The prisoner's dilemma inspires so many interesting thoughts ...

- it's the classic example of GameTheory

- it's a scientific
*pattern*. Something which explains, but isn't quite a law (See also TheScientificStatusOfPatterns)

- it reveals that not all games are zero sum, we can benefit from co-operation

- it reveals that local self-interest
**doesn't**always add up to the greatest good

- it can explain the evolution of society

- it can explain the evolution of the individual (Maybe. See
*PhilsAcademicResearch*)

### Don't be confused

People often give over-simplified, garbled accounts of the prisoner's dilemma. Let's try to set the record straight.

**The prisoner's dilemma does NOT prove that altruism is better than selfishness **

The fact that mutual co-operation scores higher than mutual defection is an *axiomatic assumption* of this model. Of course, the fact that we find it worth applying this model to the world, demonstrates that yes, there are situations where co-operation is better than competition. But we need to see (or hypothesize) these before we start using the model. When we apply the PD we are basically starting with the hypothesis that here is a situation (eg. predator inspection by sticklebacks) where there two things are the case :

- mutual co-operation is advantageous to mutual defection

- there is the possibility of and incentive for cheating (ie. not reciprocating help given earlier)

If the PD fails to be a good model then maybe one of these assumptions is wrong for this situation. If not, the have some sort of corroberation.

**The prisoner's dilemma does NOT show that, phew!, humans are really altruists after all and not selfish.**

In fact the straight (one-shot) prisoner's dilemma is a situation where defection is the only rational strategy. All interesting work is done with the *Iterated* Prisoner's dilemma".

The role of the IPD in evolutionary biology is the opposite of what you might expect. It doesn't beatify animals, it **saves** Darwinian evolutionary theory from the embarassment of not being able to explain altruistic interactions between non-relatives. Without a suitable explanation, a Darwinist wouldn't be able to explain the observations of altruistic behaviour and we'd be seeking some other explanation.

### PD LinkBin

- CosmaShalizi on various "improvements" on
*TitForTat*: http://cscs.umich.edu/~crshalizi/weblog/275.html

*Backlinks* *(1 items)*