[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

The Prisoner's Dilemma



New in _The American Naturalist_:

  Killingback, T. and Doebeli, M. 2002. The continuous prisoner's dilemma
  and the evolution of cooperation through reciprocal altruism with
  variable investment. _The American Naturalist_ 160 (4): 421-438.

  You think the title explains it all? Flowery? No. Concepts on the
development of cooperation in organisms have involved largely behavioral
models that have never been corroborated or mathematical experiments that
indicate probabilities of results. Essentially, the paper involves the
prisoner's dilemma (hereafter referred to as PD) and an essential "game"
method of determining how the origin of cooperation can be observed. PD is
essentially a paradox, a conflict between altruism and selfishness. To any
individual during the evolution of life, selfishness has been the primary
focus in survival, basic Darwinian concept of survival of the fittest; it
is therefore most advantageous to an individual to be selfish. Yet still,
cooperative groups have developed over several methods (detailed in the
paper and referencesd further) in spite of this selection advantage to the
selfish creature; cooperative associations increases the benefit over
multiple people versus a single individual, and permits families, for
sake, to persist versus one individual. PD is intriguing because it
supports the selfish scenario, and indicates selfish creatures will cause
any cooperators to be eliminated from the field.

  It works like this:

  There are two players, the prisoners. There are two attitudes, C for
cooperator, and D for defector; there are four playable states: T for
temptation to cheat, R for reward for cooperation, P for punishment for
defecting, and S for cooperating against your opponent, or the sucker's
payoff. Each state has a value resulting in the following series: T > R >
P > S, depending on individual benefit. In this, the first player is
assumed to play the defector (D), and thus would pick T > R, and P > S.
But so is the second player. The authors described mathematical
perambulations that permit a different outcome with the same basic design,
building on the same principles and data, which I will not go into too
much detail; furthermore, their results include mathematical models that
permit a cooperative system to arise from a selfish one, and permit any
organism to become cooperative. This draws upon previous models including
the "tit for tat", "generous tit for tat", and "pavlov" systems, each
which permit the players to be able to eventually arrive at a cooperative
state, but with constant checks to affirm outcomes. The authors introduce
the "continuous iterative prisoner's dilemma" which is itself a solution
that does not require any checks, and as the title states, it is based on
reciprocal altruism not dependant on continuous investment, but will
arrive at the end state no matter the investment. It a great paper, the
title grabbed me because of recent discussion on cooperative hunting, and
I ended up not being able to put it down. Other more accessible papers are
available on the web or can be garned with help (I have provided links to
each item):

  Cited paper above:

  Killingback, T. and Doebeli, M. 2002. The continuous prisoner's dilemma
  and the evolution of cooperation through reciprocal altruism with
  variable investment. _The American Naturalist_ 160 (4): 421-438.
(http://www.journals.uchicago.edu/AN/journal/issues/v160n4/020011/brief/020011.abstract.html
- URL may be clipped, but you may just need to go to the
  root site http://www.journals.uchicago.edu/AN/journal/ and search from
  there)

  Doebeli, M. and Knowlton, N. 1998. The evolution of interspecific
  mutualism. _Proceedings of the National Academy of Sciences, USA_ 95:
  8676-8680.
  (http://www.math.ubc.ca/~doebeli/publications.html or
   http://www.zoology.ubc.ca/~alistair/z/faculty/doebeli.html - scroll
   down, the authors provide a pdf)

  Killingback, T. and Doebeli, M. 1999. Raise-the-stakes evolve into a
  defector. _Nature_ 400: 518.
  (http://www.math.ubc.ca/~doebeli/publications.html or
   http://www.zoology.ubc.ca/~alistair/z/faculty/doebeli.html - scroll
   down, the authors provide a pdf)

  Killingback, T.; Doebeli, M.; & Knowlton, N. 1999. Variable investment,
  the continuous prisoner's dilemma, and the origin of cooperation.
  _Proceedings of the Royal Society of London, B_ Biological Sciences 266
  (1430): 1723-1728.
  (http://www.pubs.royalsoc.ac.uk/ - you will have to access the journal
  listings to the appropriate journal, then archives, then go to volume
  266 and find the listed issue, it will not allow me to link the URL, as
  it is not given)

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com