Challenges in Natural Language Processing:

Challenges in Natural Language Processing:

A Taster of Philosophical Issues Arising from an AI Project Lecture for Philosophy of Cognitive Science 2011/2012 Semester 2 John Barnden (Prof of AI) School of Computer Science University of Birmingham, UK Plan of Lecture Beginning (well defined) Middle (variable)

End (poorly defined) because I want questions and discussion THEME: Ill give you a taster of some of the philosophical issues that have arisen in my research or are related to it. Some Questions to You (QTYs) At what address did Sherlock Holmes live?

Is London the city in which the SH stories are set? Has SH died yet? How many warts did he have? How many legs does a unicorn have?

What is a number? Where do all the numbers, sets, computer programs, ... live? What does/might Everyone is a moon mean? What does/might The Governments plan for the NHS is really fantastic mean?

Perhaps theres something wrong with some of these questions? (QTY4L8R) ... Beginning ... My main research interest: AI methods for understanding figurative language and the interdisciplinary (incl. philosophical, psychological, linguistic) ramifications and the practical applications Figurative language = metaphor, irony, hyperbole (exaggeration), etc. Subsidiary interests:

consciousness, emotion, ... creativity (of any sort, incl. artistic and scientific) (theres a growing Computational Creativity subarea of AI) nature of representation Still Beginning Some of the importance of "philosophical" issues to CS and AI: Theyre often about deep conceptual matters that can affect the whole enterprise of developing a computational approach to some problem area. Proper philosophical consideration can help you avoid getting into overly abstract, unrealistic approaches. End of the Beginning: Issue Morsels

FICTIONALISM everyone entertains lunatic fantasies all the time? numbers, programs etc. ain't what you thought they were in fact they aren't anything? METAPHOR IN THOUGHT mind as metaphorical mush BOUNDARIES OF MEANING meaning as a holistic gas

hidden meanings rule OK Practical Importance of Fig Lang Common in language, so ultimately needs to be dealt with in AI language systems of many different sorts Becoming important in Sentiment Analysis systems, for extracting evaluative opinions and emotions from product reviews, customer complaints, etc. Becoming important in the security area, because metaphor etc. can be culture-specific Metaphor is important in psychotherapy Conversation about practical matters (e.g. travel) involves metaphor, etc. A Fictionalist Approach to Metaphor in the ATT-Meta theoretical approach to metaphor understanding, with accompanying implemented system for handling the reasoning involved.

Uses a fictionalist or pretence-based approach, whereby the typically absurd literal meaning of the metaphor is pretended to be true, and consequences about the real world extracted by various means. But, as with many other approaches, if a metaphorical word or phrase is conventional/familiar enough then its meaning may be directly accessible from it. Possible examples: milestone, attack, dead, back of Xs mind The most interesting cases are the remainder. I claim many/most of these are handled by pretence. Examples of Metaphor Johns exam marking overflowed into the weekend

The idea was buried in the far reaches of Katys mind I dont think strings are attached. If there are any theyre made of nylon [QTY] The managers were getting cricks in their necks from talking to [lots of different people] I nurtured those doubts as if they were tiny, sickly kittens. [Nick Hornby] Everyone is a moon, and has a dark side which he never shows to anybody. [Mark Twain] (QTY: notice something wrong with that?) Im going to give you a taster of philosophical issues. ..... Issue Morsels Some Terminology A metaphor has a source side and a target side. In Johns exam marking overflowed into the weekend, the target side is to do with Johns marking in itself the source side is to do with physical liquids, their movements, physical

containers, etc. I talk of source-side and target-side subject matter, situations, scenarios, ... The two sides are conceptual, not primarily parts of the wording. The Fictionalist Process The idea was buried in the outback of Katys mind The understander (as well as the speaker) momentarily pretends that Katys mind is literally a physical terrain that has an outback and that the idea is literally physically buried in the outback. Physical burying, especially in relatively inaccessible locations such as an

outback, implies (by default): a high degree of current lack of physical manipulability and physical hiddenness and a high degree of difficulty for attempts to physically manipulate it. So the idea in question is inferred to be (to a high degree) physically hidden to, currently physically unmanipulable by, and difficult to physically manipulate by Katys conscious self. J = the idea Reality (incl. target-side) J is buried in ... J is a phys object Ks mind is a phys terrain

inference K is not aware of J J physly hidden to Ks c. self J not physly manipulable by Ks c. self J would only be manipulable with difficulty by Ks c. self K cannot mentally use J K would find it difficult to mentally use J pull-out Examples of Known Mappings

