University of Birmingham, School of Computer Science.
Artif Life. 2022 Jun 9;28(1):134-153. doi: 10.1162/artl_a_00366.
It is already well known that environmental variation has a big effect on real evolution, and similar effects have been found in evolutionary artificial life simulations. In particular, a lot of research has been carried out on how the various evolutionary outcomes depend on the noise distributions representing the environmental changes, and how important it is for models to use inverse power-law distributions with the right noise colour. However, there are two distinct factors of relevance-the average total magnitude of change per unit time and the distribution of individual change magnitudes-and misleading results may emerge if those factors are not properly separated. This article makes use of an existing agent-based artificial life modeling framework to explore this issue using models previously tried and tested for other purposes. It begins by demonstrating how the total magnitude and distribution effects can easily be confused, and goes on to show how it is possible to untangle the influence of these interacting factors by using correlation-based normalization. It then presents a series of simulation results demonstrating that interesting dependencies on the noise distribution remain after separating those factors, but many effects involving the noise colour of inverse power-law distributions disappear, and very similar results arise across restricted-range white-noise distributions. The average total magnitude of change per unit time is found to have a substantial effect on the simulation outcomes, but the distribution of individual changes has very little effect. A robust counterexample is thereby provided to the idea that it is always important to use accurate environmental change distributions in artificial life models.
众所周知，环境变化对真实进化有很大的影响，在进化人工生命模拟中也发现了类似的影响。特别是，已经进行了大量的研究，研究了各种进化结果如何取决于代表环境变化的噪声分布，以及模型使用具有正确噪声颜色的逆幂律分布的重要性。然而，有两个明显相关的因素——单位时间内变化的平均总幅度和个体变化幅度的分布——如果不适当分离这些因素，可能会得出误导性的结果。本文利用现有的基于代理的人工生命建模框架，使用以前为其他目的尝试和测试过的模型来探讨这个问题。它首先演示了如何容易混淆总幅度和分布效应，然后展示了如何通过基于相关的归一化来解开这些相互作用因素的影响。然后提出了一系列模拟结果，表明在分离这些因素后，对噪声分布的有趣依赖仍然存在，但涉及逆幂律分布噪声颜色的许多影响消失了，在受限范围的白噪声分布中会出现非常相似的结果。结果表明，单位时间内变化的平均总幅度对模拟结果有很大的影响，但个体变化的分布几乎没有影响。因此，为在人工生命模型中总是需要使用准确的环境变化分布的观点提供了一个强有力的反例。
