Social Behaviors and Game Theory

Introduction to Social Behaviors

• The lecture focuses on two aspects of social behavior: cooperation and conflict.

• This lecture covers cooperative behavior and altruism, while the next one will discuss negative behaviors related to conflict.

• Cooperative behaviors are actions that can benefit two or more individuals in a social group.

Key Concepts of Cooperative Behavior

• Alarm Calling Behavior:

  • Example: Squirrels engage in alarm calls to warn others of predators, such as hawks or foxes.

  • Highlights species like meerkats where individuals take turns looking out for threats, which may involve risking their safety for the benefit of the group.

• Evolutionary Puzzle:

  • Researchers ask: Why would an individual risk itself to benefit others? This question drives studies in behavioral ecology to understand the mechanisms behind these actions.

• Cooperative Breeding:

  • Notably seen in birds such as scrub jays, where individuals help raise the young of other nesters instead of breeding themselves.

  • Example: In scrub jay populations, younger birds will often assist their parents in feeding and protecting their siblings, thus increasing the survival rate of the chicks.

  • Researchers question why these helpers would sacrifice their own reproduction for the benefit of the offspring of others, linking this behavior to inclusive fitness.

• Eusociality:

  • Defining characteristics include overlapping generations, cooperative breeding, and a progressive division of labor in tasks.

  • Example: In a naked mole rat colony, only one queen breeds, while other females may become queens if the current one dies. The division of labor is clear, with castes of workers performing different roles such as foraging and defense, exemplified by species like leafcutter ants, where workers gather leaves and take them back to the colony to cultivate fungus for food.

Definitions of Social Behavior

• Social Behavior:

  • Interactions among individuals of the same species that can affect the fitness of those individuals. Examples include competition for mates, cooperative hunting, or mutual grooming among primates.

• Cooperation:

  • A behavior that benefits both individuals involved, potentially seen in mutual grooming among primates. For instance, vervet monkeys engage in grooming to strengthen social bonds and reduce tension within the group.

• Altruism:

  • Behavior that increases another individual’s fitness at the cost of the individual performing the behavior, observed in various species through acts like food sharing and warning calls.

  • Example: In African elephants, older females often protect younger family members from predators, risking their own safety for the well-being of the group.

  • This concept posed a challenge to Darwin's theory of natural selection, presenting a seeming paradox in the survival of the fittest.

Understanding Evolution of Cooperative Behaviors

• Gene Fitness Over Individual Fitness:

  • Evolutionary biology must consider gene fitness rather than just individual fitness, highlighting the importance of genetic similarities among groups that promote cooperative traits.

First Explanation for Cooperative Behaviors: Immediate Benefits

• These behaviors can generate shared benefits for those who participate, securing their collective survival.

  • Example: Two female lions defending their young against a threatening male involves collaborative defense, lowering individual risk and improving the chance of all offspring's survival.

  • Another example can be found in pack-hunting canids, such as wolves, where a coordinated hunting strategy increases the success rate of capturing prey, ensuring food for the entire group.

Second Explanation: Game Theory

• Game theory provides a framework for analyzing interactions and evolving strategies using payoff matrices.

• Hawk-Dove Game:

  • Analyzes strategies in fights over resources, where players choose between aggressive (hawk) or peaceful (dove) strategies.

  • Example: In territorial disputes, male songbirds may resort to aggressive displays (hawk strategy) when challenged, while avoiding direct confrontation (dove strategy) in situations where they assess their opponent is stronger.

• Payoff Matrix:

  • Multiple factors including costs and rewards influence the strategies adopted by individuals involved in conflicts, illustrating the complexity of decision-making in social behaviors.

Third Explanation: Reciprocity

• Reciprocity is observed when repeated encounters lead to mutual benefits:

  • It underscores how relationship dynamics can shift toward cooperation through ongoing social interactions.

  • Example: Vampire bats engage in reciprocal blood sharing, where bats that fail to find food are fed by those they previously helped, enabling survival through mutual altruism.

• Iterated Prisoner's Dilemma:

  • Provides a real-world analogue for social dilemmas in repeated games.

• Strategy named Tit for Tat:

  • Involves cooperation on the first move, followed by matching the partner's previous action, which promotes a stable cooperation model when endgame scenarios incentivize collaboration.

Kin Selection and Inclusive Fitness

• Altruism can be explained through kin selection, which suggests that behaviors that help relatives, thus promoting the survival of shared genes, can be evolutionarily advantageous.

• Darwin's reflection illustrates that selection can act on families and extended relations to explain altruistic behaviors more robustly.

• Hamilton's Rule:

  • This theory proposes that altruism is favored when: \text{Benefit} \times \text{Relatedness} > \text{Cost}

  • Example of Kin Selection in Nesting Birds:

  • Long-tailed tits preferentially help their close relatives in raising young; such kin discrimination ensures that altruistic behaviors bolster the survival and future reproduction of genetic relatives.

Dicyostelium and Kin Discrimination

• An example from slime molds illustrates altruistic behavior where individual Dicyostelium cells sacrifice themselves to form fruiting bodies, promoting the survival of other cells.

• Experiments indicate that Dicyostelium preferentially forms aggregates with genetically similar individuals, reinforcing the kin selection theory through observable behaviors.

Conclusion

• The core idea in understanding social behaviors focuses on gene frequencies in populations and their evolution.

• Instead of singularly emphasizing individual success, appreciating gene survival and propagation mechanisms—especially through altruistic behaviors—offers a comprehensive perspective on evolution.