Complex Adaptive System (CAS)

Government officials and other decision makers increasingly encounter a daunting class of problems that involve systems composed of very large numbers of diverse interacting parts (Shalizi, 2006). These systems are prone to surprising, large-scale, seemingly uncontrollable behaviors. These traits are the hallmarks of what scientists call complex systems. A complex system is composed of many parts that interact with and adapt to each other and, in so doing, affect their own individual environments. The combined system-level behavior arises from the interactions of parts that are, in turn, influenced by the overall state of the system. Global patterns emerge from the autonomous but interdependent mutual adjustments of the components (Jacobson et al., 2011).

According to John Holland CAS is a special category of complex systems dealing with living systems that have the capacity to change, learn from experience and sometimes forecast (Holland, 1999). The control of a CAS tends to be highly dispersed and decentralized. If there is to be any coherent behavior in the system, it will have 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. (Holland, 1992, p. 17). Typical phenomena in complex adaptive systems are the emergence of macro-level structures due to interactions at the micro-level (self-organisation). These macro-structures in turn determine the behavioural freedom at the micro-level (downward causation).

Related terms: Complex System

References:

Holland, J. H. (1992), Complex Adaptive Systems, Daedalus, Vol. 121(No. 1), pp. 17-30.

Holland, John H. (1999), Emergence: from chaos to order, Reading, Mass: Perseus Books.

Jacobson, M., Kapur, M., So, H.-J., & Lee, J. (2011). The ontologies of complexity and learning about complex systems. Instructional Science, Vol. 39(No. 5), pp. 763-783. doi: 10.1007/s11251-010-9147-0

Shalizi, C. R. (2006). Methods and Techniques of Complex Systems Science: An Overview Complex Systems Science in Biomedicine. In T. S. Deisboeck & J. Y. Kresh (Eds.), (pp. 33-114): Springer US.