[From Rupert Young (2015.02.15 20.15)]
On 05/01/2015 22:29, Rupert Young wrote:
[From Rupert Young (2015.01.05 22.30)]
(Rick Marken (2014.12.10.1045) (PCT robots)
RM: The other is what the beacon following robot does when there is no beacon present? Does it just go towards the brightest part of the room? Or does it stop? I'm interested because I've never really understood how a control system is taken "off line" and it looks like the beacon follower might only do its following when there is a beacon around.
I think this is an important question that we need to deal with, of how do control systems become active or inactive, and one I have been mulling over for a while. The beacon follower, with regard to distance, only works properly if the reference is zero. Then, when the perceptual signal is not present (it is zero) the output will also be zero. If, however, the reference is non-zero, 10 say, then when the perceptual signal is not present the error will be 10, and then robot will continually reverse, whereas the control system should deactivate. In this case there is no distinction between 0 as a signal value and 0 as a signal absence (null). So, there seems to be a need for the control system to become inactive. Technically this is not a great problem, but I am interested in how this would be viewed in PCT.
Traditionally this has been seen as the issue of attention, I think (actually Visual Attention was my initial topic on my PhD, before I discovered PCT). What is it that brings a system into attention? Does attention equate to a control system being active? What has happened to a previously active system? Is there a difference between a system which has achieved its goal and an inactive system (both of which have no output)? How does an inactive system become active (attention shift)? Can you have an active system when the perceptual input is null? Does the onset of a perceptual signal activate a control system? Does the onset of a reference signal activate a control system? Does the onset of a perceptual signal activate a reference signal? I will try to address some of these questions as I go on.
The attached shows a standard discussion of attention (though does include a vague inkling of PCT, see match condition on p68) but raises some interesting points on which we can expand for a PCT analysis. (From The Cognitive Approach to Conscious Machines by Pentti O. Haikonen).
Haikonen defines two types of attention, sensory and inner, and two subdivisions, voluntary and involuntary. So what would these mean in PCT terms?
Sensory involuntary - a shift in attention due to the onset of a perceptual signal such as movement in peripheral vision, or the cocktail party effect. This suggests the pre-existence of relevant control systems. For the former it could be a low-level, continually active system with the goal of equalising retinal motion, resulting in foveating the "stimulus". The latter is slightly different as it seems to require high-level context (memory) which provides significance. In this case then, is there a continually active system monitoring for the presence of one's name? This would imply that there would need to be active systems for everything of significance to a person. Or could the input itself in some way trigger activation of a control system, which results in attention?
Sensory voluntary - requires a goal for attending to a particular perception. For example, the thirsty man entering a room where there are a number of objects would want to attend to a bottle of water. So, he would have an existing goal for achieving water. But would he have to attend to each object in turn or would the water stand out from the scene due to the active water-desiring control system? That is, would the control system for a pie, say, be inactive as he is not hungry?
Inner involuntary - a shift in attention due to the onset of a reference signal. That is, activation of a control system due to top-down context rather than changes in perceptual input. Consider the situation of a dog with a juicy bone, but nearby is a man with stick. The man could be a threat with a stick to beat the dog or a friend throwing a stick to fetch. So the dog could either stay eating the bone or, depending upon context, run away or run after the stick. In both cases the perceptual input is the same, but the context depends upon whether or not the dog is afraid of the stick man; whether the run away system or the run after stick system is activated.
I'm not sure how useful these classifications are considering all involve references and perceptions (inner and sensory), thus "Sensory voluntary" seems to be the same as "Inner voluntary". The voluntary and involuntary division seems to indicate whether what you are currently controlling is interrupted or control passes to another system, perhaps in a sequence.
So, attention seems to describe that one system (at a particular level) is active to the exclusion of others (at the same level). And shift in attention describes that a system which was previously inactive becomes active, and the system that was active becomes inactive. And that shift (and activation) can be triggered by either a sensory onset or a reference onset.
Perhaps, then for a system to be active it is necessary for both the reference and perceptual signals to be present. We could then describe a number of different states of a control system, in terms of activation. In this context I mean inactive to indicate no output.
Inactive (dead) - Neither reference or perceptual signals are present.
Inactive (dormant) - Perceptual signal present, but not reference. When a reference signal becomes present this becomes active and the perceptual signal comes under control.
Inactive (monitoring) - Reference signal present, but not perceptual. This monitors for a certain perception but does nothing until that perceptual signal becomes present and then springs into action, e.g. when the beacon is turned on or there is a loud bang.
Active (controlling) - a system that is continuously controlling its perception according to its reference, and protects against disturbances.
Active (finished) - a system where the perception had been brought into line with the reference, but where there will not be any further change to perception or reference. In this case there will be no output, or no change in output.
So, there are a couple of questions here. One is how are inactive systems physically realised, when only one of either reference or perception is present?
And, two, what happens to a system that was active when it is interrupted? For example, if you are in a bar playing pool and you stop when a meaningful news item comes on the TV, what happened to your pool playing system? Is the reference switched off or suppressed? How does it switch back on when the news item is over?
Regarding one of the questions from the earlier list, "Does the onset of a perceptual signal activate a reference signal?" I can envisage how this might occur with a two-level system. Suppose they are both inactive, the top one monitoring and the lower one dead. Then a perception occurs which feeds up to the top system, which then becomes active producing output which sets the reference for the lower system which also becomes active.
Hmm, some rather muddled thoughts, so I'd welcome comments from others.