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17.3: Appendix C- Human Behavioral Ecology - The Evolution of Cooperation

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  • Page ID
    142410
    • Herzog, Nicole & Snopkowski, Kristin

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    The Evolution of Cooperation

    Format: In-person or online


    Authors: Herzog, Nicole; Snopkowski, Kristin

    Modified from: The Game of Trust www.ncase.me/trust

    Time needed: 75 minutes

    Learning Objectives

    • Define the Prisoner’s Dilemma game
    • Identify the most successful strategy in a one-shot prisoner’s dilemma game and an iterated prisoner’s dilemma game
    • Identify factors that can break down cooperation or trust
    • Explain how the Prisoner’s Dilemma game can help us understand human food sharing

    Supplies Needed

    • Internet access
    • Worksheet (provided)

    Readings

    Introduction

    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, students reflect on how this helps us understand human food sharing behavior.

    Game theory is defined as the study of the ways in which interactions among players produce outcomes. In this case, students play the Game of Trust. Their payoffs are in terms of coins. Each student is represented by the player on the left (the character with the red hat) and they play with a ‘computer player’. If the student cooperates and the computer player cheats, the student loses a coin. If both cooperate, the student earns two coins. If the student cheats and the computer player cooperates, the student earns three coins. If they both cheat, the student earns zero. If the student plays the game once, it’s known as a one-shot prisoner’s dilemma game.

    Steps

    1. Students navigate to: www.ncase.me/trust. It is best if each student has their own device to play.
    2. Let students know that there is a set of circles on the bottom of the screen, if students need to move to another part of the game, they can use the circles to move quickly to the end or beginning of the game. They won’t be marked down for their choices of play in the game. They will only be evaluated based on their answers to the accompanying questions.
    3. Distribute the worksheet and tell students to read the instructions step-by-step as they play and then answer the questions in order.
    4. After they play, discuss the reflection questions and make connections with how this game can help understand human food sharing.

    Reflection Questions

    While the Prisoner’s Dilemma game was not designed to explain food sharing, we can use the game to help us understand the dynamics of trust and cooperation as they relate to decisions about resource sharing within small-scale societies.

    1. Thinking about the Prisoner’s Dilemma game, which factors would you expect to see in a population that engages in extensive food sharing?
    2. Which factors are we unable to account for in the Prisoner’s Dilemma game and how might that limit its application to the problem of food sharing?

    Adapting for Online Learning

    1 Not adaptable 2 Possible to adapt 3 Easy to adapt

    For Further Exploration

    References

    Henrich, Natalie; Henrich, Joseph, 2007. Why Humans Cooperate: A Cultural and Evolutionary Explanation. Oxford: Oxford University Press Inc.

    Snopkowski, Kristin. 2019. “Appendix C: Human Behavioral Ecology”. Explorations: An Open Invitation to Biological Anthropology, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff. Arlington, VA: American Anthropological Association. http://explorations.americananthro.org/

    Tomaselloby, Michael; Dweck, Carol. 2009. Why We Cooperate. Massachusetts: The MIT Press.

    Image Attributions

    Prisoner’s Dilemma icon by Christopher X Jon Jensen (CXJJensen) & Greg Riestenberg is licensed under CC BY-SA 3.0 International.

    Acknowledgement

    Thanks to Nicky Case for developing The Game of Trust interactive website.

    The Evolution of Cooperation Worksheet

    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.

    1. When the other player cheats, what option (cheat or cooperate) gives you the best payout?
    2. When the other play cooperates, what option (cheat or cooperate) gives you the best payout?
    3. 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.

    1. How many total coins did you earn against the five different opponents? (Note: This may take several minutes to play each set of games)
    2. How did you decide whether to cheat or cooperate in these rounds?
    3. 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    
    1. Which character do you think will be most successful in a tournament where each player plays all others? Describe your reasoning.
    2. 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?
    3. 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.

    1. Describe how this relates to the concept of Natural Selection.
    2. Who do you think will win the first tournament (of Copycat, All Cooperate, and All Cheat)? Explain your reasoning.
    3. What happens when you have All Cooperate and All Cheat in the same tournament?
    4. Which strategy “inherits the earth” or becomes the only strategy remaining after many rounds of the tournament?
    5. 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  
    1. Explain why the winning strategy changes at fewer numbers of rounds.
    2. 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”.
    3. Explain why this changes the optimal strategy.
    4. What happens if you change the payoff for cooperation by increasing its value?
    5. 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

    1. How can honest mistakes affect the game?
    2. Click “…deal with mistakes” In the table below, describe the new strategies.
    Name Describe Strategy Hat Type
    Copykitten    
    Simpleton    
    Random    
    1. Who do you think will win if they play in a tournament? Explain your reasoning.
    2. Who do you think will win if the population of players includes All Cheat instead of All Cooperate? Explain your reasoning.
    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

    This page titled 17.3: Appendix C- Human Behavioral Ecology - The Evolution of Cooperation is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Herzog, Nicole & Snopkowski, Kristin via source content that was edited to the style and standards of the LibreTexts platform.