ontolog-forum
[Top] [All Lists]

Re: [ontolog-forum] brainwaves (WAS: to concept or not to concept, is th

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Mon, 17 Dec 2007 21:47:11 -0500
Message-id: <476734AF.8000106@xxxxxxxxxxx>
To illustrate the rate of progress in neuroscience, I'd like to quote
two discussions about perception:    (01)

  1. A summary of a paper that was published in the journal _Neuron_
     in January 2006.    (02)

  2. Three paragraphs about similar processes in Chapter 2 of my book
     _Conceptual Structures_ (published late 1983, copyright 1984).    (03)

If you compare the two, you may notice that there is nothing in the
2006 article that contradicts anything in my summary from 1983, which
cited psychological studies from 1960, 1967, 1970, and 1978.    (04)

John Sowa
______________________________________________________________________    (05)

Source: http://www.sciencedaily.com/releases/2006/01/060125082426.htm    (06)

"Vision doesn't happen in the eye," Connor said. "It happens at multiple 
processing stages in the brain. We study how objects are signaled or 
encoded by large populations of neurons at higher-level stages in the 
object-processing part of the brain."    (07)

The report, based on recordings of nerve cells in the visual cortex of 
macaque monkeys, reveals that neurons in the higher-level visual cortex 
at first respond to a visual stimulus "somewhat indiscriminately," 
signaling all the individual features within a shape to which they are 
sensitive. For instance, a particular neuron may respond to objects with 
either a concave fragment at the top or a convex fragment at the bottom. 
At this point, the neural signals are ambiguous; the brain doesn't know 
whether the concavity, the convexity or both are present.    (08)

Milliseconds later, however, neurons begin to react exclusively to 
combinations of shape fragments, rather than to individual fragments. In 
other words, the brain begins to put the pieces together to form larger 
sections, in the same way that an artisan might fasten discrete shards 
of stained glass to create a design.    (09)

"Humans do a rough categorization of objects very quickly," Connor said. 
"For instance, in just a tenth of a second, we can recognize whether 
something we see is an animal or not. Our results show that this 
immediate, rough impression probably depends on recognizing just one or 
more individual parts of what we see. Fine discriminations  such as 
recognizing individual faces  take longer to happen, and our study 
suggests that this delay depends upon emerging signals for combinations 
of shape fragments. In a sense, the brain has to construct an internal 
representation of an object from disparate pieces."    (010)

______________________________________________________________________    (011)

Source:  _Conceptual Structures: Information Processing in Mind and
    Machine_, by John F. Sowa, Addison-Wesley, Reading, MA, 1984.    (012)

 From Chapter 2 "Psychological Evidence" pp. 29-30:    (013)

Phonemes form syllables, syllables form words, and words form phrases 
and sentences. An important question is whether perception is a 
bottom-up process that first matches smaller units and combines them 
into larger ones or whether it is a top-down process that first matches 
large units and then fills in smaller details. Gestalt psychology is the 
classic example of a top-down theory. Figure 2.1 is a schematic face 
that illustrates the Gestalt phenomena. When reading the characters V 
and O in a line of text, a person normally interprets them as letters. 
But in the context of a face, they are interpreted as a nose and eyes. 
Even caricatures with just a few obvious features are easily recognized. 
When New York magazine printed a picture of an eggplant with pendulous 
jowls and an extra lobe jutting out for a nose, it was instantly 
recognized as Richard Nixon. Perceptual mechanisms find a schema that 
fits the overall stimulus before they analyze finer details.    (014)

In the context of a word, a reader does not normally see letters as 
separate units. Especially in speed reading, letters pass before the 
eyes at a faster rate than people can recognize them. Konorski (1967) 
found some patients with brain lesions who could read words, but they 
could not analyze words into letters. One patient "was able to read 
known words fairly well. However, when he was asked to spell them, he 
failed completely. He was also totally unable to read nonsensical words. 
When a word was presented to him in which one letter was changed, he 
usually did not notice the difference and read the word as if it were 
written correctly. For example, seeing the word okilary he read it as 
okulary (in Polish, spectacles) not being able to discover that one 
letter was changed. When more letters were changed, he failed completely 
to read the word" (p. 121). Konorski concluded that these patients saw 
the words as unitary percepts, not as composite structures.    (015)

Studies of the speed of perception also support top-down theories. When 
a picture of a man is briefly flashed on a screen, a person first 
identifies the general form and later notices the details of face, 
hands, shirt, and tie. Bever (1970) found that people could recognize 
spoken syllables faster than they could recognize single phonemes: when 
subjects were told to listen for a word starting with the syllable bo-, 
they responded 70 milliseconds faster than when they were listening for 
a word beginning with the phoneme /b/. Furthermore, people can recognize 
sentences faster than single words: subjects responded consistently 
faster when they were listening for the sentence "Boys like girls" than 
when they were listening for the first sentence beginning with the word 
boys. For recognizing large vocabularies by computer, White (1978) 
proposed a top-down method of matching templates for complete words 
instead of first trying to recognize individual phonemes. He estimated 
that the processing time would be reduced by a factor of 10 to 100.    (016)

Multiple levels of percepts can help a person deal with novelty. A 
common phrase like United States may be matched by a single percept, but 
a less common phrase like United Fruit may require two separate 
percepts. For an unfamiliar word like antidisestablishmentarianism, 
perception may carry the analysis down to single syllables or groups of 
syllables like anti-. And for a rare syllable like Omsk, it may go down 
to the level of individual phonemes. The mechanisms for handling 
percepts are innate, but the particular stock of percepts must be 
learned. Some percepts are learned by rote memory, but the most 
productive source is the construction of compound percepts from smaller 
ones. Even though adults read a complete word or phrase as one unit, 
children learn to build up words from combinations of letters.    (017)

Some evidence favors a top-down approach, and other evidence favors a 
bottom-up approach. In their work on stabilized images, Pritchard et al. 
(1960) found evidence both for the stability of the whole, as Gestalt 
theory maintains, and for the existence of parts for building the whole. 
They concluded that both approaches "are valid and complement one 
another." This psychological conclusion has also emerged as a basic 
principle of AI: top-down reasoning is a goal-directed process that 
imposes a tightly controlled organization; bottom-up reasoning is a 
data-directed or stimulus-directed process that leads to more diffuse 
chains of associations. The two approaches may be combined in 
bidirectional reasoning, which is originally triggered by some stimulus 
in the data, but which then invokes a high-level goal that controls the 
rest of the process. Some problems are more naturally handled by one 
approach or the other, but the combination of the two is especially 
powerful.    (018)


_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/  
Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/  
Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/ 
To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx    (019)

<Prev in Thread] Current Thread [Next in Thread>