because we're still really good friends and our relationship hasnt changed much, its just no longer the primary focus of our lives) and I had kind of an open relationship. It worked out to be quite rocky.

She was bisexual, I'm not (well, not as much as she is :P). So she, and to some extent I, were always keeping an eye out for girls who would be into us on an emotional, mental, and sexual level. Worked great a few times, until we met a girl who was way more into me than she was into my then GF. GF got very jealous, even though I kept contact between me and the other girl to purely-social stuff (unless all three of us were together, at which time my then-GF and the other girl both got kind of worked up, about me and about eachother)..

It was all very complicated, I was constantly playing the cooperation side of the dillema game. Thats my nature. It was the other girl's nature, too. But Nicole (may as well use her name) was totally and completely unpredictable, within the sums of a prisoners dillema game. So after a few months, defecting became the only reasonable option to avoid continuing to get hurt, and well, that was the end of that phase of things. -_-
tacit
Apr. 17th, 2007 06:34 pm (UTC)
She was bisexual, I'm not (well, not as much as she is :P). So she, and to some extent I, were always keeping an eye out for girls who would be into us on an emotional, mental, and sexual level. Worked great a few times, until we met a girl who was way more into me than she was into my then GF. GF got very jealous, even though I kept contact between me and the other girl to purely-social stuff (unless all three of us were together, at which time my then-GF and the other girl both got kind of worked up, about me and about eachother)..

That happens so often in poly relationships it's not even funny, for reasons that are, once you've been through a few poly relationships, completely predictable. It's common for relationships among three people to grow differently and unevenly, and when that happens, if one person isn't feeling secure, jealousy is often the result. However, the problem is compounded by trying to address the jealousy in a structural way, by changing the nature of the interactions between the other people; the idea that the jealousy can be "fixed" by passing rules saying things like "no contact unless I'm there" looks good on paper but doesn't actually work.

Bad situation all the way around. I'm sorry.
ivymcallister
Apr. 16th, 2007 01:50 am (UTC)
Forgiveness is simply sound strategy. (...snip...) Open yourself. Invite this other person into your life. Only if it is not reciprocated--only then do you become defensive, and stay that way only for as long as the other person is defensive.

That's as may be, but there's something to be said for backing far enough away that nothing else can happen that will require forgiving. Awkward though it may be for the partner caught in the middle, sometimes you have to know when to quit, and that--knowing when to stop reaching out--is the hard part. You can spend the rest of your life thinking, "Maybe if I'd just (done thus-and-such) ..." or you can keep trying and continue risking drama and hurt feelings.

The down side of backing off is that once one has moved far enough away that they are out of harm's reach, they're also so far removed that they're unlikely to be aware of any overtures toward cooperation.

If I'm far enough away that I can't hear you yelling insults, I certainly can't hear you whisper, "I'm sorry."

Someone has to be prepared to step outside the margins of safety, and it's unlikely to be the original defensive party. If one party really wants it to work out, I think they have to be resigned to stepping into harm's (or hurt's) way from time to time to see if anything has changed. Or just to let the other person know that the opportunity for peace exists. It's always a risk, but waiting for someone else to change is often an exercise in futility.

...but if one person reaches out and the other is defensive or hostile, the consequences for the person who reaches out can be pretty dire.

I learned that one the hard way.
tacit
Apr. 17th, 2007 06:37 pm (UTC)
If I'm far enough away that I can't hear you yelling insults, I certainly can't hear you whisper, "I'm sorry."

Very true. In fact, the book even talks about that, in the context of how negative or critical assessments of other people seem more often to be rewarded than positive or optimistic assessments of people. If one starts with a negative assessment of another person, that other person often will never have the opportunity to prove the assessment wrong, whereas if one starts with a positive assessment of another person, that other person is given plenty of opportunity to screw up.

I definitely believe on giving people the benefit of the doubt, though, because I believe my life is more enriched by keeping good people close than keeping bad people away. If someone I let close turns out to be harmful or destructive, I can always change my assessment, but if I start out thinking of someone as harmful or destructive, I'll never get the chance to change my assessment. :)
6_bleen_7
Apr. 16th, 2007 01:55 am (UTC)
I have nothing substantive to add; I just wanted to say there cannot possibly be a better name than "Tit for Tat" for a strategy for approaching poly relationships. : )

