Interactions between Learning and Evolution: The Outstanding Strategy Generated by the Baldwin E ect

The Baldwin e ect is known as interactions between learning and evolution, which suggests that individual lifetime learning can in uence the course of evolution without the Lamarckian mechanism. Our concern is to consider the Baldwin e ect in dynamic environments, especially when there is no explicit optimal solution through generations and it depends only on interactions among agents. We adopted the iterated Prisoner's Dilemma as a dynamic environment, introduced phenotypic plasticity into strategies, and conducted the computational experiments, in which phenotypic plasticity is allowed to evolve. The Baldwin e ect was observed in the experiments as follows: First, strategies with enough plasticity spread, which caused a shift from defective population to cooperative population. Second, these strategies were replaced by a strategy with a modest amount of plasticity generated by interactions between learning and evolution. By making three kinds of analysis, we have shown that this strategy provides the outstanding performance. Further experiments towards open-ended evolution have also been conducted so as to generalize our results.