paradox of control?

CSGnet Archive CSG1998
21

[From Bill Powers (980309.0822 MST)]

Bruce Nevin (980308.1807)--]

Sounds like the higher up in the hierarchy you go the more the perceptual
signal is a construct projected onto the environment. There are sensors for
acid, salt, perhaps oil, I don't know; there is no direct sensor for the
taste of lemon. The suggestion seems to be that signals directly from
sensors (all intensity perceptions?) are closest to reality.

In my conception of the hierarchy, all levels are equally considered as
constructs relative to the next lower level. Even a sensory signal from a
single receptor is a construct, because it is a single signal representing
multiple environmental variables. The multiplicity comes about because more
than one kind of physical stimulus, or more than one location of a given
kind of stimulus, produces exactly the same perceptual signal from a given
receptor. Beginning at the very lowest level, perception is a
simplification of the physical world.

What we can hope for, and argue for, is that perceptions at any level
correspond, however loosely, to large-scale and time-spanning properties of
the real world outside us. We can afford to be skeptical about the
correspondence of perception to reality; the fact that we can control our
perceptions by emitting actions into a largely unknown world shows that
there are regularities out there, so we need not be concerned with solipsism.

Sensors are also input functions. Low-level perceptions are also
constructs. But being as close as we can get to the physical environment we
call these perceptions "directly perceived reality". Am I with you?

Yes, but I don't think we have to be concerned with getting "closer to
reality." There's no way we will ever know, for sure. We can only judge the
aptness of our models by seeing how much effort it takes to believe in them
and support them against criticism, and how much adjusting it takes to keep
them predicting correctly. The best possible model would never need any
adjustments.

One direction is to try to attain an objective point of view. I don't hear
you suggesting that.

No. I don't believe there is any objective point of view. Whatever you mean
by that. The best we can do is construct models for public inspection, and
reason by agreed-upon procedures, so at least we can test our models for
consistency from one observer's world to another's.

Aother direction is to try to attain the point of
view of the control system being modelled. Same problem of projecting one's
own perceptions, but probably more attainable.

That's pretty much the basic task in modeling, isn't it? My general
assumption is that if I can build a model that explains my own behavior and
perceptions (which I always perceive from the viewpoint of the control
system, of course), then it will probably work for other people, too. This
is most likely to be true at the lower levels of control, where we are all
using close to the same equipment. But even at the higher levels, the
assumption is useful because _failures_ to predict correctly reveal the
dimensions in which we can be different from others, and also help to
dispel the illusion that what we experience is reality itself.

Best,

Bill P.

22

[From Bill Powers (980309.0906 MST)]

Bruce Abbott (980309.0900 EST)--

In most (all?) cases perception is a construct from the start. The retina
contains four kinds of photoreceptor, three of which together provide the
basis of color vision. These three are "tuned" to different frequency bands
of the electromagnetic spectrum; their peaks overlap somewhat. What we call
yellow usually begins as a particular frequency of light, one that activates
the two lowest-frequency photoreceptors about equally well.

I agree in general with what you're saying, but disagree with a few
details. The experience of yellow, for example, would very seldom begin
with a single-frequency light stimulus. If you use a specroscope to look
at any natural object that we see as yellow, there is essentially no chance
that we would find all the light energy concentrated at a single wavelength.

The spectral bands of the eye overlap not slightly, but mostly, at least
for the red-green bands. Edwin Land showed that the most important
distinction in color vision is between long and short wavelengths; the same
object can appear to be different colors depending on the colors of other
objects in the same visual field -- yet a given object can be seen as the
same color even though it is illuminated by light that does not contain
that color at all, or that changes the received spectrum of light energy to
match exactly the spectrum of a different color seen under normal lighting
conditions. There is, in fact, no simple correspondence of perceived color
to the spectrum of incoming light.

Equal
co-activation of these receptors and the near-absence of activity in the
highest-frequency receptor ultimately give rise to the perception we label
as yellow.

I don't think this view can be supported any more. There are too many
counterexamples, particularly those provided by Land.

In this example "yellow" is "really there" (in the sense of there being
present a particular frequency of light which we label as yellow). However,
shining "red" and "green" light (particular light frequencies) on the same
part of the retina will also produce equal co-activation of the two
lowest-frequency receptors and will also produce the perception of yellow.
In this case the yellow (as a frequency of electromagnetic wave) is not
present at all. This is the method used in color TV to produce all the
colors of perception using only the three "primary colors."

Isn't it much simpler just to say that yellow is the output of a particular
perceptual input function, without trying to claim that it represents
something real in the environment? Is there some reason NOT to say it that
way?

Similarly, variations in temperature seem to be conveyed as the intensity
signals of a single sense, but in fact the perception of temperature arises
from the co-activation of two, more specific, receptors in the skin. One
receptor becomes more active as skin temperature increases above some value
(the "warm" receptor). The other has an inverted U-function, becoming more
active as skin temperature falls below some value _or_ as the temperature
reaches an upper extreme. This latter receptor is labeled the "cold"
receptor and conveys the impression of "burning" hot when co-active with the
warm receptor. (Aside: I have omitted sensory adaptation effects in this
description, which complicate the picture somewhat.)

Fine, and that's interesting (I didn't know about the inverted-U-shaped
"cold" signal). But doesn't all this argue against the idea that there is a
simple correspondence between sensation perceptions and physical reality?

Best,

Bill P.

23

[From Bruce Gregory (980309.1208 EST)]

Bill Powers (980309.0822 MST)

What we can hope for, and argue for, is that perceptions at any level
correspond, however loosely, to large-scale and time-spanning properties of
the real world outside us. We can afford to be skeptical about the
correspondence of perception to reality; the fact that we can control our
perceptions by emitting actions into a largely unknown world shows that
there are regularities out there, so we need not be concerned with solipsism.

You did that just to make me feel better, right? I'm sure you
meant "by acting on a largely unknown world".

I don't believe there is any objective point of view. Whatever

you mean

by that. The best we can do is construct models for public inspection, and
reason by agreed-upon procedures, so at least we can test our models for
consistency from one observer's world to another's.

Just so.

Bruce

24

[From Bruce Gregory (980309.1212 EST)]

Bill Powers (980309.0906 MST)]

The spectral bands of the eye overlap not slightly, but mostly, at least
for the red-green bands. Edwin Land showed that the most important
distinction in color vision is between long and short wavelengths; the same
object can appear to be different colors depending on the colors of other
objects in the same visual field -- yet a given object can be seen as the
same color even though it is illuminated by light that does not contain
that color at all, or that changes the received spectrum of light energy to
match exactly the spectrum of a different color seen under normal lighting
conditions. There is, in fact, no simple correspondence of perceived color
to the spectrum of incoming light.

There is a very nice discussion of this in the first
chapter of Oliver Sack's book _An Anthropologist on Mars_.

Bruce