Indirect Control

One control unit can have effects that alter the ability of another to control. One way this can happen is that the actions of one control unit affects not only the environmental variable defined by its own perceptual function, but also the disturbance that impinges on the CEV of the other. This may be because there is some overlap between the CEV of one and source or transmission route of the disturbance of the other. But it could also be because the side-effects of one might inhibit the disturbance to the other.

Here is a real-world example. One possible perception controlled by a person might be to perceive oneself as having food. If there were no farmers, and everyone grew their own food, that perception would be greatly disturbed by the vagaries of the weather. Another perception that people might control is to have money. Farming is (or used to be) a way to influence the amount of money one has. By growing and selling food, the farmer controls a perception of having money.

A side-effect of the farmer's control of the "having money" perception is that (by means of various other people controlling other perceptions) food appears in stores. The consumer has a means of controlling a perception of having food that is less subject to the vagaries of the weather than is home gardening.

The weather still can disturb the consumer's control of the "having food" perception, since it affects the price of food in the store. But the weather has much less disturbing effect on the consumer's ability to have food than it would if the farmer were not controlling for having money.

The influence of each control system on the other is through side-effects. The farmer cannot perceive any one consumer, and therefore cannot control any perception related to the consumer. An outside analyst may observe both farmer and consumer, and may note that if the farmer does not produce what the consumer wants, the consumer will not buy, but all the farmer can see of this is that some crops are more effective than others in bringing in money. According to PCT, the farmer is likely to reorganize to increase the financial effectiveness of crop production. The consumer, meanwhile, cannot perceive the farmer, and buys food rather than growing it because that is a more effective way of controlling the "having food" perception--it takes less time, perhaps, and it certainly is less disturbed by variations in the weather.

Farmer and consumer are, in a way, bound together by the side-effects of each other's control mechanisms. If either stopped controlling those perceptions, or started to control them by other means (such as the farmer giving up farming and starting to work on an assembly line making cars to get money), the other would find it much more difficult to control their own perception. But neither directly perceives the effects on the other of their control actions, and therefore the effects are pure side-effects. It is through these and similar side-effects that society as a whole hangs together.

Side-Effect Disturbance.

The action vector (in the Outer World) of one unit is correlated with the perceptual vector of another, even though the two perceptual vectors may themselves be orthogonal. The side-effects of one act as simple disturbances to the other. This is very common. Above, side-effects are shown to be possibly helpful, but it is much more likely that what one person does will directly disturb the perceptions of another.

Conflict.

The perceptual vectors of the two units are correlated, so that any attempt by one to control its perception will disturb the other. If there are enough degrees of freedom available to the two control loops, each is likely to be able to retain control, but if the two perceptual vectors are actually parallel in "Outer World Space" (i.e. the two units are trying to control the same variable at different reference values), conflict will occur--and because many control units have output functions that integrate the error, conflict will escalate.

Hierarchy.

The reference value of one control system may be determined (or influenced) by the output signal from another, and it may feed its perceptual signal back to the other's perceptual input function. The "higher" unit determines what perceptual input value it wants to see, and the "lower" unit provides that value to the best of its ability, thereby shielding the higher unit from disturbances that might otherwise buffet it. In a more complex hierarchy, several lower units each contribute to the perceptual signals of several higher units, and the reference values of the lower units are derived from the outputs of all the higher units.

Very occasionally, in a large set of control units, it may happen that the actions of one serve to shield the perception of another from some disturbance (recall the example of the farmer and consumer earlier). If this happens, the shielded unit will be better able to control against the remaining disturbances than it would otherwise have been. Such an arrangement will therefore be likely to be stable against reorganization (the winter-leaf phenomenon; the wild wind may remove some leaves from a drift-pile, but with a lower probability than that it will blow a leaf off a bare patch of ground).

Interference and shielding are two ways control units can interact. How strongly they interact may be thought of as a kind of "coupling constant." The notion of coupling constant is very important in what follows.