Bill's "insight" Posting (was Re: World Model...)

[Martin Taylor 2015.04.25.14.05]

Actually, Rick was right, but so was I. We both ignored what the

other saw. Bill was talking about both a model of the way the world
works AND a model of the way the world is perceived. I think the reason I didn’t see the bit about creating new
perceptual functions and modifying others to work better in the real
world was that for me it is a very old idea, that I learned first
from Jim Taylor (J. G. Taylor, “The Behavioral Basis of Perception”,
Yale UP, 1963, which I reviewed when it was first published). Jim,
by the way, is no relation, although I came to know him quite well
after he retired from Capetown University and came to work at the
same institute as me, largely because of my review. I contributed a
paper that I have sometimes mentioned on CSGnet to a Festschrift in
honour of the tenth anniversary of the book
.
JG’s theory was that we learn to perceive whatever functions of our
sensor inputs are required for behaving in the real world, through a
whole mess of feedback loops. If we form perceptual functions not
used in behaving, those functions would be lost. If we needed new
perceptual functions and the data were available, we would be
likely, but not certain, to build them. JG was a Hullian
reinforcement theorist from a clinical research background, but I
rather think that if he and Bill had got together they would have
converged views very quickly, JG to embrace PCT, and Bill to build
working models of the development and modification of perceptual
functions in the hierarchy. What Bill says at the beginning and near
the end of tie “Insight” message sound to me as though Bill would
have arrived at JG’s theory, properly embedded within PCT.
Here’s Bill’s message, complete.
Martin

···

I thought that since this posting has
been a topic of discussion, it might be worthwhile to repost it. I
will add it after my comments.

[Martin Taylor 2015.04.25.10.41]

http://www.mmtaylor.net/Academic/SouthAfricanJ_OCR_edit.doc

Insight into PCT models

    From Bill Powers

(2010.12.22.2300 MDT)]

    Something is coming together that is making sense of some ideas

I

    have resisted for a long time. It has to do with the brain's

models

    of the external world. From the way I have seen those models

proposed

    by others such as Ashby and Modern Control Theory adherents, I

have

    thought they were simply impractical, calling for far too much

    knowledge, computing power, and precision of action -- as indeed

they

    are and they do, as they have been presented.

    But those ideas may nevertheless be right. Some of those other

blind

    men standing around the elephant are perhaps only a little

    nearsighted, and are seeing something going on that looks

fuzzily

    like modeling, but there's something funny about it so it isn't

quite

    how it seems from this angle or that. This particular blind or

    nearsighted man writing these sentences has not seen models; he

has

    seen a hierarchy of perceptions that somehow represents an

external

    world, and a large collection of Complex Environmental Variables

(as

    Martin Taylor calls them) that is mirrored inside the brain in

the

    form of perceptions.

    Briefly, then: what I call the hierarchy of perceptions is the

model.

    When you open your eyes and look around, what you see -- and

feel,

    smell, hear, and taste -- is the model. In fact we never

experience

    ANYTHING BUT the model. The model is composed of perceptions of

all

    kinds from intensities on up.

    Warren Mansell asked some questions about feedback and

feedfoward

    that stirred a few thoughts up. I think his ambition to

integrate

    different ideas people have had about control theory suddenly

looked

    more appealing than before. I've been working on and thinking

about

    how to get a better fit of the current tracking model to the

real

    behavior, and that has stirred up a lot more thoughts. I was

thinking

    about how to add a two-level controller in which the upper level

    controls position and the level below controls rate of change

(yes, I

    know that's backward). I realized that I would need a sensor

that

    senses rate of change of position, and that, in turn, called to

mind

    the neat analog-computing techique that computes first

derivatives by

    putting an integrator in the feedback path of a little control

system

    -- it's actually described in LCS3, chapter 5.

    I considered using that method to implement a new model for the

    TrackAnalyze program and for some reason didn't like the idea of

    doing it that way. Then the reason dawned on me: I was actually

    proposing to put a model of the physical environment into my PCT

    model, and I'm not supposed to be in favor of doing that. But it

    happens that if you integrate the force applied to a mass, the

value

    of the integral represents the velocity, which keeps changing in

    proportion to the force. The velocity is the first derivative of

    position. The factor applied to the force as it is being

integrated

    represents the reciprocal of the mass of the object being pushed

    upon. So I was proposing to put a model of the mass of an arm,

    together with Newton's laws of motion, into my sacred PCT model.

