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Plasticity and Strong Reciprocity. Zeke Hindle and Sarah Llanes Evolutionary 452 22 November 2011 http://www.youtube.com/watch?v=gj57rI1_JX8. How Learning Affects the Evolution of Strong Reciprocity. Juan Pablo Calderon and Roberto Zarama
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Plasticity and Strong Reciprocity Zeke Hindle and Sarah Llanes Evolutionary 452 22 November 2011 http://www.youtube.com/watch?v=gj57rI1_JX8
How Learning Affects the Evolution of Strong Reciprocity Juan Pablo Calderon and Roberto Zarama From the Journal of Adaptive Behavior 2006 Volume 14 Pages 211-221
Introduction • Definitions of relevant terms Phenotypic plasticity, lifetime adaptations, ontogenic adaptations, and learning are all used interchangeably and mean “changes that an individual undergoes within his/her lifetime and that will not going to be [sic] inherited directly by offspring” Strong Reciprocity defined as the evolved behavior of humans to “cooperate with non-kin, including people that they will never meet again, and punish non-cooperators even at a personal cost”. Ultimatum Game- Two players (one proposer, one responder) where players split the pot if proposal is sufficient to make the responder accept said offer. Homo Economicusdefined as “a self-interested being who will try to maximize his or her own monetary utility.
Introduction • Previous Literature The model for the following experiment was largely taken from the ultimatum game model used by Sanchez and Cuesta (2005), with a few variations, namely the agents and genetic algorithms altered to allow for the study of the affects of plasticity on the evolution of strong reciprocity within the game itself.
Model • Same model as ultimatum game but nature of participants (agents) and genetic algorithm was altered to allow for plasticity. • Rigid Agents- Genes (specific actions allowed in the course of the game) randomly selected and force said agent to act in a particular way (i.e. not able to change amount proposed or responded to). • Genetic Algorithm- Two agents randomly selected, one with higher fitness (more money) is replicated (offspring) while the other (less relative money) is discarded from the game. • Plastic Agents- Allowed the ability to adapt. Given a certain genome initially but then allowed to adapt by the augmentation of the phenome. Three Types of Plasticity Type 1 Type 2 Type 3 Inherited
Results • Scatterplotswere used to determine the relative changes in the given condition over time. • Rigid Agents- show the rational solution predicted by homo economicus meaning the agents proposed very little and accepted almost anything. Solution is not stable (fluctuates around a mean value). • Plastic Agents Type 1- Overall causes the spread of learnt behaviors and on average decreases offer by 20 percent and increased response by 20 percent. Type 2 and 3- As adaptability of agents increases the average offers and acceptance thresholds increase. As number of games before a given agent becomes rigid increases, offers made are more generous and thresholds less strict. • Plasticity as Evolutionary Stable Strategy (Inherited)
Discussion and Conclusions • Costs of Plasticity • Stochasticitydefined as learned wrong behavior by inadequate examples. • Time wasting cost due to learning process. • Mistakes inherent to given form of learning. • Benefits of Plasticity -Efficient exploitation of given environment by agent. -Happens within lifetime and not over generations or mutations. -Might be evolutionarily stable. -Increases diversity of behaviors and genetic diversity thereby increasing the level of -cooperation amongst group members of population -Reduces selection pressure and retains a less converged population. -Allows genetically similar population to display diverse behaviors. -Over time, changes overall behavior of population from selfish to altruistic.
Critical Review • Pros -The fact that agents have no memory and anonymous to one another reflects the fact that strong reciprocity does not consider others but only the individual. -Aware that learning (plasticity) is not always beneficial and has its drawbacks. -Variety of methods, conditions, and variables allows researchers to see a wide variety of characteristics associated with the affects of plasticity on strong reciprocity. • Cons -Limited amount of generations and simulations lack the realism of the natural world. -Could make more elaborate learning algorithms and characteristics of agents more reflective of reality. -Complexity of models, variables, conditions, diagrams, and charts difficult to explain to the average reader and could be simplified to reach a larger audience.
Test Questions • Multiple Choice 1) Sanchez and Cuesta’s Model of evolutionary game theory (2005) predicts the emergence of strong reciprocity based upon selection acting on: a) the individual b) the group c) both a and b 2) Over time plasticity will evolve behaviors that can be described as: a) selfish b) altruistic c) destructive d) both a and b 3) By definition, strong reciprocity takes into account all of the following except: a) cooperation with kin b) cooperation with non-kin c) cooperation with people that will never interact again d) cooperation even at personal cost
Test Questions • True/ False 1) Plasticity can be defined as changes that an individual undergoes within his/her lifetime that will be directly inherited by the offspring of said individual. T or F 2) Altruistic punishment is positively correlated with the evolution of plasticity and strong reciprocity. T or F 3) The evolutionary costs of plasticity are higher than the benefits of plasticity that’s why were are all selfish and mean people. T or F
THE END!!!!!!!!!!!! Any Questions?!?!?!?