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Emergence: The Connected Lives of Ants, Brains, Cities, and Software
 
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Emergence: The Connected Lives of Ants, Brains, Cities, and Software [Format Kindle]

Steven Johnson

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Amazon.com's Best of 2001

An individual ant, like an individual neuron, is just about as dumb as can be. Connect enough of them together properly, though, and you get spontaneous intelligence. Web pundit Steven Johnson explains what we know about this phenomenon with a rare lucidity in Emergence: The Connected Lives of Ants, Brains, Cities, and Software. Starting with the weird behavior of the semi-colonial organisms we call slime molds, Johnson details the development of increasingly complex and familiar behavior among simple components: cells, insects, and software developers all find their place in greater schemes.

Most game players, alas, live on something close to day-trader time, at least when they're in the middle of a game--thinking more about their next move than their next meal, and usually blissfully oblivious to the ten- or twenty-year trajectory of software development. No one wants to play with a toy that's going to be fun after a few decades of tinkering--the toys have to be engaging now, or kids will find other toys.

Johnson has a knack for explaining complicated and counterintuitive ideas cleverly without stealing the scene. Though we're far from fully understanding how complex behavior manifests from simple units and rules, our awareness that such emergence is possible is guiding research across disciplines. Readers unfamiliar with the sciences of complexity will find Emergence an excellent starting point, while those who were chaotic before it was cool will appreciate its updates and wider scope. --Rob Lightner

Extrait

Introduction: Here Comes Everybody!

In August of 2000, a Japanese scientist named Toshiyuki Nakagaki announced that he had trained an amoebalike organism called slime mold to find the shortest route through a maze. Nakagaki had placed the mold in a small maze comprising four possible routes and planted pieces of food at two of the exits. Despite its being an incredibly primitive organism (a close relative of ordinary fungi) with no centralized brain whatsoever, the slime mold managed to plot the most efficient route to the food, stretching its body through the maze so that it connected directly to the two food sources. Without any apparent cognitive resources, the slime mold had "solved" the maze puzzle.

For such a simple organism, the slime mold has an impressive intellectual pedigree. Nakagaki's announcement was only the latest in a long chain of investigations into the subtleties of slime mold behavior. For scientists trying to understand systems that use relatively simple components to build higher-level intelligence, the slime mold may someday be seen as the equivalent of the finches and tortoises that Darwin observed on the Galápagos Islands.

How did such a lowly organism come to play such an important scientific role? That story begins in the late sixties in New York City, with a scientist named Evelyn Fox Keller. A Harvard Ph.D. in physics, Keller had written her dissertation on molecular biology, and she had spent some time exploring the nascent field of "nonequilibrium thermodynamics," which in later years would come to be associated with complexity theory. By 1968, she was working as an associate at Sloan-Kettering in Manhattan, thinking about the application of mathematics to biological problems. Mathematics had played such a tremendous role in expanding our understanding of physics, Keller thought -- so perhaps it might also be useful for understanding living systems.

In the spring of 1968, Keller met a visiting scholar named Lee Segel, an applied mathematician who shared her interests. It was Segel who first introduced her to the bizarre conduct of the slime mold, and together they began a series of investigations that would help transform not just our understanding of biological development but also the disparate worlds of brain science, software design, and urban studies.

If you're reading these words during the summer in a suburban or rural part of the world, chances are somewhere near you a slime mold is growing. Walk through a normally cool, damp section of a forest on a dry and sunny day, or sift through the bark mulch that lies on a garden floor, and you may find a grotesque substance coating a few inches of rotting wood. On first inspection, the reddish orange mass suggests that the neighbor's dog has eaten something disagreeable, but if you observe the slime mold over several days -- or, even better, capture it with time-lapse photography -- you'll discover that it moves, ever so slowly, across the soil. If the weather conditions grow wetter and cooler, you may return to the same spot and find the creature has disappeared altogether. Has it wandered off to some other part of the forest? Or somehow vanished into thin air, like a puddle of water evaporating?

As it turns out, the slime mold (Dictyostelium discoideum) has done something far more mysterious, a trick of biology that had confounded scientists for centuries, before Keller and Segel began their collaboration. The slime mold behavior was so odd, in fact, that understanding it required thinking outside the boundaries of traditional disciplines -- which may be why it took a molecular biologist with a physics Ph.D.'s instincts to unravel the slime mold's mystery. For that is no disappearing act on the garden floor. The slime mold spends much of its life as thousands of distinct single-celled units, each moving separately from its other comrades. Under the right conditions, those myriad cells will coalesce again into a single, larger organism, which then begins its leisurely crawl across the garden floor, consuming rotting leaves and wood as it moves about. When the environment is less hospitable, the slime mold acts as a single organism; when the weather turns cooler and the mold enjoys a large food supply, "it" becomes a "they." The slime mold oscillates between being a single creature and a swarm.