    So: I was thinking of sticking a model into my model, between

the

    output and the input, as a convenient way of getting a signal

that

    would represent velocity. It would be generated by applying a

force

    to a simulated mass. So the arm controller would sense the force

its

    muscles were producing and integrate the force to create a

    synthesized perception of the velocity, and then it would have a

    controller for controlling that integrated perception and we

would

    have one level of control.

    But wait. Where did that model come from? Don't we need to

control

    through the real world outside? It came from applying perceived

    forces to perceived things and -- for one example -- seeing them

    move. A kinesthetically detected output force becomes a

perceptual

    signal representing force; the force signal is integrated to

produce

    a visual perception of changing velocity; a visual perception of

    velocity is integrated to produce a visual perception of

position,

    and a changing velocity produces a perception of acceleration.

And

    this is all happening inside the nervous system. In a model.

    The modern control theorists came closest to seeing how this

works.

    They said that the internal model was carefully constructed to

have

    the same properties as the external "plant" that was to be

    controlled. Then the brain could work out, internally, what

signal it

    had to send into the model to make it behave in a certain way,

and

    when it had that working, it could send the same signal to the

    external "plant" and it would behave the same way. They admit

that to

    make this work the model of the plant has to be rather

dauntingly

    accurate, and every disturbance has to be accurately anticipated

as

    to size, direction, and time of occurrance.

    So the picture I got was that the brain supposedly had the

ability to

    examine the plant and measure its properties, and then

constructed a

    computed model inside itself based on the data thus obtained.

But of

    course I knew that the brain can do no such thing: all it knows

are

    the perceptions it gets, and it has no way to compare them with

the

    real plant Out There to see if it got the measurements right.

    Everything it does has to be done with the perceptions, not with

the

    real plant.

    That is where I had always stopped before, just prior to

discarding

    the model-based control idea once again. But for some reason,

this

    time I kept going.

    We can sense output force because the tendons have sensors that

    report how hard the muscles are pulling, and we have pressure

sensors

    all over that detect how hard a hand or foot is pressing against

    something else. We have sensors to tell us if a joint angle is

    changing as a result of the force, and of course we have vision

to

    give a different spatial view of the result. So by experimenting

with

    output forces, we can build up a set of control systems for

    controlling the immediate consequences of applying forces. We

can get

    to know how much consequence a given amount of force produces.

Years

    later we will learn that the ratio of force to consequence is

called

    "mass." But if we integrate the force to produce a velocity, we

can

    discover empirically what the value of this ratio is for

different

    objects, without calling it anything.

    That is all we need to do to build up a model of the external

world.

    It's not even that; it's just a model of the world. The idea

that

    there's also an external world that we don't experience takes a

while

    to develop. At first it's just the only world there is.

    So that is the model that Ashby and the Modern Control Theorists

are

    talking about. It's the world we experience. When we examine

that

    external plant in order to model it, we're already looking at

the

    brain's model. It lacks  detail, but as we probe and push and

peer

    and twiddle and otherwise act on these rudimentary perceptions,

new

    perceptions form that begin to add features and properties --

like

    mass -- to the model. We say we are analyzing the plant. What we

are

    doing is building up perceptions of properties and features that

can

    be affected by sending signals outward, learning how to control

the

    perceptions. Why we have to act one way instead of another to

get a

    particular  effect is unknown, but we learn the rules. When we

don’t

    get the effect we want, we alter what we are doing until we do

get it.

    We never do actually, knowingly, interact with the plant itself.

    It seems very risky to be operating entirely on an internal

model

    without any ability to know what is really going on that we

can’t

    see, but really, it's not. Before you step into the bathtub you

feel

    the water, so if you've made a mistake you're not going to scald

your

    whole body. We detect errors very quickly and make adjustments

almost

    as quickly to limit the errors, and eventually to keep them from

ever

    getting very large. We're always interacting with whatever is

Out

    There, and we learn fast. Most of us. most of the time, don't

even

    think about the invisible universe Out There. The visible one is

    sufficient to keep us busy and interested. The idea that there's

    another bigger one that actually determines what the rules are

    doesn't usually arise.

