[From Rick Marken (931026.0900)]
Martin Taylor (931025 15:05) --
Several participants in the discussion on contrast and the discussion on
category that followed it have suggested that category is something that
happens at every perceptual level, rather than representing in itself a level
This was not my suggestion. My point (and Bill's too, I think) was that
"categorization" is what perceptual functions do, in the sense that
the output of ANY perceptual function could be the result of many
possible inputs. Give this fact about the nature of perception, the
problem is to figure out what might be unique about the "categorization"
done by what we have been calling the "category" level of perception; in
other words, what TYPE of perception is a "category" perception. Maybe it's
not a separate type -- but, experientially, it seems like it is.
Bill P. has proposed that categorization is something done in
the perceptual input functions of logic level ECSs.
Again, this is not quite correct. "Categorization", as a many-to-one
mapping, is carried out by ALL perceptual functions (as noted above).
What I think Bill was saying is that what you, at one point, were calling
a "category" perception (ie. something that was in one class but NOT
another) was more like a "logical" type of perception.
I would like to propose an alternate view.
Category is defined not by a place in the hierarchy, but by a process.
That process is "contrast," and the contrast process can occur between
any two or more perceptions at any single level of the hierarchy.
Both association and contrast are seen as processes rather than perceptions.
The process of contrast is the suppression of perceptual signal PB as a
consequence of inputs to PIF-A that make PA go high; the process of
association is the enhancement of PB when PA goes high.
So a Mach band is a category perception?
The revisionist element I am proposing in this posting is that the PIFs in a
contrastive relationship, apart from their cross-linked inputs, can be of any
kind in the whole hierarchy, rather than being of one specific level.
But that doesn't seem to address the question of whether there are
"category" type perceptions and what they might be.
Bruce Nevin (Tue 931026 09:35:58 EDT) --
The phonemic contrasts of English partition the articulatory/acoustic
space available to all humans in a way that is different for English than
it is for French or Lakota.
How can contrasts (whatever those are) do anything -- let alone partition
a space? Are contrasts now control systems that perceive a particular
partitioning of articulatory/acoustic space, compare it to the intended
partitioning (the one for English, say, rather than French or Lakota)
and act to keep the perceived partitioning in the reference state? These
contrasts sure are amazing things -- I can see why linguists think that
they are so important.
I presume you mean that I hear many different acoustical variants
of the same word as being the same and each different word as being
discretely different because of "the way phonemic contrasts
exhaustively partition the available articulatory space". In other
words, these phonemic contrasts are what break a continuum of acoustical
signals into the discrete events that we call words. Is this right?
Then are "photemic" contrasts responsible for the fact that I
see different visual variants of the same object as being the same
and each different object as being discretly different? For example,
pick up a copy of "Mind Readings" or some lesser work; note that it has
a rectangular cover. Now rotate the book (slowly) in front of you. Note
that the book still has a rectangular cover. Yet the visual (retinal)
representation of the book is changing considerably as you rotate it.
A continuously varying visual object produces the same, discrete
perceptual result: "rectangle". The "rectangle" perception (resulting
from all those variants) can be easily contrasted with (seen as different
from) a "trapazoid" perception (if you had a trapazoidal book lying
around - or just cut out a trapazoid to see how different it looks from
the book --even when the book is casting what you know is a trapazoidal
image on your retina). This is a particularly interesting visual "contrast"
because, in many cases, the retinal shape of the rectangular object is
trapazoidal while the retinal shape of the trapazoidal object is often
As I've said before, there is nothing "special" about the perception of
words (speech) -- although I will apparently never be able to convince
a linguist of that fact. Linguists are familiar with many of the
perceptual phenomena involving language (speech). But I don't think
we're going to see much progress in this discussion of word perception
("contrasts") until we start dealing with actual models of speech