So now that I have my few lines of Python written, I obviously want to have a play with it. What would happen if instead of playing Iterated Prisoner’s Dilemma, they were playing Rock Paper Scissors?

There’s no iteration here, and no chance to choose a “mixed” strategy (e.g. randomly choosing each with 1/3 probability). Just three strategies: rock, paper, scissors.

So I figured: either it’s going to go around in cycles, or converge to a point where each strategy is stuck at 1/3. Since the problem feels time-reversible I’d expect cycles. And what do we get?

(By the way, you can see them gradually spiralling outwards but I think that’s a numerical modelling issue – the discrete time steps are going to mess things up a bit).

So the next obvious question is, what about Rock Paper Scissors Lizard Spock? In case you’re not familiar, the payoffs look like this:

Rock | Paper | Scissors | Lizard | Spock | |

Rock | 0 | -1 | 1 | 1 | -1 |

Paper | 1 | 0 | -1 | -1 | 1 |

Scissors | -1 | 1 | 0 | 1 | -1 |

Lizard | -1 | 1 | -1 | 0 | 1 |

Spock | 1 | -1 | 1 | -1 | 0 |

And what happens when you play them against each other in my natural selection model?

## 0 Responses to “Just a bit of fun: rock-paper-scissors”