What perceptions are controlled by such a complex organism as a bacterium, a tree, a worm, or a person? It may seem odd to say that a bacterium controls its "perceptions", but remember the PCT definition of a perception: the value of some variable within an entity (e.g. a control unit) that corresponds to some state or complex of states outside the entity. Even the lowly e-coli bacterium (of which, more later) detects whether it is moving up or down a gradient of nutrient concentration, and varies its direction so as to "perceive" itself to be moving up-gradient.
To survive, any organism must maintain its internal chemistry within certain constraints. But how it can do so must depend on the environment in which the organism finds itself. One thing any human must do is eat. But the means to be in a position to eat are different if the person has to grow or hunt their own food or is in a position to buy it in a shop. Genetics can determine that the reference level for a control system controlling a perception of blood sugar levels should be thus-and-so, but genetics cannot possibly determine the reference levels for the perceptions involved in shopping for food. Accordingly, PCT incorporates a concept of "intrinsic variables" which have genetically determined reference levels in any given species.
The values of the intrinsic variables are affected by external disturbances and by the activities of the organism. Blood sugar is reduced as the cells burn sugar to get energy. The process increases the level of carbon dioxide in the blood, but the activity of breathing reduces that level while increasing the level of oxygen, which is used in the burning that energizes the body. There are many such loops, some well known, others yet to be discovered. They go all the way down to the mechanisms whereby the genes are expressed in the building of proteins, etc. We are not concerned here with those loops. But we are concerned with the larger-scale activities of the body, such as breathing, which was mentioned as a component of one loop. Or shopping, which in some environments could be equally important in keeping blood sugar levels where they should be.
If the perceptions involved in shopping serve to control the intrinsic variables, but many of the relevant control systems cannot be defined genetically, how can they be constructed? PCT suggests a mechanism called "reorganization."
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| These two figures represent (above) a global view of the relation between the intrinsic variables, the perceptual control hierarchy, and the common environment in which they both live; and (right) a local view of one hypothetical intrinsic variable that influences the relationships of some variables in the perceptual control hierarchy, the side-effects of which reduce the effect of a disturbance on the value of the intrinsic variable, or perhaps affect it directly. | |
| When a hierarchy of perceptual control systems is appropriately constructed, the side-effects of its controlling actions result in control of the intrinsic variables.The states of the intrinsic variables affect the structure of the perceptual control hierarchy by reorganizing it if its actions are ineffective; the perceptual control hierarchy's actions affect its environment, and the environment affects the intrinsic variables. The end result is a perceptual control hierarchy that controls perceptions that seem to have little to do with the intrinsic variables. The intrinsic variables are controlled indirectly. | |
Indirect control can work only in an environment that is sufficiently stable. In an unstable environment, both the actual side-effects and what the side-effects influence may change so that the actions involved in controlling any one perception may influence the intrinsic variables in one direction at one time, and in another direction at another time. On the other hand, if the environment is very stable, some aspects of the overt perceptual control could conceivably be built-in genetically. The laws of physics, for example, say that organisms living on solid ground will be subject to the pull of 1g of gravity. That fact has not changed for as long as life has existed on the Earth. It is a very stable aspect of the environment.
One aspect of "stability" is the stability of perceptual control. If control is not very good, the side-effects will be very variable, and the effect on the intrinsic variables will be inconsistent. If, for example, the transportation system fails and there is little food in the shops, control of the shopping perceptions relating to the perception of having food will be difficult, and the intrinsic variables relating to blood sugar may depart from their reference levels--in plain language, the person may starve. When the food supply is restored, the person's control for having (and eating) food is better, and even though the person does not perceive blood sugar level directly (unless the person is diabetic and has a blood-sugar measuring device), the acts involved in the perceptual control will bring the blood sugar level nearer to its evolutionarily determined reference level.
Stability of perceptual control is tightly linked to the quality of perceptual control. In discussions of PCT, it is often tacitly assumed that a measure of how well the perceptual control hierarchy is performing is one of the intrinisic variables. Indeed, we often consider "learning" to be based on the recognition of our inability to do something we want to do. This suggests that learning can be and often is based on the quality of control, but it also suggests that the quality measure is not an orthodox "intrinsic variable," since those normally cannot be perceived directly.