For the metaphorical view of IDEAS AS PHYSICAL OBJECTS, we might have: X mentally using an idea Xs conscious self physically manipulating the physical object that the idea is pretended to be. X being [consciously] aware of an idea Xs conscious self seeing the physical object that the idea is pretended to be. Notes on Pretence The word pretence has a number of different meanings, and people have different intuitions about what it covers. The relevant notion in the ATT-Meta approach does not imply any sort of deception or insincerity.

Rather it is honest pretence, usually but not necessarily as part of a communication with someone else. Some cases: Fiction in general (NB: pretending that as opposed to pretending to) Drama Childrens pretend play Fancy-dress balls (adults pretend play!) Counterfactual statements: If I were the head of the Football Association Id set up a new world governing body for football. Fiction[alism]: Other Issues In narrative fiction: what sense can we make of fictional entities? where does/did Sherlock Holmes live? how many warts does/did he have? does he exist even when no-one in the whole wide world is reading or thinking about him? What about if also all books etc. about him have been destroyed?

if someone else wrote an SH story/filmwould it be about the same entity? Fictionalism: Other, contd Fictionalism about what we normally think of as real: e.g. about numbers (QTYs) : what is a number? do they exist? where are they? would they exist if there were no people? Arithmetic is like a Sherlock Holmes story? The connections are deductively certain, as opposed to SH fiction, so it's easier to agree on the rules. Fictionalism: Arithmetic, contd

But there is dispute about the tenets of the underlying set theory e.g. whether a set can belong to itself; questions about the nature of infinite sets. Sets themselves are fictional? What about computer programs? (QTY) Metaphor in Thought A common modern view: metaphor is not fundamentally a matter of communication / external expression, but of the way we think about many aspects of life (where the thinking is not itself a matter of internal English or whatever). Metaphor is in many different forms of communication,

expression and other activity: Gesture Diagrams (cf. arrows, blobs, etc. in my diagram above: QTY4L8R) Pictorial representation Dance Music Sport, Games But what does M4-in-T amount to?? A weak analogy-based view: we can in principle think about, say, love without metaphor,

but have analogies in our minds with separate knowledge structures about journeys, businesses, etc. 2 variants: the knowledge structures have separate origin, but we established an analogy (in our lifetimes or during species development) the structure of (some of) our knowledge about love comes from knowledge about journeys, etc. A very strong view: our knowledge structures about love actually intrinsically involve our knowledge structures about journeys, etc. Metaphor in Thought, contd Some possibly relevant psychological experiments show theres some sort of embodiment of metaphor, even metaphor that is

highly conventional. E.g., bodily movement can affect our inferences about time. We talk metaphorically about time as if it were a spatial dimension. On one metaphorical view, were moving along a time line. On another, future times and events are moving towards us. They give exactly opposite meanings for e.g. Lets move the meeting forwards. Engaging in or even imagining forwards movement has been shown to bias people towards interpreting that phrase to mean: make it later. QTY4L8R: what does this show about metaphor in thought, if anything? Thats as far as I got in the lecture The Restrained-Parallelism Tendency

in Metaphor according to ATT-Meta There is less parallelism needed in metaphor than often implied/assumed The idea was buried in the outback of Katys mind. My claim: buried and outback are merely mental tools towards the target-side meaning ... via existing mappings such as physical operation mental usage. There is no need to, and it could be difficult to, discover mappings for the map-transcending notions introduced by buried and outback. The familiar, existing parallelism (analogy), e.g. between mental matters and physical matters, need not (and often cannot) be extended. Restrained Parallelism, contd. He was spinning his wheels: his wheels dont need a parallel.

I dont think strings are attached. If there are any theyre made of nylon: made-of-nylon, or nylon and made-of separately, dont need parallels. The managers were getting cricks in their necks from talking to [lots of different people]: cricks and their necks dont (normally) need parallels. (Grammatical) Boundaries of Meaning Everyone is a moon, and has a dark side which he never shows to anybody. [Mark Twain] A possible variant (QTY) : Everyone is a moon. Everyone has a dark side which he never shows to anybody.

