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)
Multiple Data Sources
Multiple ECSs acting together can control percepts of arbitrary complexity.
ECSs do not work alone. Even though each one is responsible for controlling
its own perceptual signal, nevertheless the perceptual signals of many
ECSs are being controlled simultaneously. If there is a tendency for
events in the world to affect the perceptions of several ECSs together,
it is sometimes useful to think of the set of concurrently active ECSs
as forming a structured control system that controls a structured perceptual
signal—a multidimensional perceptual vector. This structured perceptual
signal need not have any reality for the functioning of the hierarchy
of control systems, but it is a useful concept for talking about the
hierarchy.
If a particular function of the vector of perceptual signals is important
to the organism, it is likely to be used as the perceptual input function
to a higher-level ECS, thereby being controlled directly.
The Perceptual Input Function (Data Fusion)
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The Perceptual Input Function (PIF) combines the sensory data from various aspects of the world in some way specific to itself. The result of this data fusion is a "Perception." The Commander sees only what his various PIFs allow him to see. They define relationships among aspects of the world called "Complex Environmental Variables" or CEVs. |
Any perceptual signal is the result of a data fusion process, in which a scalar value is obtained from a function of several sensory variables. The entire function is called the Perceptual Input Function (PIF). The form of the PIF determines a relationship among the values of some measurable aspects of the environment. That relationship is called a "Complex Environmental Variable" (CEV).
In most cases, the inputs to a PIF are the perceptual signals of lower ECSs. These perceptual signals are themselves the values of CEVs that correspond to the PIFs of the lower level ECSs (these three acronyms recur frequently in discussions of Perceptual Control Theory). Most CEVs, therefore, are composed of functions of other CEVs, in a hierarchy that mirrors the hierarchy of ECSs in the organism. Each CEV, at each level, is subject to disturbances.
The Mirror World: Perception and the outer world
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One cannot know the real world. One constructs it according to the available Perceptual Input Functions. What one perceives is a world structured so as to mirror ones own PIF hierarchy, and acted on by one's own output hierarchy. In other words, the world seems to consist of things at all levels of abstraction, and those things are controllable perceptions. The interpreter perceives that there exists a "mouse" although from another point of view there is only a collection of atoms of different types. The interpreter also perceives that there is a "situation," even though there are "only" soldiers and equipment on the ground, being detected through abstruse sensor systems, the outputs of which are reported by means of messages. |
Extra Data Sources and the Hysteresis of Perception:
Is the surface bubbled or dented?
In the talk, this slide was preceded by a photograph depicting a dented grey surface lit from the side. If the picture is interpreted as having the light come from the right, it looks as if the surface is bubbly, but if the light appears to come from the left, it looks dented. Normally, humans looking at this picture alternate between the two perceptions, but if the direction of the light is known, the interpretation becomes unique. Taylor and Aldridge (1974) were able to show that the timing pattern of perceptual changes was consistent with there being a small number of "interpreter" units independently asserting "bubbles" or "dents" and changing their opinions at random, with a "commander" unit that took a majority vote if the majority were strong enough, but otherwise retained whatever view it had previously held. The overt perception showed hysteresis.
The analogy with human commanders is clear; the commander should to some extent retain a concept of the situation, but should be open to contrary evidence, and should use extra evidence if it is available.