[From Bill Powers (2006.06.19.0730 MDT)]
Wang Bo (2006.06.18) --
What's your opinion on how behaviours stored in the brain?
A series of supposed inputs and outputs��
Or a series of intended input?According to PCT, it seems to squints towards the second one. A sequence of intended inputs stored in brain. When the head of chain was actived(by some stimulus), every node generates output according to the intended input in it.
Or you have other ideas?
Yes, you are correct that PCT would be consistent with the second one. As you probably know, the control of sequences is just one level of organization that has been proposed. There are ten others, some at higher levels and others at lower levels. Only the lower levels have been put to any serious tests -- the rest are still only hypotheses based on informal observations.
However, the idea that an external stimulus activates a stored sequence is different from the PCT idea. In PCT, stimuli do not cause behavior, but just the opposite. The organism produces behavior (actions, movements, physical forces) as a means of causing perceptions to occur, and it adjusts the behavior to make the perceptions match internal "reference signals". Because the behavior acts on perceptions through the external world, and perceptions represent the external world, we can often observe aspects of the environment bing controlled when we see another organism behaving, expecially when we perceive in the same way that the observed organism perceives.
Independent external influences can change one or more perceptions that an organism is controlling, by acting on the world that the organism is sensing. Such influences are called disturbances. If a perception is being controlled, the organism will act to prevent it from changing, and this action will appear to be a "response" to a "stimulus". This is how the appearance of stimuli causing responses is explained in PCT. We identify such "stimuli" as disturbances of controlled variables.
At the sequence level of organization, the theory says, a sequence of perceptions would be stored as potential reference signals, like memories of the elements of the sequence. When a higher system specifies that a certain sequence is to be perceived, the organism will act (through lower-level systems) to create that sequence, matching the perceived sequence to the reference sequence. But in general, this will not result in a specific sequence of behaviors -- postures, movements, or forces -- because the environment normally is changing. Repeating the same sequence of actions will not cause the same sequence of results to occur. In order for a specific sequence of perceived results to occur, the actions must vary so as to compensate for variations in the environment. This is how the subject of negative feedback control arises in PCT. Only a negative feedback control system is able to alter its actions to keep the perceived result the same when unpredictable and invisible disturbances occur. Systems based on stimulus and response cannot do this.
I hope this is not ten times as much information as you wanted, and that I have at least partially answered your question. I would like to know what your interest in PCT is.-- can you tell us a little about yourself?
Best regards,
Bill P.