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Corpora in lexical studies

Corpora in lexical studies

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Corpora in lexical studies

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  1. Corpora in lexical studies Corpus Linguistics Richard Xiao

  2. Aims of this session • Lecture • Corpus-based lexicography • Collocation and colligation • Lab session • Collocation using WST • Collocation using AntConc • Collocation and colligation in Xaira • Using the BNCweb to study collocation

  3. Corpus revolution in lexicographic and lexical studies • Lexicographic and lexical studies are the greatest beneficiaries of corpora • Corpora have “revolutionised” dictionary making and reference publishing • It is now nearly unheard of for new dictionaries and new editions of old dictionaries published from the 1990s onwards not to claim to be based on corpus data

  4. Why use corpora in dictionary making? • Machine-readable corpora allow dictionary makers to extract all authentic, typical examples of the usage of a lexical item from a large body of text in a few seconds • Corpora allow dictionary makers to select entries based on frequency information • Corpora can readily provide frequency information and collocation information for readers • Textual (e.g. register, genre and domain) and sociolinguistic (e.g. user gender and age) information encoded in corpora allows lexicographers to give a more accurate description of the usage of a lexical item

  5. Why use corpora in dictionary making? • Corpus annotations such as part-of-speech tagging and word sense disambiguation also enable a more sensible grouping of words which are polysemous and homographs • A “monitor corpus” allows lexicographers to track subtle change in the meaning and usage of a lexical item so as to keep their dictionaries up-to-date • Corpus evidence can complement or refute the intuitions of individual lexicographers, which are not always reliable because of potential biases in intuitions

  6. Five emphases • Changes brought about by corpora to dictionaries and other reference books - five “emphases” (Hunston 2002) • an emphasis on frequency • an emphasis on collocation and phraseology • an emphasis on variation • an emphasis on lexis in grammar • an emphasis on authenticity

  7. Top 1000 written / spoken words Authentic examples

  8. Corpus-based learner dictionaries • First ‘fully corpus-based’ dictionary • Collins Cobuild English Dictionary (1987) • Some corpus-based learner dictionaries • Longman Dictionary of Contemporary English (3rd edition) • Oxford Advanced Learner’s Dictionary (OALD, 5th edition) • Cambridge International Dictionary of English (1st edition)

  9. Frequency dictionaries

  10. Collocation • Collocation is among the linguistic concepts which have benefited most from advances in corpus linguistics • What is collocation? • strong tea, powerful car (Halliday 1976) • “collocations of a given word are statements of the habitual or customary places of that word…the company that words keep” (Firth 1968:181-2) • “One of the meanings of night is its collocability with dark” (Firth 1957:196) • “a frequent co-occurrence of two lexical items in the language” (Greenbaum 1974:82) • expel a school child vs. cashier an army officer • “I propose to bring forward as a technical term, meaning by collocation, and apply the test of collocability” (Firth 1957: 194)

  11. Meaning by collocation • “There is frequently so high a degree of interdependence between lexemes which tend to occur in texts in collocation with one another that their potentiality for collocation is reasonably described as being part of their meaning” (Lyons 1977: 613) • Complete description of the meaning of a word would have to include the other word or words that collocate with it • “You shall know a word by the company it keeps!” (Firth 1968:179) • Collocation is part of the word meaning

  12. Two types of collocation • Coherence collocation vs. neighbourhood (horizontal) collocation (Scott 1998) • Coherence collocation • Collocates associated with a word (e.g. letter – stamp, post office) • Neighbourhood collocation • Words which do actually co-occur with the word (letter - my, this, a, etc)

  13. Coherence collocation • “A cover term for the cohesion that results from the co-occurrence of lexical items that are in some way or other typically associated with one another, because they tend to occur in similar environments.” (Halliday & Hasan 1976:287) • candle – flame – flicker • hair – comb – curl – wave • sky – sunshine – cloud – rain • Difficult to measure using a statistical formula

  14. Neighbourhood collocation • Collocation in corpus linguistics • Structure of collocation – collocation window • “We may use the term node to refer to an item whose collocations we are studying, and we may then define a span as the number of lexical items on each side of a node that we consider relevant to that node. Items in the environment set by the span we will call collocates.” (Sinclair 1966:415) • Casual vs. significant collocation • Significant collocation: collocation that occurs more frequently than would be expected (in a statistical sense) on the basis of the individual items • n.b. Neighbourhood (horizontal) collocations can include some coherence collocations

  15. Intuition vs. collocation • Greenbaum (1974): “people disagree on collocations” in introspection-based elicitation experiments • Although “collocation can be observed informally” on the basis of intuitions, “it is more reliable to measure it statistically, and for this a corpus is essential” (Hunston 2002: 68) • Intuition is often a poor guide to collocation • “because each of us has only a partial knowledge of the language, we have prejudices and preferences, our memory is weak, our imagination is powerful (so we can conceive of possible contexts for the most implausible utterances), and we tend to notice unusual words or structures but often overlook ordinary ones” (Krishnamurthy 2000: 32-33) • Collocation can be measured on the basis of co-occurrence statistics (MI, z, t, LL etc) – more discussion to follow

  16. Collocation is syntagmatic Langue (Language system) paradigmatic famous boots. Onthe stroke offull time the Stoke the lead onthe stroke ofhalf-time with a goal Smith sin-binned onthe stroke ofhalf-time, added a clinched their win onthe stroke oflunch after resuming chase by declaring onthe stroke oflunch. <p> With a lead expectant crowd, onthe stroke ofmidday. The bird hour began not uponthe stroke ofmidnight but upon the of midnight but uponthe stroke ofnoon. There was, booked in advance. Onthe stroke ofseven, a gong summons Promptly onthe stroke ofsix 'clock, the chooks from Edinburgh onthe stroke ofthe Millennium. Parole (Utterance)syntagmatic

  17. Collocation vs. colligation • Collocation • Relationship between a lexical item and other lexical items • Relationship between words at the lexical level • E.g. verycollocates with good • Colligation • Relationship between a lexical item and a grammatical category • Relationship between words at the grammatical level • E.g. very colligates with ADJ

  18. WST Collocate settings Concord tab

  19. WST collocates Strength of relationship is displayed as 0.000 if it hasn't yet been computed

  20. Strength of collocation relationship A wordlist is required

  21. Highlight and double click…

  22. …to see the selected collocate

  23. Collocates in AntConc

  24. Collocation in Xaira

  25. Colligation in Xaira

  26. Exploring collocation with BNCweb

  27. Search for “sweet”

  28. Concordances of “sweet” KWIC view

  29. KWIC view

  30. Dropdown menu: collocations

  31. Collocation setting

  32. Collocation database (default settings)

  33. Adjusting settings

  34. Noun collocates of “sweet” Click on a word to see its collocation info

  35. Collocation info of “sweet” + “smell” Click on a number to see concordances of collocates at that position

  36. Concordances of “smell” at R2

  37. Collocation statistics

  38. Rank by frequency Frequent words crowd into the top of the collocate list: Are they genuine collocates?

  39. Rank by the t test • Also focusing on frequent words?

  40. Rank by MI Infrequent words at the top of the list How useful are they (especially to English learners)?

  41. Rank by the z score Like MI, the z score also over-estimates infrequent items (e.g. nothings, afton, marjoram)

  42. Log-likelihood test

  43. Rank by MI3

  44. Rank by dice coefficient