The clause/sentence Everyone is a moon does not need to be given its own target-side meaning. Rather, it conspires with the other clause/sentence to convey an overall fictional/pretence scenario. Indeed, the moon clause/sentence really just consolidates the info from the other segment. [Or would do if it were astronomically accurate!] (Grammatical) Boundaries, contd. This and many other examples suggest that: Meaning from discourse should not be thought to be tied to (bits of) sentences in particular: rather it can arise in a much more holistic way from arbitrary stretches of discourse, involving various sentences and bits of sentences. Viewing sentences as the central meaning-bearers is just an artefact of traditions in language study over the centuries.

Speech units =/= sentences, particularly. And meaning in speech is partly carried by intonation, gesture, etc. which dont necessarily respect sentence boundaries. Boundaries of Meaning: Different Types of It A highly contentious distinction: What is [directly] said [WiS] versus What is implicated [implicatures] Some people view metaphorical meanings as implicatures from WiS, at least when not conventional. More standard example: Saying Youre squashing my arm to mean Get the hell over to the other side of the bed. Very difficult in general to draw a clear distinction.

WiS vs Implicatures: Irony Case The Governments plan for the NHS is really fantastic. WiS = the literal meaning of that. Implicatures: Ironic content: The plan is bad. Ironic attitude: [e.g.] Its pretty idiotic to think its a good plan. Syntactically Embedded Irony S: If Alice is such a genius well be sure to lose in the quiz. NB: Only the antecedent is ironic.

Appropriate in various types of context: People have already been talking ironically about stupid Alice. [S continues existing negativity and irony.] People have been talking non-ironically about stupid Alice. [S continues existing negativity but introduces irony.] People have been sincerely claiming Alice is clever but the speaker of S isnt convinced. [S introduces negativity and irony.] Embedded Irony, contd. Raises issues for the WiS/Implicature distinction, and for the role of different implicatures.

Sentence Ss consequent clause is asserted to hold if the ironic content of the antecedent (Alice is stupid) holds: the literal content and the attitude implicature are both irrelevant. Need a way of explaining what the fate is of different implicatures of different sorts of statement in different sorts of embedding, and of working out fairly clearly what some of the specific implicatures are. And is the natural interpretation of S itself a WiS or an implicature? If the former, a WiS can depend on an implicature, upsetting standard theories of WiS.

If the latter, the WiS is strangely irrelevant: do we work it out at all? Conclusion (= Start of Next 1000 Years of Philosophy) FICTIONALISM Metaphor: everyone entertains lunatic fantasies (fictions)? (More) Fictionalism: numbers, programs etc. ain't what you thought they were. In fact they aren't anything? METAPHOR IN THOUGHT mind as metaphorical mush: some of our thought may be intrinsically metaphorical (and thats a good thing I like mush!).

BOUNDARIES OF MEANING meaning as a holistic gas/mush, not linked to fixed grammatical boundaries. hidden meanings rule OK: implicatures are often crucial. A Few References Barnden, J.A. (2007). Metaphor, semantic preferences and context-sensitivity. In K. Ahmad, C. Brewster and M. Stevenson (Eds), Words and Intelligence II: Essays in Honor of Yorick Wilks, pp.39-62. Berlin: Springer.

Barnden, J.A. (2008). Metaphor and artificial intelligence: Why they matter to each other. In R.W. Gibbs, Jr. (Ed.), The Cambridge Handbook of Metaphor and Thought, pp.311-338. Cambridge, U.K.: Cambridge University Press. Many other chapters in that Handbook. Casasanto, D. & Boroditsky, L. (2007). Time in the mind: Using space to think about time. Cognition, 106, pp.579-593. Currie, G.~(2006). Why irony is pretence. In S. Nichols (Ed.), The Architecture of the

Imagination, pp.111-133. Oxford: OUP. Fogelin, R.J. (2011). Figuratively speaking. Revised ed. New York, Oxford: Oxford University Press. (The main library has the 1988 edition, which is also fine.) John, E. & Lopes, D.M. (2004). Philosophy of Literature: Contemporary and Classic Readings. Blackwell. Despite the title, many of the chapters are significant beyond literature.

