Evolution of Cooperation

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Evolution of Cooperation

• John Lazarus
• Division of Psychology
• with
• Peter Andras
• School of Computing Science
• and
• Gilbert Roberts, Division of Psychology

2
One of our questions . . .

• Why does cooperation increase under conditions
  of adversity and uncertainty?

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Adversity

• Mean environmental quality
• Resources
• Predators, parasites, competitors
• Abiotic factors
• temperature, humidity, windspeed, altitude,
  substrate quality, pH

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Cooperation increases under Adversity
Alpine plants more cooperative than Sub-alpine
Altruistic stalk in Slime Mould supports fruiting
body
Nematodes feed socially in response to aversive
stimuli
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Cooperation increases under Adversity
Animal groups larger under predation risk
Human in-group solidarity increases under threat
or stress
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Cooperation enhanced under Uncertainty
Human foragers share only unpredictable foods
Money acquired as windfall more generously shared
Communal fisheries grazing commons more
successful under environmental uncertainty
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Explanatory Model

• Adversity increases subjective uncertainty of
  resources
• Analytical result
• Resource uncertainty enhances cooperation
• Multi-agent model
• Thus
• Adversity ? Resource uncertainty ? Cooperation

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Evolutionary Multi-Agent Model

• Prisoners Dilemma game theory model
• Agents
• Spend resources on living costs and to generate
  new resources
• Live in a two-dimensional world
• Have probability of cooperation with another
  agent
• Randomly choose interaction partner from
  neighbourhood and partners decide to cooperate or
  compete
• Produce offspring asexually
• Offspring
• Inherit parents inclination toward cooperation
• Number depends on parental resources
• Resource uncertainty
• Variance of resource distribution that determines
  new resources of agents after interacting

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Simulation Results
Proportion of cooperation

• Tendency to cooperate
• Uniformly distributed at start
• Subject to natural selection
• Increases with uncertainty

high
mid
low

• Cooperation dampens variance in resources gained
• Mortality reduced

variance
Time
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Summary

• Adversity ? Resource uncertainty ? Cooperation

Analytical model
Multi-agent model
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End