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Emergence: Complexity from the Bottom Up

What is the compelling question or challenge?

How can we understand the ways in which complex behavior emerges from simple interactions? How can we harness these design principles to efficiently understand and create complex systems?

What do we know now about this Big Idea and what are the key research questions we need to address?

Under certain conditions, order seems to spontaneously emerge from disorder as though guided by a hidden director. The schooling behavior of fish, the intricate nature of frost crystals on a window, and the complex dynamics of enzymes within living systems are all examples of this unnerving and wondrous mechanism. These phenomena occur by a principle known as emergence, wherein parts of a system interact by simple mechanisms to either create complex collective behavior impossible for any individual component, or generate spontaneous order from disorganized components. This mechanism is ubiquitous in nature because it builds complexity with extreme efficiency. The complex system is built from simple components, but it is fundamentally more than the sum of its parts, because of these interactions.

In the example of frost, the structure of water molecules allows them to form strong intermolecular “hydrogen bonds,” causing them to form a highly-ordered crystal structure (ice) to facilitate these interactions in cold temperatures. Without this fundamental interaction, disorganized water molecules in the air would form disorganized crystals unless each molecule was picked out of the air in placed into an organized structure one by one, and the result would be far less beautiful. Another example is enzyme function. Enzymes are known for their complex and highly-specialized behavior resulting from the interactions of many amino acids linked together. The chemical reactivity of each of these amino acid residues is simple, but when linked together, they cause complex folding of the chain and collectively change the interior environment of the enzyme to dramatically expand the abilities of each residue. These inter-amino acid interactions are responsible for the extraordinary sophistication of enzymes. These are well-understood examples, but many important systems have not yet been elucidated.

Our current scientific disciplines are adept at examining the interactions among the base components of the system (amino acid reactivity, chemical hydrogen bonding, etc.) but are often unable to trace the effects of these interactions over length and time scales to the predict the complex communal behavior which we observe. For example, neuron firing is well-understood, but the level at which consciousness emerges remains a mystery. The ability to analyze large amounts of data has been a boon to this effort, allowing functional assignments for many regions of the brain, but it is still a protracted effort to determine the role played by each component of the system (neuron/brain area) in the eventual behavior of the whole (the mind), and many other systems similarly remain too large to understand by this brute force method.

As a scientific community, we must investigate the ways in which components of the system transmit information to produce complex behavior and order across length scales. This will involve categorizing the types of ways in which components communicate information (chemical, social, etc.), and the dynamics of this communication (range, time dependence, error). Then we must endeavor to understand the way these interactions affect other components and other interactions, and so on, in this way developing a system for generating complexity one level at a time. Once the development of many complex behaviors from the level of fundamental elements is understood, the extraction of general design principles for creating spontaneous order and behavior is possible.

Recently, “complex systems science” has emerged to deal with these questions, but it incorporates only a fledgling notion of emergence and lacks a standardized formalism to allow for merging of multidisciplinary insight into a unified approach. Bedau (1997) is one of the few who have written on this topic in versatile terms. This framework must be extended and fortified before it can answer the questions posed above.

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