Powers and the Control Theory

As a psychologist and cybernetician, the American researcher William Powers had for many years pondered the question: ‘Why does the same disturbance sometimes result in different responses?’ The classical stimulus/response view and behaviourism had apparently failed to give an explanation. Powers himself gives the answer in his book Behavior: The Control of Perception (1973). Human behaviour is based on the concepts of control of reference perceptions and of feedback.

Powers illustrated his interpretation of these concepts with a small and ingenious metaphor: two rubber bands tied together with a knot. See Figure 3.26.

Figure 3.26 Illustration of feedback anInddceox ntrol by usreefof two rubber  bands.

(Reprinted with permission from: Powers, William T., Behavior: The Control of Perception. NefiwngYeorrk: Aldine de Gruyter. Copyright © 1973 by William T. Powers.)

Two persons, A and B, standing on opposite sides of a table put a finger into the loop formed when two rubber bands are tied together. They stretch the rubber bands and adjust the knot above an index on the table. If A now starts a small movement of his finger to displace the knot, B reacts and is able to maintain its position. The position of the knot as seen by B and related to the index on the table, is the controlled quantity, q.The position of B’s finger is the output quantity, Q. B’s rubber band represents the environmental feedback path, whereby B’s output affects his own input. The position of A’s finger represents the disturbance and his rubber band represents environmental links through which a disturbance affects the same controlled quantity affected by B’s output. Every aspect of the feedback control situation is thus both evident and explicit from the example.

Powers states that behaviour is governed by internal reference signals and that there exists a hierarchy of negative feedback control mechanisms which are discernible in a person’s behaviour. Within this hierarchy, the higher level mechanisms set the reference conditions

for lower levels and receive information about deviations in the comparison between controlled conditions and their reference values. Powers’ hierarchy of feedback control structures governs all kinds of human behaviour. This hierarchy of at least nine different levels is shown in Table 3.5.

In the hierarchy only the first-order level interacts directly with the surrounding world. Neurological evidence of the proposed control levels exists up to the fifth order and Powers also indicates where it resides anatomically. Above the fifth, the different levels are less distinct and must be traced in a more indirect way.

In all hierarchies of control, the lowest level system must have the fastest response. Adjusting reference conditions for lower level systems in order to correct own level errors must build upon the own slower performance and the performance of the lower system as well. Therefore, the higher the level in the hierarchy, the slower the adjustment and the longer the endurance of a disturbance. (While it is possible to see a clear correspondence between Beer’s and Powers’ hierarchies, on higher levels Powers’ seems more speculative.)

Ultimately, the behaviour of an organism is organized around its control of perceptions. Perceptions have no significance outside of the human brain. A presumed external reality is not the same as the experienced. Even if we acknowledge a real, surrounding universe, our perceptions are not that universe. They are influenced by it but its nature and impact is determined by the processing brain.

Reference signals for natural control systems (see Figure 3.27) are established inside the organism and cannot be influenced from outside. In Powers’ view, a natural reference signal can also be called purpose. If a perception does not match its internal reference, the result is a perceptual error. The higher the hierarchial level of this perceptual error, the greater the psychological distress. Something has to be done to reduce the error, something which quite simply can be called behaviour. Therefore, in Powers’ words: ‘What an organism senses affects what it does, and what it does affects what it senses.’


A more practical application of Powers’ model is found within the area of interpersonal conflict, defence and control. In Powers’ view, a conflict is an encounter between two control systems which try to control the same quantity, but according to two different reference levels. A conflict is only likely to occur between systems belonging to the same orders; systems of other orders have other classes of perceptions. Hence no single controlled quantity is shared. Levels of orders other than those in conflict will therefore behave normally. The psychological concept of cognitive dissonance seems to be compatible with Powers’ ideas with regard to this aspect.

A general model of the feedback/control system and the system’s local environment sum up Powers’ main train of thought in Figure 3.27. The nine levels are implicit.

Source: Skyttner Lars (2006), General Systems Theory: Problems, Perspectives, Practice, Wspc, 2nd Edition.

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