International Encyclopedia of Systems and Cybernetics

The property of a system which does not return to its original state when submitted to a variation.

N. RASHEVSKY explains that hysteresis result of the fact: "… that the properties and reactions of a system are determined not merely by its present surroundings but also by the conditions of these surroundings at previous times, or, in other words, that those properties are determined by the past history of the system" (1960, p.69).

The classical example of hysteresis in physics is the failure of a magnetized body to return to its former level of magnetization when the value of the magnetic field is reduced. However the phenomenon is very general. RASHEVSKY states: "From this point of view, various phenomena in the central nervous system, such as those connected with learning, adaptation, etc. are merely complex forms of hysteresis" (Ibid).

This connects the subject with autopoeisis.

R. ROSEN explains: "A system exhibiting hysteresis has the capacity to "remember", in a certain sense, that it was exposed to a parameter variation, in that the behavior of such a system will generally be different from that of an identical system which was not exposed to the parameter variation. Indeed, in biology hysteresis has often be used, implicitly or explicitly, as a model for short-term or long-term memories".

Of course, there are no "identical" systems, but this semantic lapse does not annulate ROSEN's argument.

He states, moreover, that it is often possible to "erase" the memory of such a perturbation "… provide we can reduce the parameter P sufficiently below the original value P = P₀; this gives rise to the well-known concept of the hysteresis loop. But it is by no means always possible" (1974, p.98).