((I can provide more references on specific topics.)) Do the cat-flaps of time allow the aardvarks of questioning to snort up the maggots of incoherence? EXTRA SLIDES Honest Pretence Any sort of imagining (conscious or not) of a situation you think is unreal, and is presented in that spirit to yourself or others, is honest pretendingthat.

This isnt to say that its immediately obvious to another person that youre engaging in pretence, or that there are clear signals that pretence is going on. The Fictionalist Process: a detail I claim that mind-as-physical-region metaphors involve the ancillary assumption that the persons conscious self is pretended to be a person in a central part of the region. The ATT-Meta Approach, contd So what?? We now need to have some way of pulling out some version of some information in the pretended situation

to become information about the target situation (Katys actual state of mind). What Im aiming for in the Katy example is that by pull-outs the understander derives the propositions that (to a high degree) Katy is not aware of the idea, cannot currently mentally use the idea, and would find it difficult to mentally use it. The ATT-Meta Approach, contd For purposes of pull-out in general, there are three logical possibilities: Some information may be able to be copied over as-is (no transformation) We have known transformations of some types of information We work out new transformations of some information from scratch.

All three are veteran actors on the stage of metaphor theory (pretence-based or not). New-transformation has been postponed in the ATT-Meta project: can be important, but only rarely so in practice (even in literary metaphor cf. [Lakoff & Turner & 1989]) No-transformation and known-transformation are used in ATT-Meta. Known-transformation: roughly following the idea of mappings in Conceptual Metaphor theory [Lakoff & Johnson; Grady variant] and in research on analogy. The ATT-Meta Approach, contd No-transformation case: done by View-Neutral Mapping Adjuncts (VNMAs). They lead to copying of certain types of commonly-occurring information. Example: IF

pretend action P corresponds to target-situation action Q AND IF pretend agent X corresponds to target-situation agent Y, THEN ability of X to do P corresponds to ability of Y to do Q (by default) They are parasitic on existing postulated pretence/target correspondences (mappings). But they are independent of where those correspondences come from, and notably from what specific metaphorical views (such as IDEAS AS PHYSICAL OBJECTS) are in operation.

VNMAs provide great economy: e.g. No need to have an ability version of the view-specific physical-manipulation/mental-usage mapping, or ability version of other mappings. Info Handled by some VNMAs ability, ease, causation, enablement, etc. degrees (intensities) modalities (incl. if ... would) uncertainty event shape, temporal relationships sets, qualitative set sizes emotional and mental states, value judgments Other No-Transformation Cases

Any type of info could, in the right specific circumstances, correspond without transformation. E.g., one might metaphorically cast a person as a horse because of the shape of their nose and their speed of running. The point is that only certain types of information can be assumed to correspond when theres no specific counter-evidence. A person/horse metaphor would not allow one to assume that the person eats raw oats, etc., just because theres no evidence that the person does not eat those things. One might of course wonder whether the person eats those things.

And in the right context, part of the point could be that the person does eat those things. So: VNMA-style info: can copy over Other Info: unless theres a reason against cannot copy over unless theres a specific reason for Mappings as working on Pretence Rather than Domains of Knowledge

In other approaches, mappings are thought to be between a source domain and a target domain (or other similar constructs), where domains are subdivisions of our knowledge of the world. This rests on notions of domain (etc.) that I dont believe. I cast mappings as just relating two different things (no matter what domains these things might involve), where one thing is assumed to be in a pretended scenario and the other in a target-side scenario. [related to Waltons principles of generation] I dont assume any precise delineations of subject-matter.

The subject-matter in the pretence is typically from the source side of the metaphor, but can include real (non-pretend) information, and any subject matter that is relevantly connected to the source-side subject matter. Pretence Alongside another Unreality J is a phys object Ks mind is a phys terrain J is buried in ... Non-real target-side K is not aware of J

J physly hidden to Ks c. self J not physly manipulable by Ks c. self J would only be manipulable with difficulty by Ks c. self K cannot mentally use J K would find it difficult to mentally use J Multiple Pretences Consider a play within a play, or a story within a story. This involves nested fictions, i.e. nested pretences. Nesting of pretences/fictions in the language area also has been discussed in heterogeneous cases, as when there is an ironical statement by a character in a fictional work [Currie 2006].