Douglas Hofstadter wrote extensively about the Prisoner's Dilemma and related "cooperate/defect" strategies in Metamagical Themas, an expansion of his column for Scientific American back in the 80s, in which he develops ideas in the column in retrospect and in the light of feedback from perceptive readers. Twice he talked the magazine into donating money for social experiments. In the first, he asked about 20 educated people he knew to play a multiway Prisoner's Dilemma. If everyone cooperated, then everyone would benefit the most in aggregate (winning, if I recall correctly, US $57 each); but anyone happened to be the sole defector would benefit enormously at everyone else's expense. And no matter how many defected, defectors would always earn more money than cooperators. Moreover, Hofstadter requested each of the players to explain the reasoning behind his or her decision. In the end, about two-thirds of these learned people—most of whom had doctorate degrees—defected, for reasons I found either lame or fascinating.

Hofstadter, for his second experiment, invited readers to enter in a lottery. The prize was US $1 million divided by the number of entries. People could submit more than one entry, with no limit: each contestant simply wrote the number of entries on a postcard and sent it in. Clearly, the idea was to mail in a small number of entries—at most 1—so that the prize would still be significant after everyone had responded. Some readers decided that the optimal number of entries per person was less than 1: they computed the probability with which they should send in one entry, as opposed to zero, rolled a die, and took the proper action. Hofstadter, therefore, received a few postcards saying "zero" along with explanations of the rationale behind refusing to enter. Unfortunately, a fair number of jokers went to the opposite extreme, submitting imaginably large numbers of entries (for example, filling a whole postcard with 9s or applying the factorial function hundreds of times to the number 9), so as it happened, the prize to be awarded was so infinitesimally small that there was no point in drawing for the winner.
tacit
Apr. 17th, 2007 06:39 pm (UTC)
I actually have a copy of Metamagical Themas on my bookshelf; it was my first introduction to Prisoner's Dilemma problems. I started out reading Godel, Escher, Bach (and have loaned out that book and never gotten it back so many times that at this point I've bought half a dozen copies), and jumped all over Metamagical Themas when it was published. Good stuff!
sebab
Apr. 16th, 2007 02:09 am (UTC)
It's funny you should mention game theory in this context. A past partner made very similar observations, as he had begun dating two of us simultaneously -- told said he figured my knowledge of game theory (actual and intuitive) would lead me to behave cooperatively at first, admitted worry in the other case. In fact she and I sought each other out and had a few pleasant interactions... so that when HE did a poor job of juggling the two new relationships and both ended, she and I remained reasonably friendly.

I don't know whether that means the warden shouldn't discuss the Prisoner's Dilemma with the actual prisoners, the prisoners really shouldn't get involved with the warden, or that the warden shouldn't be discussing concerns about one prisoner with another despite her being a good risk as a confidante.

Or maybe it means that they'll let just *anyone* be a warden these days, sheesh.

:D

(amazingly enough, there are actually no veiled references to kinky warden-and-prisoner role-playing above -- that's sort of a shame, actually)
tacit
Apr. 17th, 2007 06:40 pm (UTC)
...so that when HE did a poor job of juggling the two new relationships and both ended, she and I remained reasonably friendly.

There is no justice in the world, but there is irony...
(no subject) - joreth - Nov. 23rd, 2007 07:12 am (UTC) - Expand
creekracer
Apr. 16th, 2007 03:04 am (UTC)
re: prisoner's dilemma
Excellent post. I was first introduced to the dilemma last winter through Carl Sagan's Billions and Billions. I'd forgotten about it; your post got me thinking again.

My personal tendency is not so much to defect but to risk nothing when meeting new people, whether they're openly pleasant (cooperation) or difficult (defection). As you noted, such a strategy consistently gets a body nowhere. I lose nothing, which is good, but I gain nothing too. The point of this revelation is not to seek relationship advice. I know my strategy isn't helping me. The point is I know how I got to develop it—the same way everyone does. What does the Prisoner's Dilemma teach us? If one player tends to defect most of the time the other player will, if he's smart, defect most of the time as well.

In my life I've tended to cooperate. My mentors taught me the Golden Rule, which teaches that I should cooperate all the time, regardless of how often my opponent defects. People tended to take advantage of this. After some time I felt foolish. I began not, as I said, to defect, but simply to risk nothing (this works against me after a few hands of Texas Holdem). It’s occurred to me, after reading this post, that a lot of people develop my "risk nothing" strategy in the same way. They begin with the Golden Rule, find that their opponents exploit said rule more than any other, and end up disillusioned and embittered. Just look at the biggest, baddest cities in the world, where you can pretty much expect everyone you meet to immediately defect, to take advantage of consistent cooperation, etc. Defection incites defection.

