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Reviews of Relevant Books
'Emergence': a relatively new and popular term to describe complexity resulting from bottom-up or self- organization used in many fields, from the natural sciences to computer science to economics. However, recognition of such emergent phenomena pre-dates the term itself and has as its contributors many influential thinkers, themselves from a variety of fields, such as Turing, Darwin, and Engels. In Emergence: The connected lives of Ants, Brains, Cities, and Software author and web technologist Steven Johnson explores the work of thinkers like these, as well as many other current models of emergence in the field of biology, sociology, and technology. His emphasis is on the role of locally interacting agents which yield bottom-up forces that produce global behavior as well as other emergent properties.
The book begins with a model that has played a leading role in understanding and elucidating many characteristics of complex systems: ant colonies. Although an ant colony requires a queen for perpetuating the population, her role stops there. The queen, despite implications of the title, plays no role in orchestrating the behavior of the colony. Instead the activities of the colony result from interactions between individual ants. Each ant lives by a simple set of rules that guide her behavior. For instance, an ant's decision to forage is dependent on the frequency of contact she has with other ants in her immediate surroundings, rather than any knowledge of what the colony as a whole is doing. The result is what an onlooker might observe as intentional behavior or hierarchical organization. Many behaviors of the colony though, such as allocation of duties or strategic placement of midden and ant corpses, result from this kind of collective behavior or "swarm intelligence". Attempts to identify any such true queen, directing ant, or "pacemaker" element prove fruitless.
Johnson connects these ideas of emergent organization to city development. Urban organization too exhibits patterns formed by lower-level interactions. While top-down forces (zoning laws, planning commissions, etc.) are without question present, there also exist bottom-up forces that together are responsible for certain patterns. Interactions between individuals shape and define communities, form segregated populations, and so on. Local forces between businesses, like competition for customers, help shape commercial distribution. Johnson cites Jane Jacobs, a writer on urban planning, who emphasizes the importance of "sidewalk culture." This alludes to the belief that certain pre-planned organizations are destined to fail due to lack of lower-level interactions by individuals needed for the layout to survive and flourish. This rests not literally on sidewalks themselves, but on the idea that sidewalks serve as a venue for interaction between individuals and then among communities. Interaction, in turn, has the potential to modify subsequent behavior and interactions as Jacobs stresses, "Encountering diversity does nothing for the global system of the city unless that encounter has a chance of altering your behavior." (96)
Johnson goes on to describe other instances of bottom-up organization in the biology of morphogenesis and the brain, in areas of computer science including learning, artificial intelligence, and genetic algorithms, as well as in the current technological world, including the Web, computer software, gaming, and even the media. Through these various discussions he hits on the most salient features of emergent organization and behavior, the foremost characteristic being that of locality.
The fact that agents-- whether they be ants, neurons, human individuals, or agents of another sort-- base their behavior on their local environments without requiring knowledge about the system as a whole is perhaps the foremost reason why emergent complexity is so interesting. The "organizing force" is then a decentralized one with no single agent being in charge. Again, an ants only source of information comes from those it comes into contact with, and she can only retain that memory for a short period of time (eliminating the possibility of surveying every single ant before deciding on a behavior). Likewise, a city business may settle based on other businesses within, say, a half mile radius while paying no heed to similar businesses that are located tens of miles away. Johnson points to the example of morphogenesis in the context of embryonic development to further emphasize the role of locality: how does a (precursor) cell specialize? At first glance, it may seem like DNA is orchestrating overall development. No doubt DNA is influential in development, but every cell contains the same DNA. The question becomes, how does a cell know which part of the very large code to follow? The answer, not surprisingly, lies in surrounding cells and (semiochemical) signals that they elicit. This illustrates further that agents within emergent systems not only "think" locally-- that is, base their behavior on the local environment-- but they also act locally as well. An embryonic cell, once specialized may send out messages to its neighbors to influence their development, much like it was once influenced, but the receiving cells are only those nearby rather than the entire group of cells.