While slime mold cells are relatively simple, they have attracted a disproportionate amount of attention from a number of different disciplines -- embryology, mathematics, computer science -- because they display such an intriguing example of coordinated group behavior. Anyone who has ever contemplated the great mystery of human physiology -- how do all my cells manage to work so well together? -- will find something resonant in the slime mold's swarm. If we could only figure out how the Dictyostelium pull it off, maybe we would gain some insight on our own baffling togetherness.

"I was at Sloan-Kettering in the biomath department -- and it was a very small department," Keller says today, laughing. While the field of mathematical biology was relatively new in the late sixties, it had a fascinating, if enigmatic, precedent in a then-little-known essay written by Alan Turing, the brilliant English code-breaker from World War II who also helped invent the digital computer. One of Turing's last published papers, before his death in 1954, had studied the riddle of "morphogenesis" -- the capacity of all life-forms to develop ever more baroque bodies out of impossibly simple beginnings. Turing's paper had focused more on the recurring numerical patterns of flowers, but it demonstrated using mathematical tools how a complex organism could assemble itself without any master planner calling the shots.

"I was thinking about slime mold aggregation as a model for thinking about development, and I came across Turing's paper," Keller says now, from her office at MIT. "And I thought: Bingo!"

For some time, researchers had understood that slime cells emitted a common substance called acrasin (also known as cyclic AMP), which was somehow involved in the aggregation process. But until Keller began her investigations, the conventional belief had been that slime mold swarms formed at the command of "pacemaker" cells that ordered the other cells to begin aggregating. In 1962, Harvard's B. M. Shafer showed how the pacemakers could use cyclic AMP as a signal of sorts to rally the troops; the slime mold generals would release the compounds at the appropriate moments, triggering waves of cyclic AMP that washed through the entire community, as each isolated cell relayed the signal to its neighbors. Slime mold aggregation, in effect, was a giant game of Telephone -- but only a few elite cells placed the original call.

It seemed like a perfectly reasonable explanation. We're naturally predisposed to think in terms of pacemakers, whether we're talking about fungi, political systems, or our own bodies. Our actions seem governed for the most part by the pacemaker cells in our brains, and for millennia we've built elaborate pacemakers cells into our social organizations, whether they come in the form of kings, dictators, or city councilmen. Much of the world around us can be explained in terms of command systems and hierarchies -- why should it be any different for the slime molds?

But Shafer's theory had one small problem: no one could find the pacemakers. While all observers agreed that waves of cyclic AMP did indeed flow through the slime mold community before aggregation, all the cells in the community were effectively interchangeable. None of them possessed any distinguishing characteristics that might elevate them to pacemaker status. Shafer's theory had presumed the existence of a cellular monarchy commanding the masses, but as it turned out, all slime mold cells were created equal.

For the twenty years that followed the publication of Shafer's original essay, mycologists assumed that the missing pacemaker cells were a sign of insufficient data, or poorly designed experiments: The generals were there somewhere in the mix, the scholars assumed -- they just didn't know what their uniforms looked like yet. But Keller and Segel took another, more radical approach. Turing's work on morphogenesis had sketched out a mathematical model wherein simple agents following simple rules could generate amazingly complex structures; perhaps the aggregations of slime mold cells were a real-world example of that behavior. Turing had focused primarily on the interactions between cells in a single organism, but it was perfectly reasonable to assume that the math would work for aggregations of free-floating cells. And so Keller started to think: What if Shafer had it wrong all along? What if the community of slime mold cells were organizing themselves? What if there were no pacemakers?

Keller and Segel's hunch paid off dramatically. While they lacked the advanced visualization tools of today's computers, the two scratched out a series of equations using pen and paper, equations that demonstrated how slime cells could trigger aggregation without following a leader, simply by altering the amount of cyclic AMP they released individually, then following trails of the pheromone that they encountered as they wandered through their environment. If the slime cells pumped out enough cyclic AMP, clusters of cells would start to form. Cells would begin following trails created by other cells, creating a positive feedback loop that encouraged more cells to join the cluster. If each solo cell was simply releasing cyclic AMP based on its own local assessment of the general conditions, Keller and Segel argued in a paper published in 1969, then the larger slime mold community might well be able to aggregate based on global changes in the environment -- all without a pacemaker cell calling the shots.

"The response was very interesting," Keller says now. "For anyone who understood applied mathematics, or had any experience in fluid dynamics, this was old hat to them. But to biologists, it didn't make any sens...