The only viable solution, it seems, is the Tit for Tat strategy. My question, since I’ve not actually done the research, is does Tit for Tat work well in an environment, such as the aforementioned big, bad city, where most people tend to defect all the time? They defect, you defect, and you continue to defect until they cooperate. But if they never plan on cooperating, everyone, including you, continues to defect all the time. Will the Tit for Tat fellow eventually become as embittered as his opponents?

P.S. There’s a Prisoner’s Dilemma game at http://www.princeton.edu/~mdaniels/PD/PD.html, with commentary and background.

P.P.S. Thanks again for the post. This topic is so engaging I've posted a copy of this reply in my own LJ to see what my friends have to say (likely nothing; replies are sparse these days).
tacit
Apr. 17th, 2007 06:42 pm (UTC)
Re: prisoner's dilemma
The only viable solution, it seems, is the Tit for Tat strategy. My question, since I’ve not actually done the research, is does Tit for Tat work well in an environment, such as the aforementioned big, bad city, where most people tend to defect all the time? They defect, you defect, and you continue to defect until they cooperate. But if they never plan on cooperating, everyone, including you, continues to defect all the time. Will the Tit for Tat fellow eventually become as embittered as his opponents?

Since an all-defection strategy is the only effective one against a player who defects all the time, there's nothing unreasonable about defecting constantly against a person who always defects. The trick is to not let it poison your attitude about people you haven't met yet...which, I concede, is not an easy thing to do.

I solve the problem in part by refusing to continue to play with people who always defect.
james_the_evil1
Apr. 16th, 2007 07:46 am (UTC)
This reminds me, I just ran across a great piece on "wishful thinking" where people willfully disreagrd evidence that disagrees with a conclusion they want to reach in context of religion that I must forward to you
datan0de
Apr. 16th, 2007 11:15 am (UTC)
Any chance you can forward that link to me as well?
(no subject) - james_the_evil1 - Apr. 16th, 2007 03:44 pm (UTC) - Expand
nixicat
Apr. 16th, 2007 09:55 am (UTC)
Hmmm...

I was already very familiar with iterative prisoner's dilemma scenarios, but they don't change my approach to poly very much. I don't think it is entirely reasonable to map the strategy of the simple programs against the almost infinitely more complex vagaries of human behavior.

The programs in question are working on a very small set of information, namely, how did the partner behave in the last (or even last couple), trades. Further, the experiment discussed what is the best average strategy to use, based on aggregate data. Tit for Tat and Tit for Two Tats performed best over the long run, in a closed system, populated with a finite number of other strategies. Also, the rewards and punishments remain fixed in the experiment, where in life, they can vary widely. Real life is just so much more dynamic than the Prisoner's Dilemma can ever begin to model.

Choosing not to defect on small reward opportunities while establishing trust allows scammers to set up a situation where they get to walk out with a big pay off. Exclusive access to a mate can be a very big pay off, and many a newcomer into a poly relationship has disrupted its dynamics enough to make off with that reward. While it is counterproductive to assume bad intentions for new participants, it is equally foolish to extend trust too freely.

If Tit for Tat were such a universally rewarding strategy in real life, we wouldn't need modern research to tell us so. Simple approaches can work best, but oversimplification can result in a theory that sounds great and leaves your heart and home broken.
tacit
Apr. 17th, 2007 06:47 pm (UTC)
Choosing not to defect on small reward opportunities while establishing trust allows scammers to set up a situation where they get to walk out with a big pay off. Exclusive access to a mate can be a very big pay off, and many a newcomer into a poly relationship has disrupted its dynamics enough to make off with that reward. While it is counterproductive to assume bad intentions for new participants, it is equally foolish to extend trust too freely.

Of course, there's one easy solution to that problem: I don't get involved romantically with people who aren't already poly. :) One of the advantages of real-world scenarios is that you do have more information; you can look at the way a person has behaved in the past, and use it to model how that person may behave with you. (Doing this has its own risks; it's important to remember that people can and do change, and past activity is not necessarily an indicator of future performance.)

If Tit for Tat were such a universally rewarding strategy in real life, we wouldn't need modern research to tell us so.

Actually, I don't think that's true. The results produced by Tit for Tat were surprising, even to researchers already extensively familiar with cooperative strategies--and once they were known, they filled in a lot of gaps in fields from economics to evolutionary biology.

