9.4
	Author: Steve Johnson Excerpt: Why do people cluster together in neighbourhoods? How do Internet communities spring up from nowhere? Why is a conscious even though no single neuron is?...The answer, as Steven Johnson's groundbreaking book shows, is emergence: change that occurs from the bottom up. .: Buy at Amazon.com :. .: Buy at Amazon.co.uk :.

Very rarely does a book excite me as much as Steven Johnson's Emergence did. It was an immensely compelling read, covered a vast range of topics and was nothing short of inspiring.

The initial chapter looks at ants, slime mold cells and other more natural instances of emergent systems. I always knew ant colonies were very interesting instances of emergent behaviour, but had never read much about them beyond the AI/ALife material I've seen. Emergence brings up some incredibly interesting facts: ants often setup their waste dumps and 'cemeteries' at points that are geometrically equivalent to the furthest points from both the nest entrance and each other. Not only that, ants switch jobs automatically (perhaps from food gathering to waste duty) - the ant colony therefore always runs at an optimal efficiency despite the lack of a central authority (the queen ant is a bad name, since she does nothing to rule over the ants). What I found most fascinating though, was that ant colonies as a whole actually mature! For example, "adolescent" ant colonies (4-8 years old) are much more aggressive, whereas older ant colonies (perhaps 10-15 years old) are a lot more reserved - but an ant only survives one year, only the queen ant lives the duration of the colony itself. So despite the entire population rotating every year, the colony as a whole matures and develops!

The book goes into some depth about slime mold cells and a StarLogo simulation of them, which subsequently inspired me to write my own Java simulation (pictures below).

Subsequent chapters deal with ideas such as urban planning (as well as the inevitable parallel of the SimCity world). The book discusses how Manchester was formed in such a seemingly random way, yet out of the chaos, districts were formed along with their own accompanying micro-communities. Media frenzies (such as the Clinton scandals), Slashdot, eBay, Sims Online and the WWW in general are also discussed in a truly stimulating fashion. As a regular on both Slashdot and eBay, it was interesting to read about websites I frequent as emergent societies!

In short, it is very hard to write about this book in any concise form. It covers a tough subject, emergence is inherently not for the faint-hearted, but Johnson approaches it in a novel fashion. All the chapters are tied together, and while no mathematics, equations or theories are covered, it provides the reader was a great overview of emergence. As far as artificial intelligence goes, there is little material for the die-hard AI enthusiast to mull over. Artificial Life is touched on a lot, as well as other fringe sciences like chaos. My view (as well as many others') is that intelligence itself is emergent, so this book gave me a lot to think about when applying some of the principles discussed to AI.

A must-read for AI/ALife/popular science aficionados alike!