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Amazon.com: 3.6 étoiles sur 5  111 commentaires
155 internautes sur 171 ont trouvé ce commentaire utile 
3.0 étoiles sur 5 Reads like a magazine article 14 avril 2002
Par Dennis Muzza - Publié sur Amazon.com
Format:Relié|Achat vérifié
This book attempts to explain artificial intelligence in terms of how ant colonies, cities, and modern software operate. If it seems to have the feel of a magazine article, it's because it's not written by a professional in the field but by a professional writer who is a frequent contributor to trendy, popular publications such as Feed and Wired. Although it did not give me the understanding I was looking for about emergence theory, I would not dismiss it completely because it does have a lot of interesting information, as any good magazine article would. It has an overview of Jane Jacobs new urbanism that is both complete and illustrating, it explains how an intelligent kind of feedback makes some web sites successful as virtual communities, and what I found most interesting, how video games are evolving in ways that seem to give them a life of their own. If you are looking for an insightful, deep look at artificial intelligence for the layman, Douglas Hofstadter's "Godel Escher Bach" is still unchallenged. On the other hand if you are looking for a more relaxed, amusing and down to earth approach, filled with cool stuff you can impress your friends with, this book is for you.
34 internautes sur 35 ont trouvé ce commentaire utile 
5.0 étoiles sur 5 Intelligence (and more) from Unenlighted Little Parts 20 novembre 2001
Par R. Hardy - Publié sur Amazon.com
Format:Relié
If you see an ant, you pay it little attention. It's the lines of ants that are really fascinating, and the colonies that really get things done. An ant by itself is not only a speck, it is a humble one, capable of little. It isn't just a matter of getting a lot of ants together so that by sheer numbers they multiply what one ant can do. Ants organize. They communicate. They have tasks, they assign workers, they shift assignments as old jobs get done and new ones come up. We have tried to understand this sort of organization in our own way. To get such things done ourselves, we would have to have a leader and subleaders, and in trying to understand ants, we even attributed to the queen of the ant colony a sort of CEO status. She isn't, of course; she is an egg-laying machine, but she is deep in the darkest parts of the colony, and has no idea about what her workers are doing or how to respond to quality assurance suggestions. She is not the chief of the bureaucracy of the ant colony. Something else is. Who is giving the orders?
No one. The ants are self-organizing, according to Steven Johnson, whose bright book _Emergence: The Connected Lives of Ants, Brains, Cities, and Software_ (Scribner) is obviously not just about ants. Ants are just an easy example. Johnson's book is full of satisfying analogies. Take your brain, for instance. Those neurons don't know anything. Each one is capably of firing when stimulated, and that's about it. "No individual neuron is sentient," Johnson writes, "and yet somehow the union of billions of neurons creates self-awareness." Adam Smith posited an "invisible hand" which set the prices in economic systems, some supply and demand force that was completely free of any sort of conscious human control (just as the slime cells didn't have a higher authority). It wasn't planned, it just happened because of the number of independent actors on the economic stage. The immune system possessed by each of us gets smarter over the years as its biochemical parts share information, and it responds with individualized defenses, but it isn't conscious and it has no memory. The host and hostess of that last party you went to didn't decree that everyone would gather in the kitchen, but it happened anyway. Though cities may have a government, no one has told them to set up offices in the center, and branch off into suburbs and malls around them, and no one designed individual neighborhoods to be havens for artists or for homosexuals. The silicon circuits in a handheld computer can't do much but flop on and off, but they can learn your handwriting with remarkable skill. Other electronic stupids at Amazon.com can tell from what you have ordered what might appeal to you in the future, and offer up "your" selections with much more skill than an ad designed for everyone could possibly do.
Emergence is being used in video games, and undoubtedly will be a larger part of the software we interact with every day. There have, up to now, only been primitive and clumsy attempts to allow web sites and browsing to feed back on themselves in some emergent fashion to give users quicker access to just the site they had been long looking for. Couch potatoes, too, would make great ants, since there are so many of them and they could be simply connected with minimal feedback systems, with emergent miniseries and music videos as a result. When Johnson enters the ring as a prophet, one can only allow that his schemes might come to pass and we will have to wait and see. But in explaining a natural system (followed by a technological one) which has been present since before our neurons organized themselves but which has been appreciated by that organization only in the last few decades, Johnson displays enthusiasm and didactic skill. Some are hailing his book as a milestone on the path to the future, and maybe it is, but perhaps more important, it is an exhilarating and instructive course in a current trend of thought.
568 internautes sur 671 ont trouvé ce commentaire utile 
2.0 étoiles sur 5 How not to learn about emergence 14 septembre 2002
Par Edward A. Fagen - Publié sur Amazon.com
Format:Relié
