Adaptation in the multistable system

Excerpt from chapter 16 of W. R. Ashby, _Design for a Brain_, Wiley, 2nd edn, 1960, pp. 205-14. [[on The W. Ross Ashby Digital Archive](] [[on the Internet Archive](] Snippets of text (from the beginning, maybe the middle, and the end) appear below, to give a sense of the content for the chapter. For more depth, the original source is cited, above. ---

1\.1. Continuing our study of types of environment we next consider, after Figures 15/7/1 and 15/8/1 [not included in this excerpt], the case in which the subsystems of the environment are connected unrestrictedly in direction, so that feedbacks occur between them. This type of environment may vary according to the amounts of communication (variety) that are transmitted between subsystem and subsystem. Two degrees are of special interest as types: * 1\. Those in which it is near the maximum - the richly joined environment. (The exposition is more convenient if we consider this case first, as it can be dismissed briefly.) * 2\. Those in which the amount is small. [p. 230]

## The Richly Joined Environment 1\.2. When a set of subsystems is richly joined, each variable is as much affected by variables in other subsystems as by those in its own. When this occurs, the division of the whole into subsystems ceases to have any natural basis. [p. 230] [....]

## The Poorly Joined Environment 1\.5. We will finally consider the case in which the environment consists of subsystems joined so that they affect one another only weakly, or occasionally, or only through other subsystems. It was suggested in section 15/2 that this is the common case in almost all natural terrestrial environments. [p. 233] [....]

## Summary We are now in a position to summarize the answer, given by the intervening chapters, to the objection, raised in section 11/2, that ultrastability cannot be the mode of adaptation used by living organisms because it would take too long. We can now appreciate that the objection was unwittingly using the assumption that the organism and the environment were richly joined both within themselves and to each other. Evidence has been given, in section 15/2, that the actual richness is by no means high. Then Chapters 15 and 16 have shown that when it is not high, adaptation by ultrastability can occur in a time that is no longer impossibly long. Thus the objection has been answered, at least in outline. [pp. 239-240] There we must leave the matter, for a closer examination would have to depend on measurements of actual brains adapting to actual environments. The study of the matter should not be beyond the powers of the present-day experimenter. [..J [p. 240]