Table 1.

Properties of Complex Adaptive Systems

Property	Description	Notes
Nonlinearity	In nonlinear equations, the outputs are not proportional to their inputs.	Nonlinearity (1) can lead to sudden massive changes of the system and (2) is sensitive to initial conditions.
Attractor	An attractor is a point toward which a variable, moving according to the dictates of a dynamic system, evolves over time.	Points that get close enough to the attractor remain close even if slightly disturbed.
Open to environment	Living systems continuously interact with their environment, for example, exchanging material, energy, people, capital, and information.	In open systems, nonlinear responses to the external environment can lead to sudden massive and stochastic changes.
Self-organization	Self-organization is a process whereby some form of global order or coordination arises out of the local interactions between the components of an initially disordered system.	Self-organization relies on 4 basic principles: recursive feedback (positive and negative), a balance of exploitation and exploration, and multiple interactions.
Emergence	Emergence is the way in which complex systems and patterns arise out of a multiplicity of relatively simple interactions.	Emergence (1) arises from intricate causal relations across different scales and feedback (interconnectivity) and (2) the emergent behavior or properties are not a property of any single such entity, nor can they easily be predicted or deduced from behavior in the lower-level entities, that is, they are irreducible.
Pattern of interaction	All parts in a system involve predictable, repetitive processes.	Pattern of interaction can result from (1) different combinations of agents leading to the same outcome, or (2) the same combination of agents leading to different outcomes.
Adaptation and evolution	Adaptation is the process of change due to changes in the environment.	Evolution is the persistence of a change into the future. Adaptation and evolution (1) occur in numerous diseases over many years, during which time the whole body system adapts to function in the altered environment; (2) change the whole system and are not restricted to a few clinically measurable factors; and (3) lead to a new homeostasis with new dynamic interactions.
Coevolution	Coevolution is the change of an object triggered by the change of a related object.	Coevolution results in parallel development of a subsystem with new characteristics and dynamics.