Dominance Interactions & Game Theory

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Game Theory

  • Evaluation is via Game Theory
  • Developed by Maynard-Smith, based on economic theory
  • The solution to the 'game' is the evolutionary stable strategy 
    • A strategy which, when adopted by most members of the population, cannot be beaten by any other strategy in the game.

Analysis of Fighting Strategies

  • What is the most successful fighitng strategy?
  • Why are some fights ritualised displays and others physical contact?
  • Evolution should favour displays
  • Strategies can't be evaluated using a simple optimality model of costs and benefits as the optimal way for one individual to behave depends on what other competitors are doing.

Hawks and Doves

  • Imagine a contest over a resource (e.g. habitat) with 2 extreme strategies:
  • Hawk
    • Always fight to injure and kill your opponent - possible risk of injury to self
  • Dove
    • Display but never engage in a serious fight - i.e. run away when opponenet escaltes fight

Fight outcomes

  • Hawk vs Hawk
    • Each contestant has a 50% chance of injuring opponent and winning resource, and 50% chance of being injured.
  • Hawk vs Dove
    • Hawk always wins resource
  • Dove vs Hawk
    • Dove retreats immediately before injury
  • Dove vs Dove
    • Resource is shared

Payoff Matrix

How would evolution proceed?

  • If all individuals were Doves....
    • Everyone has an average payoff of 25
    • But a mutant Hawk has a payoff of 50 so would do very well
    • Dove is not an Evolutionary Stable Strategy as it can be invaded by Hawks

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