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On lexical ambiguity

On lexical ambiguity. Ágoston Tóth, PhD University of Debrecen tagoston @delfin.unideb.hu Ruzomberok 24 June, 2009. Sponsored by OTKA research grant K 72983. Homonymy, p olysemy. Homonymy Bring money from the bank . bank 1 : [ financial institution ]; bank 2 : [ riverbank ]

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On lexical ambiguity

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  1. On lexical ambiguity Ágoston Tóth, PhD University of Debrecen tagoston@delfin.unideb.hu Ruzomberok 24 June, 2009 Sponsored by OTKA research grant K 72983

  2. Homonymy, polysemy Homonymy Bring money from the bank. bank1: [financial institution]; bank2: [riverbank] Polysemy bulb: [the root of a plant] ~ [an electric lamp] Fuzzy boundary! Workaround: maximize homonymy or maximize polysemy (Lyons 1977). NLP lexicons (incl. WordNet): maximize homonymy Semcor corpus “polysemy” factor: 6.6 senses/word on avg. (Mihalcea and Moldovan 2001)

  3. Cruse’s lexical semantics Test for antagonism: we can focus on one reading at a time Bring money from the bank. She was wearing a light coat. (Cruse 2000) Other tests for the presence of discrete readings. Relatedness of senses: continuous phenomenon

  4. A tacitpremise If a lexical item causes ambiguity, it can be disambiguated, i.e. we can pick out a “right meaning” for each lexical item in a sentence.

  5. Plausibility of word sense disambiguation (WSD) Word Sense Disambiguation The selection of the “right” meaning for each lexical item in a sentence. Senseval-3(cf. Snyder & Palmer 2004) 26 competing systems. Accuracy: up to 65% (best system, best case) Always-select-the-most-frequent-sense (MFS) baseline: 61% Human inter-annotator agreement: 72%

  6. Plausibility of word sense disambiguation (WSD) Conclusion of Semeval-7 (all-words disambiguation task): “after decades of research in the field it is still unclear whether WSD can provide relevant contribution to real-world applications” (Navigli, Litkowsky & Hargraves 2007:34)

  7. Other linguistic fields with correlating findings Lexicographical practice “lumping is considering two slightly different patterns of usage as a single meaning”, and “splitting is … dividing or separating them into different meanings” (Kilgarriff 1997:9) Whether lexicographers lump or split senses is a matter of tradition, editorial policy and subjective decisions. E.g. mouth: [body part] /[mouth of a river] / [mouth of a cave] / [mouth of a bottle]

  8. Other linguistic fields with correlating findings Theoretical linguistics: sense enumeration Pustejovsky (1995): conventional lexicon design is based on sense-enumeration. It cannot account for: • the Creative Use of Words, the process of how “words assume new senses in novel contexts” (Pustejovsky 1995:39) • the Permeability of Word Senses: “Word senses are not atomic definitions but overlap and make reference to other senses of the word” (p. 39) • the Expression of Multiple Syntactic Forms

  9. Other linguistic fields with correlating findings Theoretical linguistics: the role of context The context can influence the meaning (based on Cruse 2000:120-123): • selection process: existing readings or established senses are selectively activated and suppressed • coercing a meaning: when the established senses do not fit into the context, the listener is supposed to look for a matching meaning extension, possibly metaphorical or metonymical, “because of a tacit assumption that speakers are usually trying to convey an intelligible message” (p. 120). • Meaning can be modulated in other ways

  10. Other linguistic fields with correlating findings Theoretical linguistics: the role of context Extremist position (non-Crusian): “The notion that words have a meaning – what Lakoff and Johnson (1980) call the “container metaphor” – is now hard to maintain. It seems that “meaning” consists of the process of meaning (Clark 1992). Words should be seen as information tokens that, among others, to some extent guide the meaning process” (Haase and Rothe-Neves 1999:291). Cruse (2000): context-independent “pre-established senses” (p. 68) and “default readings” (p. 116)exist.

  11. Lexical meaning and neuroscience No generally accepted, tested and verified model of word meaning in neuroscience. Cell assemblies are created by correlative coactivation of neurons (Hebb 1949, Pulvermüller 1999, 2001). When a sufficient subset of the assembly is stimulated, the whole assembly ignites and then reverberates. My hypothetical suggestion for the role of a word: igniting, maintaining and modifying spatiotemporal activation of assemblies also biasing further activation. Meaning is selected, coerced and modulated & ambiguity gets resolved in the intricate (but not necessarily linguistically transparent) interplay of neural activations/reverberations.

  12. The HunGram project OTKA (Hungarian Scientific Research Fund) research grant for 2008—2012 (K 72983), PI: dr. Tibor Laczkó Objectives • developing a comprehensive LFG grammar of the Hungarian language (morphology, syntax, lexicon, semantic issues) • implementing it in XLE (LFG parser) Lexical background: non-toy lexicon Single entry for each word unless our grammar needs re-listing (argument structure) Also developing an Artificial Neural Network (ANN) tool that can be trained to learn associational properties of words partly based on information coming from the parser (morphological, syntactic) when analyzing authentic text. Goal: to acquire selectional attributes and important information about the argument structure not otherwise encoded in the lexicon/grammar.

  13. Thank you for your attention. Dr. Ágoston Tóth tagoston@delfin.unideb.hu

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