Notes on Cooperation among Non-Kin II

Cooperation Among Non-Kin II

Problem of Cooperation
  • Key Issues: How can benefits be directed to cooperators rather than defectors?
    • Linking future payoffs to past behavior.
    • Changing the payoff structure.
    • Cooperate with relatives.
Introduction to Game Theory
  • Definition: A mathematical tool to analyze interactions where the payoff for an individual depends on the actions of others.
  • Examples in Animal Behavior:
    • Prisoner's dilemma: Illustrates the conflict between cooperation and self-interest.
    • Cooperative hunting game: Analyzes benefits of group hunting.
  • Strategy: Behaviors are represented as strategies in the game.
Evolutionary Stable Strategy (ESS)
  • ESS Explained: A strategy that, if established in a population, cannot be invaded by any alternative strategy.
    • Mathematical Representation: The system returns to the ESS after perturbations.
    • ESS must yield higher payoffs than any mutant strategy.
  • Key Features:
    • Stability against invasive strategies.
    • Describes how frequency of strategies affect fitness.
    • Example: In the iterated prisoner's dilemma, 'Tit for Tat' is a stable strategy.
Behavioral Strategies in Populations
  • Diversity of Strategies: Populations may exhibit multiple behavioral strategies for various activities (e.g., hunting, defense).
    • Equal Fitness: Different strategies can achieve similar fitness depending on the context.
    • Frequency dependency of strategy fitness affects population dynamics.
Payoff Structures Favoring Cooperation
  • Cheaper Cooperation: Cooperation is more likely when:
    • Costs of cooperating are low.
    • Cheating yields few benefits.
    • High costs are associated with cheating.
Cooperative Hunting Game
  • Game Structure:
    • Cost of hunting = -1.
    • Individual benefit increases with more hunters:
    • Benefit per individual when two hunters = 8.
    • Benefit per individual when three hunters = 18.
    • Free Riding: Non-cooperators benefit from group efforts without incurring costs.
Low-Cost Cooperation
  • By-product Mutualism: Cooperation provides mutual benefits without direct costs.
  • Example: Group size influences hunting success, leading to cooperative strategies.
Partner Choice and Social Learning
  • Selection of Partners: Individuals may select partners based on quality or past interactions, which influences cooperative dynamics.
  • Social Learning: Potential costs exist for demonstrators who teach others, creating competition for resources.
  • Kin Selection: Cooperation is often higher among relatives, enhancing inclusive fitness.
Partner Sanctions
  • Conditional Rewards: Rewards provided by one partner may depend on the contributions of others, discouraging opportunistic behavior.
  • Enforcement Mechanism: Partners can sanction cooperative behaviors by reducing investment or terminating interactions to maintain cooperation.
Ultimatum Game
  • Structure:
    • Player 1 decides how to split 100 “Animal Behavior dollars” with Player 2.
    • Player 2 decides whether to accept the offer.
    • Typically, offers below 30% are rejected, indicating a societal norm against unfairness.
Summary of Payoff Structure Improvements for Cooperation
  • Changes in Payoff Matrix Leading to Cooperation:
    • Decreased cost of cooperating.
    • Increased benefits of cooperating.
    • Increased costs of defecting.
    • Decreased benefits of defecting.
  • Examples: Vampire bats exhibit cooperative behaviors due to both reciprocity and kin preferences.
Challenge Question: Cooperation and Parental Care
  • Discussion Points:
    • Analyze parental cooperation benefits and mechanisms for encouraging cooperation (e.g., choice, sanctions).
    • Investigate conditions under which partner choice is effective and when it may lead to maladaptive behavior.
Conclusion
  • Key Takeaway: Cooperation among non-relatives can evolve through mechanisms that escape the prisoner’s dilemma, such as partner sanctions or by-product cooperation.