Emergent Patterns
"They are bottom-up systems, not top-down. They get their smarts from below"
-- Steven Johnson , Emergence

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You are viewing a draft of the book entitled "Patterns – The Art, Soul, and Science of Beholding Nature". The final version of this book has now being published as an Amazon Kindle eBook.

There are some significant changes in the eBook that are not in this draft. You may purchase the eBook here

Some of the ideas in the eBook are contained in posts at my Patterns In Nature Blog. You are encouraged to visit this blog site. If you press the "Like" button shown below, your Facebook page will provide you with short notifications and summaries of new blog posts as they become available.

Emergent behavior is the global (systematic) consequence of local interactions of individuals in the system's population. A pattern in nature is an emergent property because it is the result of a systematic interaction of its component parts. Super-organisms such as bee hives, bird flocks, and coral reefs are complex systems that exhibit unique natural and dynamic patterns that behave in unexpected ways that are not predictable from the behavior of their members. These systems operate as if they have organized themselves. But, in fact, this "self-organization" is an emergent behavior caused by the actions of all individuals within the system acting upon a fixed set of rules. There are no leaders.

Computer scientists call these rule sets algorithms. An algorithm is a list of the exact steps necessary to carry out a desired computation, a list that comes with a guarantee that that the computation will stop with the correct answer. The interesting thing about algorithms is that they require less information and space to operate than does an equivalent table that lists all the possible outcomes of a computation. This compacting of information is a fundamental aspect of life – for indeed DNA itself is a template of rules. The idea that nature uses algorithms has opened up new fields of investigation into the formation of nature's patterns.

Connectivity between an individual's nearest neighbors is essential if emergent behavior is to exist. For example, in the case of fish schools , the connection between individual fish is the effects of each individual's sensory organs that define proximity. The phenomena of emergent behavior is one form of proof that patterns in nature are connected.

Flocking, schooling, and herding are examples of the emergent behavior of a system resulting from self-organization. The enigma is that the system's emergent behavior can be more and different than that of any individual in the system. Yet, each individual in the system is using a feedback machine to receive sensory input, process the inputs according to a fixed set of rules, then act upon the result. It is the combined actions of all of the individuals using their feedback machines, that result in the emergent behavior of the system. Typically, a system that exhibits emergent behavior provides more complexity than the sum of its parts.

This spontaneous creation of order, is present all around us. Insects are a familiar example who manage to undertake massive building projects such as hives and mounds. Other species in the animal kingdom also display autonomous order. Fish move in concert organizing themselves into schools; birds and pack animals flock or herd in a similar manner. Nonliving examples of emergence include natural magnets that align themselves into a common North-South orientation. Crystals can form from liquids showing a spontaneous increase in order.

Certain systems flirt with the boundary between complete randomness and order - a term Christopher Langton, a leading researcher in emergent behavior, termed "the edge of chaos." What has ultimately become clear is that the generation of order manifested by patterns in nature is an inevitable product of the interaction of local elements in a system. Small changes in the rules that govern local interactions between neighbors can cause big changes in the pattern or order of the entire system. These type of systems, called "complex systems", are characterized by a sensitive dependence on initial conditions.

In the video shown below we see a living super-organism -- a real school of fish constantly changing shape as it responds to the actions of a predator. Yet, the behavior of the school is defined solely by the actions of individual fish who are each following a set of swimming rules that relate only to their nearest neighbors. This video is an example of how the emergent behavior of a system equals more than the sum of the parts.

An equally fascinating example of living emergent behavior is this video of birds in flight over Termini, Italy

Craig Reynolds, in 1986, developed a computer program called "Boids" to visualize and simulate flock behavior using three rules:

  • Maintain a certain minimum distance between nearby animals
  • Steer toward the approximate direction toward which the rest of the animals are heading
  • Move toward the average position of all the nearby animals

Shown below is a fish school computer simulation using the "boids" algorithms. Notice how this computer simulated school acts in much the same way as the real school shown in the previous video.

The visualization is surprisingly realistic given the simple nature of the instructions. "Boids" also demonstrates something interesting about the spontaneous creation of order. Self organizing patterns are very predictable over the short term, but completely unpredictable over the long term. It's easy to predict where a flock of birds will be in the next millisecond. But trying to predict the flock's speed and direction after looking away even for 10 seconds is nearly impossible.

PBS has provided excellent material on the subject of emergence. It offers ten examples of emergence. Shown below is the two part PBS video series on emergence.

Useful References


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