For the past few weeks, we’ve been conducting experiments in the Quandary Den, a simple game simulation where the players evolve strategies. We’ve been looking at how complex solutions can evolve from simpler ones. So far, no single technical definition captures everything we mean informally by complexity, but for our purposes here I am describing a solution as more complex if it involves more distinct parts that are each individually essential. Last week we confirmed that there are neutral roads to such complexity, meaning the changes involved in going from a simpler solution to a more complex one do not change fitness and are not selected for. Nevertheless, even though we are not selecting for higher complexity either directly or indirectly, complexity always increases in these experiments. Then I identified a way in which I might have inadvertently made greater complexity more likely, and proposed a modification to our experimental setup that would mitigate that potential bias. Did the road still lead to more complex solutions? What did you find? Let’s look at my results.
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constructive neutral evolution
Science Corner: Traveling on the Level
When we last visited the Quandary Den, we saw how our players could take an adaptive path to complexity. By complexity, I mean that the solution to the challenge of the room involved multiple players making distinct and essential contributions. We saw that they were essential by looking at the last-on-the-bus (LOTB) score which looks at the difference between the team’s result with that player and without. If a player has a LOTB score of zero, then their contributions are not essential; they might score one or more points but when they are not there someone else is capable of scoring them. And I say the path to that complexity was adaptive because the experiment started with random actions and applied positive selection whenever mutations added players or actions that contributed to a solution. Then I asked whether other pathways to complexity were possible and provided a simulation for answering that question.
[Read more…] about Science Corner: Traveling on the Level