    I'm beginning to get an idea now about how to model perceptions,

at

    least at the lower levels. All we have to do is make a model of

the

    environment, just like that analog-computing trick for

calculating

    rates of change by using integrators, which turns out to embody

    Newton's laws of motion. This whole idea is still very new and I

    don't see very far along the path ahead, but I have a feeling

that

    what looked very difficult before may start getting a little

less difficult.

    I'd better get to bed; it's very strange to look around at this

room

    and think "This is my model. I, or something in me, constructed

every

    detail in it, all the things I recognize and know about it and

can do

    to it. Help, is this solipsism?"

    But no, it's not. Solipsism says there really isn't anything

else. We

    can freely assume that there is a huge lawful universe full of

    regularities, as long as we realize that all we will ever

experience

    of it is the model that we build in our brains. When it does

what we

    call raining we get what we call wet, but we can only assume

that

    those experiences occurring in our models correspond in some

    unknowable way to whatever else there is.

    I hope all of this doesn't evaporate overnight.

    Best,

    Bill P.

    On 2015/04/25 12:23 AM, Richard

Marken ( via
csgnet Mailing List) wrote:

rsmarken@gmail.com

[From Rick Marken (2015.04.24.2120)]

              Martin Taylor

(2015.04.24.17.22)–

                                          RM: I don't think the

imagination connection has
anything to do with it.
There is certainly no
mention of it in Bill’s
quote. The “model’” Bill
was talking about (as he
said) IS the hierarchy of
perception so it starts at
the lowest level.

                              MT: No, I disagree. Read it

again – the whole thing, if you want.
Bill was talking about a model of “The
way the world works”.

[From Rick Marken (2015.04.28.0900)]

···

Martin Taylor (2015.04.25.14.05)

  MT: I thought that since this posting has

been a topic of discussion, it might be worthwhile to repost it. I
will add it after my comments.

RM: Thanks for this Martin. I think the first paragraph is still the most important:

    BP:Something is coming together that is making sense of some ideas

I

    have resisted for a long time. It has to do with the brain's

models

    of the external world. From the way I have seen those models

proposed

    by others such as Ashby and Modern Control Theory adherents, I

have

    thought they were simply impractical, calling for far too much

    knowledge, computing power, and precision of action -- as indeed

they

    are and they do, as they have been presented.

RM: Bill is saying that control models like those of Ashby and MCT that contain models of the external world – what they call “world models” – are “impractical” as they have been presented. So Bill is rejecting the way “world models” exist in Ashby/MCT control models. In the Ashby/MCT control models the “world models” are like scientific models of the way the external world works; they are inside the control model itself and used as part of the control process to predict the effect actions will have on variables in the external world. This is the kind of “world model” that Bill rejects. But Bill immediately goes on to say:

BP: But those ideas may nevertheless be right.

RM: So what could this possibly mean. How could ideas that he just rejected be considered right? I think the answer is in this little paragraph here:

BP: I’m beginning to get an idea now about how to model perceptions, at
least at the lower levels. All we have to do is make a model of the
environment, just like that analog-computing trick for calculating
rates of change by using integrators, which turns out to embody
Newton’s laws of motion. This whole idea is still very new and I
don’t see very far along the path ahead, but I have a feeling that
what looked very difficult before may start getting a little less difficult.

RM: I think this is a description of how Bill sees the hierarchy of perception itself as the “world model” in PCT. In this case, Bill is describing how a perceptual function could develop to be a model of rates of change in variables. You start with a model of the environment – the external world – itself. In this case, the model is Newton’s laws of motion. Assuming that f = ma is something that is true in the environment then a perceptual function that perceives rate can be built as one that integrates force input:

input perceptual function perceptual signal

f----------------->| integral| --------------------> v

RM: The perceptual function senses force, f, and integrates sensed force over time producing a perceptual signal that is proportional to velocity, v.

