Tuesday, July 31, 2018

The subjective nature of meaning

Note: You may consider this to be deep background for my ongoing examination of Michael Gavin’s recent article on Empson, vector semantics, and Milton [1]. But it may also be understood independently of that discussion

It seems to me that the meaning of literary texts, as studied by literary critics, is ineluctably and irreducibly subjective. But we must be careful about that word “subjective”, for it has come to imply (often wild) variation from one person to another. While meaning may well vary from one person to another – the meanings literary critics discover through so-called close reading certainly vary among critics – that is not what interests me here. By subjective I mean simply that it is a phenomenon that exists in the mind of, you know, subjects. Whether or not meaning varies between subjects is a different matter. Color is subjective in this sense, though it is pretty constant across different people, color blindness providing the major exceptions.

(You might want to consult John Searle on subjectivity and objectivity in the ontological and epistemological senses. I am here asserting that meaning is ontologically subjective and leaving its epistemological status out of the conversation.)

Walter Freeman's neuroscience of meaning

The later Walter Freeman was interested in such things. I want to look at two paragraphs from a collection of his papers: Walter J. Freeman. Mesoscopic Brain Dynamics. London: Springer-Verlag Limited, 2000. 

These paragraphs are from the Prolog, which introduces the papers. One paragraph is fairly technical in its content while the following one is more accessible and can, in fact, be understood without having read the first one. So, I’m going to start with that second paragraph and then give you the first one. Moreover, I’m going to give you the first one twice. I insert some interpretive remarks into the repetition.

Here then is what Freeman has to say about meaning in the brain (pp. 9-10):
The point here is that brains do not process “information” in the commonly used sense of the word. They process meaning. When we scan a photograph or an abstract, we take in its import, not its number of pixels or bits. The regularities that we should seek and find in patterns of central neural activity have no immediate or direct relations to the patterns of sensory stimuli that induce the cortical activity but instead to the perceptions and goals of human and animal subjects. Far from being fed into our cortices in the way that we program and fill our computers, everything that we know and can remember has been constructed by the global self-organizing dynamics of activity within our brains.
That paragraph interprets this more technical and more specific one (p. 9):
... the bulbar AM patterns do not relate to the stimulus directly but instead to the meaning of the stimulus, as shown in several ways. The simplest way is to switch a reward between two odorants, so that the previously rewarded stimulus is no longer reinforced and vice versa. Both AM patterns change, though the two odorants do not. So also does the spatial pattern for the control segments in back- ground air. So also do all pre-existing AM patterns change when a new odorant is added to the repertoire. The AM patterns for all odorants that can be discriminated by a subject change whenever there is a change in the odorant environment. Furthermore, when rabbits are trained serially to odorants A, B, C, D, and then back to A, the original pattern does not recur, but a new one appears (Freeman and Schneider 1982; Freeman 1991a). This property is to be expected in a true associative memory, in which every new entry is related to all previous entries by learning, because the context and significance are subject to continual and unpredictable change.
Now I insert some interpretive remarks in italics:
... the bulbar AM patterns do not relate to the stimulus directly but instead to the meaning of the stimulus, as shown in several ways.

“Bulbar” refers to the olfactory bulb, a cortical structure involved with smell. “AM” is amplitude modulation. Freeman is recording electrical patterns from an array of electrodes touching the surface of the olfactory bulbs of “small laboratory animals”, Freeman’s phrase, generally rats or rabbits. Think of the AM patterns as signals.

The simplest way is to switch a reward between two odorants, so that the previously rewarded stimulus is no longer reinforced and vice versa. Both AM patterns change, though the two odorants do not. So also does the spatial pattern for the control segments in background air.

Note that the olfactory bulb is “upstream” from the olfactory receptors in the nasal cavity. Those receptors “relate to the stimulus directly”, while the bulbar AM patterns are suffused with meaning.

So also do all pre-existing AM patterns change when a new odorant is added to the repertoire. The AM patterns for all odorants that can be discriminated by a subject change whenever there is a change in the odorant environment.

That is to say, when a new odorant is learned a new pattern must be added to the existing array of patterns. But it is not merely ADDED TO array, leaving the existing one unchanged. All the preexisting patterns change.

Furthermore, when rabbits are trained serially to odorants A, B, C, D, and then back to A, the original pattern does not recur, but a new one appears (Freeman and Schneider 1982; Freeman 1991a). This property is to be expected in a true associative memory, in which every new entry is related to all previous entries by learning, because the context and significance are subject to continual and unpredictable change.

Digital computers do not use associative memory. Items in computer memory are accessed through their addresses. In associative memory there are no addresses independent of items in memory. Associative memory is said to be content addressed.
Note that Freeman thus has an objectively way of examining of phenomenon that is fundamentally subjective. But then students of color perception have been doing that for years.

Are all psychological phenomena thus (ontologically) subjective? How could they not be?

From Word Space to World Spirit?

What, you might as, does this have to do with Gavin’s article? Consider this passage (p. 647):
The playful exuberance of Empson’s method tries to capture something of words’ malleability and extensibility. Meanings aren’t discrete things, even though they inhere to words; instead they unfold over many dimensions of continuously scaled variation. Words have bodies and agency, Empson argues. Even a sort of personhood. They occupy an invisible lexical “thoughtspace” where they break apart and recombine to form superstructures, molding opinions and otherwise forging human experience.
It’s that phrase, “Meanings aren’t discrete things”. If learning a new odorant revises the whole array of learned identifications, those identifications can’t (quite be) discrete things, can they?

And what about the Word Space Gavin constructs? Where does it come from and what does it represent? Well, it’s based on a corpus of 18,351 documents from 1640 to 1699 (p. 662). Where did those documents come from? Yes, I know, they came from libraries. But before they got into libraries someone had to write them, each and every one. They came from the minds of a collectivity of writers.

Gavin’s Word Space models the distributional structure, the statistical semantics, of the documents in that corpus. The structure of any one document is a product of the writer’s mind; the writer’s mind structured the document. Hence, the document reflects the structure of that writer’s mind. If, in current parlance, the mind is what the brain does, then vector semantics of a document is a function of the state space of the writer’s brain. Does that mean that a Word Space model of a corpus is thus a model of the collective state space of the minds/brains that created the corpus? I know, it seems absurd, to go from a corpus of documents to a collective mind – a Hegelian World Spirit? But what else could it be?

Is that what we’re going, inferring from corpus semantics to collective minds?

What’s the world coming to?

* * * * *

I leave it as an exercise to the knowledgeable reader (I am not) to consider these matters in relation to Derrida’s concepts of diffĂ©rance and trace.

References

[1] Michael Gavin, Vector Semantics, William Empson, and the Study of Ambiguity, Critical Inquiry 44 (Summer 2018) 641-673: https://www.journals.uchicago.edu/doi/abs/10.1086/698174

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