Hawks, Doves and Dice

In class today we looked at the Moran Process. We did this by considering the Hawk Dove game.

You can see a recording of this here: cardiff.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=f41045d7-ff4b-4e0d-8adb-afbc00d6f23c

The Moran process is a game theoretic model of evolution. One of the differences from the Replicator Dynamics equation is that the population is assumed to be finite: so we assumed there is a finite population of \(N)) individuals that can be of any of the types that correspond to actions of the underlying Norma Form Game.

In the example of the Hawk Dove game that we played in class we assumed there were \(N=3\) individuals and the question we attempted to understand was: if we introduce a Hawk in to a population of Doves, what will happen?

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The Moran process then follows the following:

1. Calculate the fitness of all individuals: everyone in the population plays the Normal Form game against everyone else. Their utility (or fitness) is given by their type and the type of the individual they play with.
2. Randomly select an individual for copying proportional to their fitness.
3. Randomly select an individual for removal (all individuals are equally likely to be removed).
4. Create a new individual of the same type as the one selected in step 2.
5. Remove the individual selected in step 3.

Repeat that process until there is a single type of individual in the population.

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In class we used dice to simulate the above. We were a bit short on time at the end so not everyone got to complete a simulation. We did still find a probability of 67% of the Hawk taking over.

I ran two other numerical simulation (the last one using Nashpy) and found a good approximation around 55%.

In class on Tuesday we will discuss how we can calculate the theoretic value.

You can find a notebook with the various numerical simulations here.

Note that while the game we used here assumes only two type, this is not a constraint of the Moran process.