3. Perceptual Control Introduction
4. Perceptual Control and imagination
5. Hierarchic Perceptual Control
9. Degress of Freedom in the individual
10. Degrees of Freedom in the organization
11 Modes of Perception (Reprise)
The Bomb in the Hierarchy
The following sequence of slides illustrates one of the situations that lead to learning in an immature hierarchy. It is colloquially known as the Bomb in the hierarchy
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A normal ECS. Overall loop gain is negative, so that the ECS retains good control under normal environmental conditions. The sub-loop with positive feedback will probably not be detected. |
As we have seen, most ECSs control their perceptions through a feedback loop that consists of many intertwining threads. The CEV corresponding to the PIF has many elements that are affected by the output of the ECS. We can call the path through each of these CEVs at any level of abstraction a subloop, the set of all subloops at any given level being the complete feedback loop for the CEV. The feedback of the complete loop is negative, but this is not necessarily so of each of the constituent subloops. There may be some that would provide positive feedback if they were to be considered in isolation. But these are not normally detected in the operation of the hierarchy, since they are dominated by the negative feedback subloops.
| If for some reason, some of the effects adding to the negative feedback are blocked, the previously hidden positive feedback sub-loop may dominate, bringing the whole ECS into a positive feedback condition. It cannot control its perception. |  |
It is quite possible for the effect of any subloop to be blocked, perhaps because of conflict with another ECS that uses the same subloop, or perhaps because the effect in the world is blocked; one cannot drive one's car if the battery is flat one morning. If a blocked subloop is a major component of the negative feedback, then it may happen that a previously hidden subloop contributing positive feedback may become more important to the complete feedback loop. If it comes to dominate the complete feedback loop, the ECS may lose control of its perceptual signal (the overall feedback now being positive). The ECS behaves in a self-defeating manner. Moreover, it will provide uncontrolled perceptual signals to the sensory inputs of higher-level ECSs.
Persistent and increasing error in an ECS is one indication that the hierarchy needs reorganization. Something must change.
| Positive feedback in one ECS could conceivably propagate up to
higher-level ones that it supports, creating an avalanche of error
in the hierarchy. Common psychological effects: Anger, temper tantrum, self-destructive acts. |
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Each ECS has a place in the hierarchy. It supports other higher-level ECSs by providing them with perceptual signals that match the reference signals they send it. But if an ECS goes out of control because its feedback "braid" included a Bomb, it itself becomes a dangerous element in the feedback braid of the higher ECSs it supports. In the initial discussion of the Bomb, a previously hidden positive feedback subloop is revealed by the blockage of a parallel negative feedback subloop. Now the Bomb has introduced positive feedback in a subloop of its supported ECSs, where previously they had a negative feedback subloop. The supported ECSs are then susceptible to the Bomb themselves; their overall feedback will become positive if the other parts of their subloops cannot overcome the effect of the initial Bomb. There is an avalanche of destruction, in which successively higher levels of control are lost. The effect is akin to a temper tantrum of maladaptive behaviour.
- Why would a "Bomb" exist? Inadequate learning of multiple means of accomplishing an end.
- When would the "Bomb" show up? When some normally useful procedure fails for some reason.
- What would be the symptom of "Bomb?" Frustration, leading to inappropriate and maladaptive action.
- What is the result of the "Bomb" (assuming the organism survives)? Reorganization—learning new perceptions or new action connections in the hierarchy.
The Bomb could be disastrous in a complex hierarchy that did not have
a robust set of negative feedback subloops for most of its ECSs. In an
effectively functioning hierarchy, all or most of the active controllers
must have negative feedback, but this does not preclude the possibility
that changes in the environment may bring to light hidden Bombs, if the
hierarchy has not previously been exposed to that environment.
When a Bomb has exploded, it is likely that the hierarchy will have reorganized
in such a way that it is no longer susceptible to that kind of Bomb.
It has learned the new environment. It may have learned to control a
new perceptual signal by developing a new ECS, or its perceptions may
have subtly changed, or it may have learned new actions to control the
same perception. But it will have learned. An unstressed hierarchy may
contain many Bombs.
Common psychological stages when a Bomb goes off.
- Denial: Denying relevance of "new" way the world (mis)behaves, or of uncontrollable perception
- Anger: Consequence of failure of active control. Error signal grows at several control levels.
- Acceptance: Reorganization to revise structure or to modify perceptual input function.
- Adjustment: New structure reasserts control. Error signals diminish. Situation assessment now normalized and workload manageable.
There are commony accepted stages in reacting to a failure of perceptual control, and learning to reassert control. These are not themselves part of the Perceptual Control Theory, but they seem to correspond to phases in the reorganization process during and after the explosion of a Bomb in the hierarchy. At first, the hierarchy continues to act in its normal fashion, attempting to control a growing perceptual error (Denial). Then the growing error causes maladaptive behaviour at higher levels, as the avalanche of Bomb explosions grows (Anger). To correct the increasing error, reorganizations begins (Acceptance), and when it has been successfully completed, control can be re-established in the novel environment (Adjustment). Only then is it possible for the reorganized hierarchy to develop and maintain an effective level of situation awareness. At the same time, the fact that control has been re-asserted means that the effective workload has been reduced to a manageable level.
The Bomb may well be the primary means for an organism to learn to deal with a variety of environments and situations. A newborn baby can act in many ways, but those actions often fail to affect usefully the baby’s perceptions, though there are some control loops that seem to have been built in over evolutionary time. Quite soon, though, basic perceptions come under the baby’s control—hands pick up things, legs support the body, and so forth. These basic abilities are used under a wide variety of conditions. Imagine the problems a child would have if it had learned to walk only when facing a mirror, and the mirror were removed!
The same problems face a commander who has experienced only a small variety of situations. Actions that are appropriate against one kind of enemy may be disastrous when executed in another context. Failure to control perceptions is another way of saying that the battle is lost. Unless the Bombs are removed from the hierarchy, they are likely to explode, and almost by definition this will happen at the worst possible moment. By its nature, a Bomb explodes when the system is under stress, because only then are the negative feedback loops operating marginally, and only then is the loss of one contributor subloop likely to expose and explode the Bomb.
In competition, the opponent always tries to make one’s actions either ineffective or self-destructive. If Bombs remain, the competition is likely to uncover them, causing one to lose if the explosion avalanche proceeds too far up the hierarchy, as far as the perception whose control induces the competition itself. Conflict, remember, occurs when two control systems cannot simultaneously bring their perceptual signals to match their reference levels. If one of those control systems is Bombed, the other may well succeed.