Theory of Selected Cooperation
Cooperation Across Generations
Selected cooperation refers to cooperative behavior that becomes more common through natural selection across generations, rather than through adaptation during a single lifetime.
In this framework, populations:
- contain heritable variation in behavior,
- differ in survival and reproductive success,
- pass on traits associated with higher fitness.
This process corresponds to evolutionary dynamics in biology and to selection over inherited behavioral tendencies in population-level models.
From Adaptive Policies to Inherited Strategies
Classical evolutionary models treat cooperation as a trait or strategy that can spread when it improves reproductive success under specific ecological and social conditions.
Selected cooperation differs fundamentally from learned cooperation:
| Learned cooperation | Selected cooperation |
|---|---|
| Policy changes within lifetime | Strategy frequencies change across generations |
| Learning acts across interactions | Selection acts across generations |
| Reward shapes behavior | Fitness shapes trait prevalence |
| Adaptation is individual-level | Adaptation is population-level |
Thus, cooperation can persist even when individuals are not explicitly "trying" to cooperate, provided cooperative traits are favored by selection.
Evolutionary Dynamics as a Model of Selection
Evolutionary models describe how cooperative and defective strategies change in frequency over time under selection pressure.
Key ingredients include:
- heritability of behavioral tendencies,
- differential reproductive success,
- ecological constraints on survival,
- interaction structure (who meets whom).
Because fitness depends on interactions with other individuals, the evolutionary problem is inherently social.
This creates:
- frequency-dependent selection,
- coexistence of strategies,
- evolutionary cycling,
- context-dependent stable equilibria.
Selected Cooperation in Social Dilemmas
Evolutionary game theory shows that:
- Cooperation can spread when it yields higher inclusive or long-term fitness
- It can be undermined by defectors exploiting cooperators
- Stability often depends on structure, repeated interaction, or assortment
- Population composition changes the payoffs of each strategy
Key mechanisms include:
Kin Selection
Cooperation evolves when helping relatives increases inclusive fitness.
Direct and Indirect Reciprocity
Cooperation can be favored when repeated interactions or reputation make future benefits likely.
Spatial and Network Structure
Limited mixing can protect cooperative clusters from exploitation.
These mechanisms explain how cooperation can evolve without requiring centralized control.
Sequential and Ecological Contexts
In natural systems, cooperation is often embedded in sequences of actions and changing environments rather than one-shot interactions.
This introduces:
- delayed fitness consequences,
- ecological feedback,
- population-level outcomes emerging from local interactions.
Such settings are better captured by ecological and evolutionary simulations than by static matrix games alone.
Selected Cooperation in PredPreyGrass
PredPreyGrass provides a setting to study how cooperative tendencies may be favored by selection when they improve survival and reproduction over generations.
Examples include:
- inherited predispositions for coordinated hunting,
- traits that reduce costly interference,
- selection for timing and spacing that improves capture success,
- plasticity traits that make cooperation easier to learn.
In this view, cooperation is not only a behavioral pattern but also a target of selection on underlying traits.
Instability and Evolutionary Social Dilemmas
Selected cooperation is also often fragile.
Populations can face:
- invasion by defectors,
- shifting ecological conditions,
- tradeoffs between short-term and long-term fitness,
- dependence on population density and assortment.
This leads to:
- cycles between cooperation and defection,
- polymorphic populations,
- collapses of cooperative regimes after environmental change.
Studying these instabilities is central to understanding when selection can sustain cooperation.
Relation to Learned Cooperation
Selected cooperation operates on a slower timescale than learning within lifetimes.
This creates several possibilities:
- Evolution can shape the capacity to learn cooperative behavior.
- Learning can alter ecological conditions and therefore selection pressures.
- Plasticity can mediate the interaction between immediate adaptation and long-term evolution.
PredPreyGrass provides a system in which both timescales can be studied together.
Research Questions
The study of selected cooperation in PredPreyGrass focuses on:
- Under what ecological conditions does cooperation spread through selection?
- How stable are cooperative traits against invasion by defectors?
- When do cooperative and defective strategies coexist evolutionarily?
- How does population structure affect evolutionary outcomes?
- How does plasticity influence the evolution of cooperation?
Summary
Selected cooperation is:
- a population-level adaptive process,
- driven by differential reproduction and survival,
- capable of stabilizing coordination under the right ecological and social conditions,
- often fragile when exploitative strategies can invade.
Understanding its dynamics is essential for explaining the nature component of cooperation and how it interacts with lifetime learning.
In PredPreyGrass, selected cooperation forms the nature component of a two-timescale theory of cooperation.