17.6: Appendix C- Human Behavioral Ecology - The Evolution of Cooperation (Worksheet)
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17.6: Appendix C- Human Behavioral Ecology - The Evolution of Cooperation (Worksheet)
Opening the book…
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The Prisoner’s Dilemma game is a hypothetical game where two players have the option to cooperate with each other or cheat, without knowing what the other player will do. It is based on a situation where two people are arrested for a crime (hence: prisoner’s dilemma). If they both keep silent, meaning that they do not tell the police what they did and cooperate with their partner, each gets limited jail time (let’s say, one year). But if one cheats, by telling the police, and the other one cooperates, by staying silent, then the one who cheats does not go to jail and the one who cooperates gets a long sentence (let’s say, three years). If both players cheat, by telling the police, then both individuals do a moderate sentence (two years). This game has been used extensively to understand when individuals will cooperate and when they will cheat. In this lab, we will use the prisoner’s dilemma game (also known as the Game of Trust) to understand which strategies (cheating or cooperating) are best given particular circumstances, providing insights into the evolution of cooperation.
After playing the game, you will reflect on how this helps us understand human food sharing.
Getting Started
On your preferred device, navigate to: www.ncase.me/trust. Carefully read and follow the directions. Play the first two rounds of the game and then answer the following questions.
When the other player cheats, what option (cheat or cooperate) gives you the best payout?
When the other play cooperates, what option (cheat or cooperate) gives you the best payout?
Explain why this is a “dilemma.”
Iterated Game of Trust
Now play the repeated or iterated game, where you play against five different opponents and each has their own strategy.
How many total coins did you earn against the five different opponents? (Note: This may take several minutes to play each set of games)
How did you decide whether to cheat or cooperate in these rounds?
We now learn that each of the opponents has a strategy. In the chart below, describe the five strategies that you played against. The strategy copycat is also known as “tit for tat.”
Name
Describe Strategy
Hat Type
Copycat
All cooperate
All cheat
Grudger
Detective
Which character do you think will be most successful in a tournament where each player plays all others? Describe your reasoning.
Place your bet by choosing the character you think will win. Observe the results of the repeated games. Did your character win? If not, which character won?
What conditions occurred during World War I trench warfare that allowed for peace?
Evolution
Human Behavioral Ecologists are interested in the evolution of behavior. Specifically, they seek to learn how trust and cooperation evolved, particularly when there is an advantage to cheating. Let’s observe how things change when our characters are allowed to evolve – meaning that successful players reproduce and unsuccessful players are eliminated.
Describe how this relates to the concept of Natural Selection.
Who do you think will win the first tournament (of Copycat, All Cooperate, and All Cheat)? Explain your reasoning.
What happens when you have All Cooperate and All Cheat in the same tournament?
Which strategy “inherits the earth” or becomes the only strategy remaining after many rounds of the tournament?
Now add Grudger and Detective back in: Which strategy “inherits the earth”?
The Evolution of Distrust
Now we will change the game to adjust the number of rounds our characters play. In the table below, document which strategy wins under each of these conditions.
Number of Rounds
Winning Strategy
10
Copycat
7
5
3
1
Explain why the winning strategy changes at fewer numbers of rounds.
What happens when the “both cooperate” payoff is changed from +2 to +1? Note: You need to adjust the payoff values and then click “Start”.
Explain why this changes the optimal strategy.
What happens if you change the payoff for cooperation by increasing its value?
What is a “Zero-sum Game” and a “Non-Zero-Sum Game”? Why does it matter if you are playing a zero-sum versus. non-zero sum game?
Mistakes
How can honest mistakes affect the game?
Click “…deal with mistakes” In the table below, describe the new strategies.
Name
Describe Strategy
Hat Type
Copykitten
Simpleton
Random
Who do you think will win if they play in a tournament? Explain your reasoning.
Who do you think will win if the population of players includes All Cheat instead of All Cooperate? Explain your reasoning.
Now we can adjust the frequency of mistakes to see if that influences the best strategy for a population that includes All Cheat. Fill out the following table:
Percent of Miscommunication (or mistakes)
Winning Strategy (Note: This strategy may change depending on the randomness in the simulation. Also, it’s possible for two strategies to remain)
5%
Copykitten
0%
1%
10%
25%
Optional: Sandbox Mode
If you would like, you are welcome to play in the sandbox mode to further understand how different starting populations, payoffs, and rules influence winning strategies.
Conclusion
25. Based on this activity and the reading, name and describe three key issues impacting the evolution of altruism and trust?