Notes on computational linguistics.pdf - UCLA Department of ...

Stabler - Lx 185/209 2003
16.5 Inference
16.5.1 Reasoning is shallow
It is often pointed out that commonsense reasoning is “robust” and tends to be shallow and in need of support
from multiple sources, while scientific and logical inference is “delicate” and relies on long chains of reasoning
with very few points of support. Minsky (1988, pp193,189) puts the matter this way:
That theory is worthless. It isn’t even wrong! – Wolfgang Pauli
As scientists we like to make our theories as delicate and fragile as possible. We like to arrange
things so that if the slightest thing goes wrong, everything will collapse at once!…
Here’s one way to contrast logical reasoning and ordinary thinking. Both build chainlike connections
between ideas…
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Commonsense Reasoning
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Mathematical Logic
Logic demands just one support for every link, a single, flawless deduction. Common sense asks,
at every step, if all of what we’ve found so far is in accord with everyday experience. No sensible
person ever trusts a long, thin chain of reasoning. In real life, when we listen to an argument, we
do not merely check each separate step; we look to see if what has been described so far seems
plausible. We look for other evidence beyond the reasons in that argument.
Of course, shallow thinking can often be wrong too! In fact, it seems that in language understanding, there are
many cases where we seem to make superficial assumptions even when we know they are false. For example,
Kamp (1984, p39) tells the following story which I think is now out of date.
We are much assisted in our making of such guesses [about the referents of pronouns] by the spectrum
of our social prejudices. Sometimes, however, these may lead us astray, and embarassingly so,
as in the following riddle which advocates of Women’s Lib have on occasion used to expose members
of the chauvanistic rearguard: In a head-on collision both father and son are critically wounded.
They are rushed into a hospital where the chief surgeon performs an emergency operation on the
son. But it is too late and the boy dies on the operating table. When an assistant asks the surgeon,
‘Could you have a look at the other victim?’, the surgeon replies ‘I could not bear it. I have already
lost my son.’ Someone who has the built-in conception that the chief surgeons are men will find it
substantially more difficult to make sense of this story than those who hold no such view.
What is interesting in the present context is that this story was puzzling in 1984 even for people who knew
perfectly well that many surgeons were women, because the stereotypical surgeon was still a man. That is,
superficial reasoning can relies on stereotypes that are false, and to be clear to your audience it is important to
state things in a way that anticipates and avoids confusions that may be caused by them. The role of superficial
assumptions has been explored in studies of conceptual “prototypes” and human language processing (Lynch,
Coley, and Medin, 2000; Dahlgren, 1988; Smith and Medin, 1981; Rosch, 1978)
As mentioned in §16.5.1, it could be that the reasoning is actually not as unbounded as it seems, because
it must be shallow. For example, It is historical and literary knowledge that Shakespeare was a great poet, but
the knowledge of the many common Shakespearean word sequences is linguistic and perfectly familiar to most
speakers. If we start thinking of familiar phrasing as a linguistic matter, this could actually take us quite far
into what would have been regarded as world knowledge. 54
54 This kind of linguistic knowledge is often tapped by cluse for crossword puzzles. Although solving crossword puzzles from clues
involves many domains of human knowledge, it draws particularly on how that knowledge is conventionally represented in language,
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