Steven Johnson's "Emergence: The Connected Lives of Ants, Brains, Cities, and Software" (Scribner, New York, 2001),is a very bad book, shallow, careless, and disappointing. I was lured by its nominal subject, which interests me greatly, and now I'm sorry I bought it. Mr. Johnson is a young- very young- video gamer who has managed to parlay a superficial aquaintance with the vocabulary of modern science into a series of trendy popular books, incomprehensibly praised by such authorities as Steven Pinker and Esther Dyson.
The book opens with a fraudulent pictorial simile, juxtaposing a side view of the human brain and a map of Hamburg ca. 1850. Indeed they do resemble each other, and the reader is supposed to infer (with no help from Johnson) that the resemblance arises from the operation of similar governing principles. Quite apart from the validity of this conclusion, it apparently does not trouble Johnson that the brain is three-dimensional and the city map is essentially two-dimensional, or that the comparison would fail if a frontal view of the brain had been chosen, or if Paris or El Paso or Denver had been chosen instead of Hamburg.
It gets worse. At the most fundamental level, after reading the book I find it impossible to say what the author means by "emergence", his nominal title. When he discusses ant colonies it appears to mean swarm intelligence; when he discusses video games it appears to mean interactive software; at still other places it appears to mean whatever recent developments in the realm of computers or biophysics or city planning that he approves of.
Moreover, he appears to be totally ignorant of all science and mathematics that preceded his own adolescence. Although he has a great deal to say about self-organizing systems, you will search the index in vain for the names of John Conway, Oskar Morgenstern, John von Neumann, Stanislaw Ulam, Stephen Wolfram, or most of the other pioneers of the field. When he does recognize a figure from antiquity (i.e., pre-1970), it is with worshipful adulation. He italicizes the name of Marvin Minsky as if he were a demigod, and finds a book by Norbert Wiener "curiously brilliant". What exactly is the curiosity?- that a brilliant mathematician should write a brilliant book? Likewise, you will find no entry in the index under "Boolean networks" or "cellular automata" or "crystallization" or "ferromagnetism." Under "entropy" you will find only the ludicrous assertion that in nonequilibrium thermodynamics "the laws of entropy are temporarily overcome." In short, Mr. Johnson gives new meaning to the phrase "born yesterday," a degree of ignorance and juvenile solipsism that borders on arrogance.
I note that other reader-reviewers assert that the book will provide lay persons with an introduction to a new science. No, it won't. The only thing it will provide is an introduction to bad science.
47 internautes sur 53 ont trouvé ce commentaire utile 
2.0 étoiles sur 5 Mediocre At Best 30 janvier 2002
Par R. Bryant - Publié sur Amazon.com
Format:Relié
Johnson has a riveting introduction and opening but the rest of the book falls flat with a superficial treatment of emergence. The author would also have the reader think that he knows alot about cities and their development, but his actual understanding of the subject is very, very thin.
Try "Signs of Life" by Richard Sole and Brian Goodwin for a much better elucidation of complexity science and the role of emergence. Another book just out is "Self Organization in Biological Systems" published by Princten University Press as part of its series on complexity science.
34 internautes sur 38 ont trouvé ce commentaire utile 
4.0 étoiles sur 5 A good introduction - and more 17 janvier 2002
Par alan - Publié sur Amazon.com
Format:Relié
I wasn't sure, when I bought this book, how much I would get out of it. The reviews I had read painted it as an introductory work and, since I already know a bit about emergence in the context of ecosystems, economies, social insects and human brains, I wondered if it might be too basic.
What can I say? Having read it, I agree that it is an excellent introduction to the subject: clear, wide-ranging and readable. But it is also far more. Even if you know much more than the author about, lets say, ant nests, the quality of the writing and the constant excursions into other fields to draw illuminating comparisons will keep you reading sections you might otherwise want to skip.
Even the book's style says something about the new sciences of complexity: instead of a linear trail of argument from axiom to conclusion, Johnson's thesis grows by picking out repeated patterns from seemingly unrelated fields, adding resolution like a Mandelbrot set slowly emerging from what at first looks like a random scatter of dots. In one chapter an unpromising section on the pitfalls of discussion groups suddenly backlinks to a previous discussion about city growth, gives a quick blast of Adam Smith, segues into media feeding-frenzies and reprises the theme of feedback mechanisms. By the end I was avidly reading about how some bunch called slashdot.org had dealt with the exponential growth of their Star Wars, programming and related geek stuff discussion group, not a topic that would normally grab me.
Unfortunately, the book does flag in a big way in the last few chapters, unless you're seriously interested in video gaming and the future of passive entertainment. In the author's defence, it must be very hard to write about the future of emergence, since its essence is that you never know what will pop up til your system plays out.
To sum up, Johnson is an engaging, insightful writer. He is particularly strong on the interaction between emergence and selection, realising that emergence in itself is not necessarily adaptive or good. He is sometimes a little weak on the difference between bottom-up organisation and true emergence. Finally, look out for the comparison between scientific revolutions and slime moulds: easily the cutest piece of science writing I have seen lately.
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