Attempted in systems of biological size and complexity ? What hap-
Pens, for instance, when regulation and control are attempted in the
Brain or in a human society?
Discussion of this question will occupy the remaining chapters.
Fig 12/22/1
Fied channels Ii and then acts determinately on M. The site of
connexion of the I’s is defined by Γ . Effects from each T,
Together with those of the other T’s and the V’s, exert, through M,
Complex controls over the dials G. When the play, i.e. trajectory,
Is completed, the umpire H reads the G’s and then makes corre-
Sponding payments to the T’s.
What we have here is evidently the case of several regulators,
Each trying to achieve a goal in G, working simultaneously, and
Interacting competitively within M. (The possibility of competi-
Tion between regulators has not been considered explicitly in these
Chapters till now.)
If the system is ultrastable, each T’s behaviour will be deter-
Mined by parameters, behaving as step-functions. If a particular
Player is “satisfied” by the payment from H, his parameters will
242
243
RE GU LA TI N G TH E V ER Y LA R GE SY STE M
Chapter
13
R E G U L A TIN G T H E V E R Y L A RG E
SYSTEM
Regulation and control in the very large system is of pecu-
Liar interest to the worker in any of the biological sciences, for
Most of the systems he deals with are complex and composed of
Almost uncountably many parts. The ecologist may want to regu-
Late the incidence of an infection in a biological system of great
Size and complexity, with climate, soil, host’s reactions, preda-
Tors, competitors, and many other factors playing a part. The
Economist may want to regulate against a tendency to slump in a
System in which prices, availability of labour, consumer’s
Demands, costs of raw materials, are only a few of the factors that
Play some part. The sociologist faces a similar situation. And the
Psychotherapist attempts to regulate the working of a sick brain
That is of the same order of size as his own, and of fearful com-
Plexity. These regulations are obviously very different from those
|
|
|
Considered in the simple mechanisms of the previous chapter. At
First sight they look so different that one may well wonder
Whether what has been said so far is not essentially inapplicable.
This, however, is not so. To repeat what was said in S.4/18,
Many of the propositions established earlier are stated in a form
That leaves the size of the system irrelevant. (Sometimes the
Number of states or the number of variables may be involved, but
In such a way that the proposition remains true whatever the
Actual number.)
Regulation in biological systems certainly raises difficult prob-
Lems — that can be admitted freely. But let us be careful, in admit-
Ting this, not to attribute the difficulty to the wrong source.
Largeness in itself is not the source; it tends to be so regarded partly
Because its obviousness makes it catch the eye and partly because
Variations in size tend to be correlated with variations in the source
Of the real difficulty. What is usually the main cause of difficulty is
The variety in the disturbances that must be regulated against.
The size of the dynamic system that embodies T tends to be corre-
244
Lated with the variety in D for several reasons. If T is made of many
Parts, and there is uncertainty about the initial state of any part, then
That variety will be allocated to D (S. 11/19); so in general, other
Things being equal, the greater the number of parts the greater the
Variety in D. Secondly, if each part is not completely isolated from
The world around, each part’s input will contribute some variety
Which will be allocated to D; so in general, the greater the number of
Parts the greater the number of components in D; and therefore, if
The components have some independence, the greater the variety in
D. (There may be other reasons as well but these will suffice.)
|
|
|
Thus, when the effects of size are distinguished from those that
Affect the variety in D, it will usually be found that the former is,
In itself, irrelevant, and that what matters is the latter.
It now follows that when the system T is very large and the
Дата добавления: 2019-11-16; просмотров: 212; Мы поможем в написании вашей работы! |
Мы поможем в написании ваших работ!