From: throopw@sheol.UUCP (Wayne Throop)
Newsgroups: rec.arts.sf.written,rec.arts.sf.science
Subject: Moties and the prisoner's dilemma
Summary: It isn't clear to me whether "always defect" would be stable in moties
Date: 29 Aug 92 22:55:23 GMT

I didn't see the notions of the iterated prisoner's dilemma's impact on
evolutionary thought applied to the question of the Moties and their
cycles, so I thought I'd post a line or two, since the idea seems
interesting.

First, it seems to me that the Moties cycles form an iterated prisoner's
dilemma.  That is, there is enormous payoff in cooperation, but even
more enormous payoff in "defecting".  In a simple games matrix, it is
"obvious" that the "correct" strategy is "always defect" and have as
many children as possible. 

And indeed, this is an evolutionarily stable strategy.  See the second
edition of "The Selfish Gene" by Dawkins, where the notions of the ESS
and the application of this notion to situations like those of the
Moties is gone over. 

But there is a bit more.  The whole point of Dawkins' report of
Rappaport and Axelrod's work on the prisoner's dilemma was to point out
that "altruism" can evolve there.  Note that a suite of strategies of
the "tit for tat" variety are also evolutionarily stable.  But the more
interesting thing is, a stable situation of "always defect" can
(perhaps) be invaded by "tit for tat" strategists, as explained by
Dawkins. 

In the case of the Moties it might work like this.  The "reward for
cooperation" in the cycles is the avoidance or postponement of a crash,
and hence the avoidance of the deaths of many children.  The
"tempatation to defect" is of course the fact that defectors
preferentially "seed" the next cycle.  The consolation prise of mutual
defection and the "suckers payoff" follow similarly. 

Now, how can "tit for tat" strategies invade a stable situation of
"always defect" players? First of all, the "tit for tat" can't retaliate
in the traditional inverse defection, since that'd essentially make
future cooperation difficult, and make the strategy too rigid and
"unforgiving", and further make the reward for cooperation hard to
collect.  But they *can* retaliate in other ways, most obviously the
witholding of trade and other resources from defectors. 

So, Moties can (at least tenatively) play tit-for-tat.  But how can they
realize the reward for cooperation in the face of the upcoming cycle
boundary? I see it this way.  A small group of tit-for-tat (Crazy Eddie)
players have a small window of opportunity just before the turn of the
cycle, where they become more efficient than their always-defect
competitors.  The defectors must spend resources supporting
overpopulation that the cooperators need not.  This payoff works up
until the point where population pressure forces the defectors to attack
the cooperators, turning the cycle.  But at that time, the cooperators
are in a (slightly) better position to defend themselves, having
deployed their resources without a large (that is, with a
slightly-less-large) population to support. 

This would allow the enclave of Crazy Eddies (tit-for-tat players) to
preferentialy seed the next cycle, at least locally, and gradually turn
the tide into the other stable state.  (Dawkins points out that the
reverse strategy-state-change probably wouldn't work, since enclaves
of defecting players don't mutually reinforce.)

Of course, this depends on the payout matrix of "actual" Motie economics
forming a prisoner's dilemma payoff matrix, which is far from certain. 
The fact that I'm handwaving away a swarm of details doesn't make this
notion as persuasive as it might be.  Especially because the PD is a
non-zero-sum payoff matrix, and the Moties may well have reached a point
where all economics is dominated by zero-sum considerations.  But at
least tenatively, we have here a way for the Moties to break out of
their cycles, in an evolutionarily stable fashion (whether genetic or
cultural evolution). 
--
Wayne Throop  ...!mcnc!dg-rtp!sheol!throopw