2.3 Self-organization Intuitively, self-organizing systems are those that produce a global pattern from the inter- actions of their components (Gershenson, 2007a). Classic examples include insect swarms, flocks of birds, and schools of fish (Camazine et al., 2003). Independently of their mecha- nism, it can be said that self-organizing systems are those that increase their organization in time from their own internal dynamics. As Ashby (1947b) noted, any dynamical system can be described as self-organizing, since they tend to attractors, and we only have to call those attractors “organized” to call the system self-organizing. Thus, self-organization depends partially on the purpose of the observer and the meaning she gives to the most probable states of a system. This does not imply that self-organization is purely subjective. Shan- non information can be used to measure organization: ordered, organized strings have less information than chaotic, disorganized strings. Gershenson & Heylighen (2003) proposed to measure self-organization as the negative of the change of information Δ I : if information is reduced, then self-organization occurs, while an increase of information implies self-disorganization. Nevertheless, it was shown that the same system can be considered as self-organizing or self-disorganizing, depending on the scale and on the partition of the state space (Gershenson and Heylighen, 2003). 2.4 Homeostasis Cannon (1932) defined homeostasis as the ability of an organism to maintain steady states of operation, in view of the internal and external changes. However, homeostasis does not imply an immobile or a stagnant state. Although some conditions may vary, the main properties remain relatively constant. Ashby (1947a; 1960) later recognized that homeostasis corre- sponds to an adaptive reaction to maintain “essential variables” within a range. Through adaptation, an organism develops the proper organization to function within a “viability zone”. This viability zone is defined by the lower and upper bounds of the essential vari- ables. In this sense, homeostasis is related with the capacity to remain within the viability 7