Complex adaptive systems, are a special case of complex systems. They are complex in that they are diverse and made up of multiple interconnected elements and adaptive in that they have the capacity to change and learn from experience. The term complex adaptive systems was coined at the interdisciplinary Santa Fe Institute (SFI), by John H. Holland, Murray Gell-Mann and others. John H. Holland is one of the inventors of evolutionary computation and genetic algorithms. Nobel Prize laureate Murray Gell-Mann discovered quarks. Complex systems have a number of properties, some of which are listed below. ... The Santa Fe Institute [SFI] is a non-profit research institute in Santa Fe, New Mexico founded by Murray Gell-Mann in 1984 to study complex systems and disseminate the notion of a separate interdisciplinary study of complexity theory. ... Murray Gell-Mann at Harvard University Murray Gell-Mann (born September 15, 1929) is an American physicist who received the 1969 Nobel Prize in physics for his work on the theory of elementary particles. ... ... A genetic algorithm (GA) is a search technique used in computer science to find approximate solutions to optimization and search problems. ... This article does not cite its references or sources. ... Quarks are one of the two basic constituents of matter in the Standard Model of particle physics. ...

The term complex adaptive systems (or complexity science) is often used to describe the loosely organized academic field that has grown up around the study of such systems. Complexity science is not a single theory— it encompasses more than one theoretical framework and is highly interdisciplinary, seeking the answers to some fundamental questions about living, adaptable, changeable systems.

Examples of complex adaptive systems include the stock market, social insect and ant colonies, the biosphere and the ecosystem, the brain and the immune system, the cell and the developing embryo, manufacturing businesses and any human social group-based endeavour in a cultural and social system such as political parties or communities. There are close relationships between the field of CAS and artificial life. In both areas the principles emergence and self-organization are very important. The New York Stock Exchange The stock market is the market for the trading of company stock, and derivatives of same; both those securities listed on a stock exchange as well as those only traded privately. ... Subfamilies Dorylomorph subfamilies Apomyrminae Cerapachyinae Dorylinae Ecitoninae Formicomorph subfamilies: Aneuretinae Dolichoderinae Formicinae - e. ... The biosphere is that part of a planets outer shell—including air, land, surface rocks and water—within which life occurs, and which biotic processes in turn alter or transform. ... In ecology, the word ecosystem is an abbreviation of the term, ecological system. ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), acts as the control center of the central nervous system. ... The immune system is the system of specialised cells and organs that protect an organism from outside biological influences. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... Embryos (and one tadpole) of the wrinkled frog (Rana rugosa). ... This article needs to be cleaned up to conform to a higher standard of quality. ... Social structure (also referred to as a social system) is a system in which people forming the society are organized by a patterns of prelationships. ... A political party is an organization that seeks to attain political power within a government, usually by participating in electoral campaigns. ... This article needs a complete rewrite for the reasons listed on the talk page. ... Artificial life, also known as alife or a-life, is the study of life through the use of human-made analogs of living systems. ... A termite cathedral mound produced by a termite colony: a classic example of emergence. ... Self-organization refers to a process in which the internal organization of a system, normally an open system, increases automatically without being guided or managed by an outside source. ...

Definitions

A CAS is a complex, self-similar collection of interacting adaptive agents. The study of CAS focus on complex, emergent and macroscopic properties of the system. Various definitions have been offered by different researchers:

• John H. Holland

A Complex Adaptive System (CAS) is a dynamic network of many agents (which may represent cells, species, individuals, firms, nations) acting in parallel, constantly acting and reacting to what the other agents are doing. The control of a CAS tends to be highly dispersed and decentralized. If there is to be any coherent behavior in the system, it has to arise from competition and cooperation among the agents themselves. The overall behavior of the system is the result of a huge number of decisions made every moment by many individual agents. (source: Complexity: The Emerging Science at the Edge of Order and Chaos by Michael Waldrop)

• Kevin Dooley

A CAS behaves/evolves according to three key principles: order is emergent as opposed to predetermined (c.f. Neural Networks), the system's history is irreversible, and the system's future is often unpredictable. The basic building blocks of the CAS are agents. Agents scan their environment and develop schema representing interpretive and action rules. These schema are subject to change and evolution. (source: K. Dooley, AZ State University) Simplified view of an artificial neural network A neural network is an interconnected group of biological neurons. ...

