To begin with, as observed by L.A. ZADEH, "… all systems are adaptive, and the real question is what they are adaptive to and to what extent" (in G. KLIR, 1991 , p.143). Indeed, a nonadaptive system could not survive at all.
KLIR observes, furthermore, that even a goal-oriented system must maintain its goals within a range allowing for its own survival, "which implies that the (very) goal-seeking element must be capable of adaptation" (1991 , p.149)
It is also difficult to conceive an adaptive system that should not be endowed with at least a modicum of anticipatory behavior.
A. WILDEN establishes the following list of characteristics of adaptive systems, inspired by M.C. MARNEY and N.M. SMITH (1964):
1. Auto-differentiation or growth
2. Characteristic response: A response or a set of possible responses constrained by the limited semiotic liberty of the system. This response could be modified at the "learning to learn level" and also by evolution
3. Selectivity: The capacity of distinguishing stimuli information from noise, the form from the background.
4. Learning: Capacity of modifying the characteristic responses
5. Homeostasis: Synchronic stability within limits
6. Homeorhesis: Diachronic stability, of first order also within limits.
7. Redundancy: Protection of the system against random perturbations (implied in 5 and 6).
8. Memory: The sine qua non of communication, depending of the clues.
9. Simulation: Some form of behavior, mediatized by memory, application, reduction, semiotics, language, including the capacity of reproduction.
"This enumeration is not supposed to be absolutely complete, nor to establish ordered priorities among the mentioned characteristics" (WILDEN, 1972 ,p.61)
It may be objected that homeostasis, as well as homeorhesis, is diachronic, if one admits that the first word is synonym of dynamic stability. The difference between homeostasis and homeorhesis is that, while homeorhesis characterizes the growth period of the system, homeostasis is proper to its maturity (specially in biological systems), when the system only maintains, without wide modifications, its structures and functions within more or less narrow and invariable limits.
As to redundancy, it only protects the system if it can be used to enhance its variety or at least to reveal it.
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Bertalanffy Center for the Study of Systems Science (2020). Title of the entry. In Charles François (Ed.), International Encyclopedia of Systems and Cybernetics (2). Retrieved from www.systemspedia.org/[full/url]
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