RM: So the perceptual function becomes a model of as an aspect of the external world (per Newton’s model), the rate at which variables change over time.

RM: This is a more detailed description of what Bill meant when he said that the hierarchy of perception – the world as we experience it – IS the world model in PCT. We perceive the world in terms of intensities, sensations, configurations (objects), transitions (all of which seem like they are actually “out there”) and relationships (like “next to”, “below”), sequences (which see a little more subjective), programs, principles and system concepts (which seem completely subjective). But all these experiences are the way the brain models the external world. What we experience – the brightnesses, colors, objects (cars, people, etc), movements, relationships, sequences, etc – is our brains’ model of the external world

RM: Of course, since human brains are capable of perceiving the world in terms of high level perceptions like principles and program we (humans) have been able to develop very complex “world models”, like Newton’s laws, by doing science. These are the kind of “world models” – scientific models, which are very complex perceptions --that Ashby and the MCT types thought of as part of the control process itself. This was the kind of “world model” Bill rejected in the first paragraph of his post.

Best regards

Rick


Richard S. Marken

www.mindreadings.com
Author of Doing Research on Purpose.
Now available from Amazon or Barnes & Noble

[Martin Taylor 2015.05.01.14.41]

[From Rick Marken (2015.04.28.0900)]

The hierarchy of perceptual functions, I think.

Yes, but note that this involves reorganization and perception of

the lower-level output reference value (force) by a different
perceptual function. It’s the combination of force with acceleration
that leads to the new perceptual function.

I think it is _part of_ the world model, if you substitute

“perceptual function” for “perception”. The complete set of
perceptions is just your model of “the way the world happens to be
right now”. It’s not a model of “the way the world works”, which is
what is needed for imagination to be useful. As I said in my message
quoting Bill’s text, you have chosen to concepntrate on the
formation of perceptions, while I was initially focused on the
imagination connection itself. When I re-read Bill’s message as a
whole, I realized that we were both wrong to exclude the other’s
part of the story.

These are conscious models, and I do see them as perceptions. As

such, they are passive representations. But I think they are not
what Bill was getting at. However, if Bill really wasn’t aiming at a
functioning World Model (as I think he was), I still will argue that
there is a functioning world model embedded in the reorganized
structure of the entire hierarchy – all the perceptual functions,
all the reference input functions, all the interconnection weights,
and anything else I’ve forgotten.

Martin
···
          BP: I'm beginning to

get an idea now about how to model perceptions, at

                      least at

the lower levels. All we have to do is make a model of
the

                      environment,

just like that analog-computing trick for calculating

                      rates of

change by using integrators, which turns out to embody

                      Newton's

laws of motion. This whole idea is still very new and I

                      don't see

very far along the path ahead, but I have a feeling that

                      what

looked very difficult before may start getting a little
less difficult.

        RM: I think this is a description of how Bill sees the

hierarchy of perception itself as the “world model” in PCT.

        In this case, Bill is describing how a perceptual

function could develop to be a model of rates of change in
variables. You start with a model of the environment – the
external world – itself. In this case, the model is
Newton’s laws of motion. Assuming that f = ma is something
that is true in the environment then a perceptual function
that perceives rate can be built as one that integrates
force input:

input perceptual function perceptual signal

        f----------------->| integral|

--------------------> v

        RM: The perceptual function senses force, f, and

integrates sensed force over time producing a perceptual
signal that is proportional to velocity, v.

        RM: So the perceptual function becomes a model of as an

aspect of the external world (per Newton’s model), the rate
at which variables change over time.

        RM: This is a more detailed description of what Bill

meant when he said that the hierarchy of perception – the
world as we experience it – IS the world model in PCT.

        RM: Of course, since human brains are capable of

perceiving the world in terms of high level perceptions like
principles and program we (humans) have been able to develop
very complex “world models”, like Newton’s laws, by doing
science. These are the kind of “world models” – scientific
models, which are very complex perceptions --that Ashby and
the MCT types thought of as part of the control process
itself. This was the kind of “world model” Bill rejected in
the first paragraph of his post.