• Other definitions

Macroscopic collections of simple (and typically nonlinearly) interacting units that are endowed with the ability to evolve and adapt to a changing environment. (source: Complexity in Social Science glossary a research training project of the European Commission) The European Commission (formally the Commission of the European Communities) is the executive of the European Union. ...

Properties of CAS

What distinguishes a CAS from a pure multi-agent system (MAS) is the focus on top-level properties and features like self-similarity, complexity, emergence and self-organization. An MAS is simply defined as a system composed of multiple, interacting agents. In CASs, the agents as well as the system are adaptive: the system is self-similar. A CAS is a complex, self-similar collectivity of interacting adaptive agents. In computer science, a multi-agent system (MAS) is a system composed of several agents, capable of mutual interaction. ... A self-similar object is exactly or approximately similar to a part of itself. ... Complexity is the opposite of simplicity. ... A termite cathedral mound produced by a termite colony: a classic example of emergence. ... Self-organization refers to a process in which the internal organization of a system, normally an open system, increases automatically without being guided or managed by an outside source. ...

Other important properties are adaptation (or homeostasis), communication, cooperation, specialization, spatial and temporal organization, and of course reproduction. They can be found on all levels: cells specialize, adapt and reproduce themselves just like larger organisms do. Communication and cooperation take place on all levels, from the agent to the system level. Homeostasis is the property of an open system, especially living organisms, to regulate its internal environment to maintain a stable, constant condition, by means of multiple dynamic equilibrium adjustments, controlled by interrelated regulation mechanisms. ...

Graphic

Download high resolution version (2100x1500, 380 KB)  Acadac was inspired to create this graphic after reading: Roger Lewin (1992) Complexity: Life and the Edge of Chaos Steven Johnson (2001) Emergence: The Connected Lives of Ants, Brains, Cities, and Software   File links The following pages link to this file: Emergence Complex...

Researchers and scientists

• Prof. Ozalp Babaoglu, University of Bologna
• Prof. Stephanie Forrest, University of New Mexico
• Prof. Melanie Mitchell, Portland State University

 Dr Elizabeth McMillan, DPP, Open University, Milton Keynes, UK 

See also

Dr Elizabeth McMillan, Open University, Milton Keynes, UK

• Santa Fe Institute

The Santa Fe Institute [SFI] is a non-profit research institute in Santa Fe, New Mexico founded by Murray Gell-Mann in 1984 to study complex systems and disseminate the notion of a separate interdisciplinary study of complexity theory. ...

External links

• CAS Group at Iowa State University
• CAS Research Site by Mark Voss
• Plexus Institute - An organization dedicated to bringing the benefits of complex adaptive systems to the world
• Santa Fe Institute - The Santa Fe Institute is devoted to creating a new kind of scientific research community, one emphasizing multidisciplinary collaboration in pursuit of understanding the common themes that arise in natural, artificial, and social systems. This unique scientific enterprise attempts to uncover the mechanisms that underlie the deep simplicity present in our complex world.
• A description of complex adaptive systems on the Principia Cybernetica Web (a project that aims to develop a complete philosophy or worldview, based on the principles of evolutionary cybernetics, and supported by collaborative computer technologies)
• A quick reference single-page description of the 'world' of complexity and related ideas hosted by The Center for the Study of Complex Systems at the University of Michigan
• Yahoo! CAS Group
• RedFish Group
• Center for Complex Systems and Brain Sciences at Florida Atlantic University an Interdisciplinary center which seeks to understand the brain as a complex adaptive system
• ThinkVine LLC - Complexity science applied to marketing problems.