But also useful for serial compounding (chaining) of metaphor: X viewed as Y and Y viewed as Z E.g.: This worry was a corrosive chemical that was nibbling at her selfesteem. [closely adapted from an example in a Sylvia Plath diary] The worry (X) is viewed as a chemical (Y); the chemical (Y) is viewed as an animal (Z). the second view is typically expressed as acids, etc. eating [into] things. [Also, her self-esteem is viewed as a nibblable physical object.] The worry-chemical-ANIMAL is nibbling at her self-esteem-object The worry-chemical-ANIMAL is slowly eating her self-esteem-object

The worry-CHEMICAL is slowly physicallydamaging her selfesteem-object The WORRY is slowly affecting her self-esteem negatively Multiple Pretences, contd Multiple (but non-nested) pretences also useful for Parallel compounding of metaphor: X

is viewed as both Y and Z where Y is not itself (on this occasion) viewed as Z, and Y and Z are difficult to combine within one pretence. Marriage is both a business and a journey. There are sometimes complex combinations of parallel and serial compounding.

BUSINESS info MARRIAGE info JOURNEY info Restrained Parallelism contd Adapted from a novel [Nick Hornby, High Fidelity, 1995]: I tried not to run down Phil too much. But it became unavoidable, when Jackie expressed doubts about him. I nurtured those doubts as if they were tiny, sickly kittens. Eventually they became disturbing, long-lasting grievances. These cats had their own cat-flaps. This allowed them to wander in and out of our conversation at will.

The cat-flaps and at-willness dont themselves need target parallels. They just emphasize, via the pretence scenario, the non-deliberateness (on the part of the conversants) with which the grievances occurred in the conversations. Even the cat-ness in the pretence scenario has no target-side parallel. It just provides a conceptual framework for describing a process in which doubts become strong grievances. Grain-Size of Metaphorical Interpretation These cats had their own cat-flaps. This sentence does not (need to) have its own target-side

meaning. The appropriate level for metaphorical interpretation is sometimes a multi-sentence chunk of discourse (or a chunk consisting of multiple metaphorical clauses). I.e.: Individual metaphorical units within the chunk are not all given separate interpretations. Rather, the whole chunk describes a pretence scenario, and its from this that the target-side info is derived in a somewhat holistic way. No necessary sentence-by-sentence or clause-by-clause parallelism. Shifting into Reverse: Metaphorization Literal elements of a discourse may best be translated into terms of the source side to engage with the pretence scenario: metaphorization of the literal reverse of normal process assumed in metaphor understanding!

It is intuitively natural to build in one's mind a scenario of the sickly kittens becoming healthy kittens or adult cats. But where is this biological recovery and growth implied? Answer: in the literal sentence Eventually they became disturbing, long-lasting grievances. Metaphorization of the info from this sentence is desirable, in order to enrich and be integrated with the pretence scenario.

And if we claimed that the integration should instead happen on the target side, then thered be more pressure to try to convert all sentences including These cats had their own cat-flaps into target terms with great difficulty. Metaphorization, contd. Actually, Hornbys original wording was not Eventually they became disturbing, long-lasting grievances but Eventually they became sturdy, healthy grievances. But still, desirable to convert grievances into cats

and convert the abstract became into biological growth and recovery. Dont want just to get target-side info from the sentence by itself. Conclusions, 1 Restrained parallelism: Metaphorical wording often plays the important role of guiding inference within the pretence whose conclusions are mapped, rather than describing pretence elements that should, or even could, be mapped. So the interpretation job is Simpler than you may have thought (less mapping-construction) but also More Quirky than you may have thought (the wording has less to do with the target side, and is more unconstrained).

Conclusions, 2 A special corollary, with Yet More Quirk : The grain-size of truth attribution to language (even when literal?) is not the sentence in general. Sentences (etc.) collaborate with each other to describe pretence scenarios without necessarily having their own individual target-side meanings. [cf/cp. Donald Davidson] Sentence-by-sentence truth is just a convenient heuristic fiction [sic!] that works well enough much of the time. Quirk Alert:

Depending on context, it can make sense to metaphorize literally-presented information in discourse.

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