BIO150Y: Evolution of Cooperation Multiple-Moves Game

Background to the multiple-moves game

What is a Multiple-moves Prisoner's Dilemma Game?
In a multiple-moves Prisoner's Dilemma game you can play against the same partner many times. This simulates mutualistic interactions in social groups where individuals will frequently encounter each other. An example of cooperative behaviour which appears to be a multiple-moves game is mutual grooming for parasites, which many animals do, including chimpanzees.

Cooperate Defect
Cooperate b - c - c
Defect b 0

Cost and Benefits Payoff Matrix
In game theory terms, you cooperate when you groom your partner and you defect if you refuse to groom your partner. Mutual grooming can be thought of in terms of the costs (c) you incur grooming your partner, and the potential benefits (b) you will derive if they reciprocate and groom you back. In general terms then, we can use costs and benefits to define the payoffs as shown here.

Cost-benefit payoff matrix

Your Cost-Benefit Payoff Matrix
Costs and benefits in real terms might be measured in time, survival, or reproduction. So long as the potential benefits of performing the behaviour outweigh the costs, cooperation is possible. For now, let's assign arbitrary values of costs = 2 points and benefits = 4 points so that we can construct a payoff matrix for your game. To simplify the matrix we have adjusted all payoffs so that the lowest payoff is zero (normalized matrix).
Calculate the payoff

Cooperate Defect
Cooperate 4 0
Defect 6 2

"You are now ready to play the game repeatedly against the computer. Good luck!"
First move:

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