In a previous article, we introduced a number of visualization techniques that we had developed for monitoring the dynamics of artificial competitive coevolutionary systems. One of these techniques involves evaluating the performance of an individual from the current population in a series of trials against opponents from all previous generations, and visualizing the results as a 2D grid of shaded cells or pixels: qualitative patterns in the shading can indicate different classes of coevolutionary dynamics. As this technique involves pitting a current individual against ancestral opponents , we referred to the visualizations as CIAO plots. Since then, a number of other authors studying the dynamics of competitive coevolutionary systems have used CIAO plots or close derivatives to help illuminate the dynamics of their systems, and it has become something of a de facto standard visualization technique. In this very brief article we summarize the rationale for CIAO plots, explain the method of constructing a CIAO plot, and review important recent results that identify significant limitations of this technique.

An artificial life entertainment-software product called Creatures was released in Europe in late 1996 and in the United States and Japan in mid-1997. When installed on a domestic computer (PC or Macintosh), each Creatures CD-ROM creates a virtual world in which autonomous software agents exist. The agents, known as “norns,” interact with the human user, with each other, and with objects in their virtual world. Each norn coordinates perception and action via its own modular recurrent neural network: Each network has Hebbian learning, plus diffuse modulation of activity via a “hormonal” system that is part of that norn's “biochemistry.” Details of each norn's neural network and biochemistry are genetically specified, and norns can breed via sexual reproduction. In the reproduction process, genetic material may be mutated and may also be subjected to “gene duplications” that enable potentially unlimited increases in complexity of the norns' design. Over 500,000 Creatures CD-ROMS have now been sold. As each installed copy of Creatures can support 5 to 10 simultaneously existing individual norns, it seems reasonable to estimate that there are up to 5 million norns existing in the “cyberspace” provided by the global Creatures user community. Continued growth of the global norn population, to figures measured in tens of millions, is quite likely. Although a commercial product, the Creatures digital ecosystem should be of interest to artificial life scientists: There are obvious parallels with Yaeger's Poly World and Ray's Net Tierra systems. This article provides a detailed discussion of the links between the artificial life literature and the technology used in Creatures and includes anecdotal discussion of the “digital naturalism” witnessed on the many independent websites maintained by Creatures enthusiasts.