If one looks hard enough, emergent phenomena are to be found in many places: the unique patterns of snowflakes, the alternating stripes of zebras, or sand dunes of the desert. But the truly remarkable instances of emergent phenomena are those systems that are adaptive, and monitoring a system over time can lead to interesting observations. Johnson appropriately raises another intriguing aspect of emergent systems-- their evolution and ability to "learn". Tracking an ant colony over time shows that its behavior, measured by activity and interaction with neighboring colonies, changes as it grows in size and in time. The older a colony, for example, the more likely it is to avoid confrontation with another colony by foraging along new routes. The striking thing is that an ant's lifespan is at longest twelve months, while a colony can exist for over a decade. Therefore, there is nothing inherent in the ant that determines the colony behavior; each ant, no matter when it exists in the lifespan of a colony, follows the same rules. The colony behavior emerges as a function of its evolution over time. "The persistence of the whole over time-- the global behavior that outlasts any of its component parts-- is one of the defining characteristics of complex systems," Johnson states. (82) These types of adaptations by emergent systems provide new ways of thinking about learning. Learning is frequently thought of as something done by a self-aware organism. But Johnson stresses, "...learning is not just about being aware of information; it's also about storing information... respond[ing] to changing patterns." (103) A system might react to some sort of change-- a change in local behavior, or number of agents-- and then exhibit a new type of global behavior. If this new type of global behavior allows the system to continue to exist with time, the change can be viewed as adaptive. "Learning" boils down to adaptation, and storing information is simply the perpetuation and stability of a group. Akin to the case of locality, changes in behavior by agents are directed towards the short-term, not long term. Johnson refers to this consequence as a "latent purpose". For example, the aim of an individual setting up a business in a particular location is for financial success during the span of an individual lifetime, he or she is ignorant of or unconcerned with any long-term organization of the city over the span of many lifetimes.
Johnson goes on to explore the existence of bottom-up forces in the technological world. He cites coverage by the media and national news as operating on a positive feedback mechanism determined in a bottom-up fashion from local stations. On the other hand, on-line programs may operate based on negative types of feedback. Sites that recommend new products, like Amazon.com, adapt over time to an individual's taste based on user input. The gaming community alone boasts many instances of bottom-up, emergent forces. Many games today involve not a specified aim or objective, but rather an exploration of possibilities by the player. SimCity, for example, very closely parallels real urban development. The user has only indirect control of what happens in a city, the rest being determined by lower-level parameters in the game. Johnson also explores many issues about the Web. Does it self-organize? Not quite yet, according to Johnson. Although it is similar to many emergent systems in that it involves a large number of connections, it lacks the property of bi-directionality. That is, the input is largely in one direction-- linking of web pages without mutual linking. However, many smaller web communities are self organizing by allowing users to explore particular sites and then provide a personal rating, something that eventually affects the likelihood someone else will come across the same page or community.
Although Johnson stresses some of the practical applications of emergent systems, some of the broader implications of emergence he touches on cannot be ignored. For one, knowledge and science itself are easily thought of through the lens of emergence. Individual interaction and engagement act as the lower level agents which give rise to the collective property of knowledge. Knowledge is preserved or "stored" through existence of a group of humans. In his discussion of cities, Johnson notes the advancement of ideas due to the existence of urban life, or rather, groups of humans in close contact.
For the reader interested in biological implications of emergence, Johnson highlights different ways of thinking about more abstract ideas. Personality, for example, can be thought of as the collective sum of a number of biofeedback mechanisms, mechanisms controlling things not thought of as being directly related to personality, such as adrenaline. But more interesting is Johnson's discussion of human consciousness. Though "the jury is still out" on the subject, a reasonable model for consciousness and much of human intelligence is as an emergent entity somehow brought into existence by locally interacting simpler elements-- neurons. One step up from self-awareness may be awareness of others, as in the case of humans and primates. Johnson suggests that thinking of self-awareness as preceding awareness of other individuals may be backwards. By first recognizing and forming expectations of others, individuals then become aware of their own existence. Of course, the third alternative exists as well. Self-awareness and awareness of others may simultaneously emerge at some certain point or "threshold", akin to a phase transition which transforms a simple system into an emergent one.
Johnson's survey of a wide range of models reveal that emergent organization appears in many contexts, both natural and man-made (though, this begs the question of how much influence we can directly exert on social phenomena/organization despite what we may think). Emergence phenomena show that decentralized and distributed forces are in fact a very real and powerful force. Although many ideas like theories of the mind remain (momentarily) philosophical in nature, such imagined models of emergence promote new ways of exploring emergent systems and raise new questions-- how might an emergent system form expectations or match its state with others, and so on. As Johnson encourages, emergence provides us with tools to implement in our daily lives as well as new routes for science to explore.
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