We tend to assume that complex behaviors have complex causes and simple behaviors have simple causes, and for that reason, sometimes simple behaviors with complex effects are completely non-intuitive to us. The success of a strategy as simple as Tit for Tat is wildly nonintuitive, so it isn't surprising that such an effective strategy would go unnoticed for so long.
sarahmichigan
Apr. 16th, 2007 03:09 pm (UTC)
Thanks for the book suggestion. I'll put it on my "To Read" list.
onesoul
Apr. 16th, 2007 03:32 pm (UTC)
this is a glorious post. thank you thank you thank you... I love when you bust out with stuff like this.. my favorite kind of yours!!!
merovingian
Apr. 16th, 2007 05:09 pm (UTC)
Another beautiful post, as always, and some really interesting insight. Linking Prisoner's Dilemma to Confirmational Bias, applying it all to poly. Yep, totally.

And I'd like to say, too: thanks for starting cooperative!
merovingian
Apr. 16th, 2007 05:13 pm (UTC)
I'd also like to point out that there's a similarly-named but very different strategy, where everybody just gets their personal strategy inked permanently into their left breast, so that we all act with complete information. It's called Tat for Tit.
indywind
Apr. 16th, 2007 06:11 pm (UTC)
Prisoner's Dilemma maps effects of 2 people's decisions. Poly relationships typically involve at least 3 people's decisions. Would you care to describe a Prisoner's Dilemma type scenario for 3 players? or more?
I think it begins to need advanced mathematics to describe the possible solutions.
tacit
Apr. 17th, 2007 06:50 pm (UTC)
You can always break down more complex interactions to interactions between pairs of people.

Yes, it's true that a group dynamic has a character independent of the individual interactions between every two people. I wouldn't use a Prisoner's Dilemma metaphor to try to describe an entire polyamorous relationship; that's why I'm keeping it limited here to a strategy of openness vs. defensiveness when meeting a partner's other partner for the first time. In such a case, the "cooperate" and "defect" choices seem pretty straightforward to me.

Now, a person might choose a cooperative or defecting strategy based on a number of factors, including the effect it will have on that person's partner, but in the end, either you extend a welcome to the other person or you don't.

One can argue that a person's partner can do things which tip the scales, but if your partner is doing something like deliberately sabotaging your relationship with his other partner, well...in that case, you have other things to worry about. :)
eponasr
Apr. 17th, 2007 12:09 am (UTC)
I'd be very interested to see if someone could do a mathmatical model of the Prisoner's Dilemma but also factor in a "learning curve" so to speak. In other words, introduce a bias depending on how many times a player has been defected upon or cooperated with in the past.
tacit
Apr. 17th, 2007 07:00 pm (UTC)
There have been programs that attempt to do this, but in competitions they tend not to do as well as simple Tit for Tat.

But, interestingly, where that DOES make a difference is when the communication is "fuzzy," and the programs are not given perfect information. There's a variant of the competition where there is a very small, random chance that a program will misunderstand the other program's move, and believe the other program defected when it cooperated (or vice versa).

In this situation, Tit for Tat can get locked in a "death spiral."It believes, erroneously, that the other program defected, so it defects; the other program sees this defection, and defects itself; Tit for Tat sees this defection, and defects; and so on. Programs that are smarter, and play strategies that account for the opponent's past behavior, don't tend to death-spiral when they see one uncharacteristic defection. In a situation with imperfect communication, "tit for two tats" actually works better.
(no subject) - nornagest - Apr. 20th, 2007 06:36 am (UTC) - Expand
(no subject) - tacit - Apr. 20th, 2007 07:30 am (UTC) - Expand
peristaltor
Apr. 17th, 2007 01:16 am (UTC)
I haven't heard anyone (other than myself) mention Tit for Tat since I read an article about it back in 1980. I've been harping on it as an example of cooperative behavior ever since. Geez, 27 years, you'd think others would have found that interesting.

I also like the fact that it was also the shortest code of all the participants, IIRC only four lines of Basic.
tacit
Apr. 17th, 2007 07:03 pm (UTC)
Tit for Tat is a remarkably powerful idea, and I've seen everyone from evolutionary biologists to behaviorists use it to explain the spontaneous emergence of cooperation in competitive environments. Where it sadly gets little attention and could probably use more exposure is in the political arena; I sometimes wonder what a "tit for tat" foreign policy would look like. It certainly could not be less effective than whatever it is we're using now ("tat for the hell of it?"), and would probably, I suspect, work rather a lot better.
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