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Evidence for Item Based Development

Evidence for Item Based Development

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Evidence for Item Based Development

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  1. Evidence for Item Based Development E. Bates and J. C. Goodman, On the Emergence of Grammar From the Lexicon M. Tomasello, The item-based nature of children's early syntactic development

  2. Evidence for Item Based Development • Introduction • What is item-based development? • Studies in Lexically Based Grammar • Studies in Item Based Development • Conclusion

  3. Introduction • What is Item Based Development? • Hypothesis: children’s early utterances are organized around particular words and phrases. Speech is not abstract • So why is early speech perceived as grammatical? • Children imitate and reproduce adult utterances, appearing to posses a knowledge of grammar

  4. Introduction • Item based nature is most evident in the use of verbs • Children tend to retain sampled sentence structure for each particular verb, hence: • A child might use “cut” in the schema Cut___ alone • The same child will use in more complex schemas for “draw” like Draw___, Draw___on____,Draw___for___ • When children learn the determiners a and the, they use each with a different set of nouns, usually mutually exclusive The cat The house The … a dog a plate a …

  5. Introduction • Studies in Italian regarding verb use show that: • 47% of all verbs used, were used in one form only • 40% were used in two or three forms • The remaining 13% were highly irregular forms (frequently used by adults), which could not be learned from generalization • Study group were 3 children, aged 18 months to 3 years • The verbs in question had 6 possible forms (first person singular, second person singular etc…)

  6. Introduction • Transitive and Intransitive • Transitive (Subject-Verb-Object) • Intransitive (Subject-Verb) • Can children use verbs they’ve heard in an intransitive context in a transitive way? • Experiment • Children were introduced a novel verb with a picture. For example “The sock is tamming” with a matching cartoon

  7. Introduction • Later, they were encouraged, with another cartoon, to reply to the question “What is doggie doing?” • We could expect the child to say something like “The doggie is tamming the car” • This would be creative, as the child has taken a novel verb, and taken it into a new, transitive, context • Very few children produced the transitive reply • As a control for these results, other children were exposed to the transitive form, and they had no trouble reproducing it • We’ll return to these studies later

  8. Introduction • Why should we care? • Chomsky’s nativist approach claims • Language acquisition takes place quickly and effortlessly because children have full linguistic competence at birth • Language acquisition relies only indirectly on the language they are exposed to • Children are creative in early stages, because of innate grammar proficiency • Item based development disagrees with this, and questions the presence of adult grammar in children’s language

  9. Definitions • Grammar • Grammar is the discovery, enunciation, and study of rules governing the use of language. The set of rules governing a particular language is also called the grammar of the language.Or as previously described: A set of sentences with a finite structural description. • Lexicon • What words are, how the vocabulary in a language is structured, how people use and store words, how they learn words, the history and evolution of words, types of relationships between words as well as how words are created. • Lexicon is a word of Greek origin (λεξικόν) meaning vocabulary

  10. First Debate • Grammar from the Lexicon • What does this mean? • Grammar has vocabulary qualities • Grammar and vocabulary are learned the same • Same mental mechanisms used for both • Chomsky • Grammar cannot be learned! (in finite time) • It is different from vocabulary

  11. Nature of Debate • Epistemology • Empiricism Vs. Nativism • Plato Vs. Aristotle • Do we have a special grammar organ, or are we just really smart? • Really smart = innate abilities not specific to language • Soft empiricist claim

  12. Emergentism • Emergentism • Solutions to a problem are unpredictable • We will explore the Emergentist approach • Emphasizing the union between grammar and lexicon

  13. The Giraffe • Is the giraffe’s neck a “leaf eating organ”? • Is the giraffe itself a leaf eating organ?

  14. Humans and Giraffes • Hypotheses: Human grammar has evolved like the giraffe’s neck • Human beings have walked into a problem space that other animals cannot perceive • Appearance of language applied pressure on neural mechanisms in the brain • So… • Human beings have symbols for everything • When these symbols appeared together, grammar emerged

  15. Evidence • Two types of evidence • grammar and the lexicon same mental systems (neural mechanism) • Strong relation between grammar/lexical development • Overlap in symptoms of brain damage • The same mental systems for grammar and the lexicon have other roles • Same mental systems do other things

  16. Evidence for Item Based Development • Introduction • Studies in Lexically Based Grammar • Normal Children • Atypical Populations • Lexicon and Grammar in the Adult Brain • Studies in Item Based Development • Conclusion

  17. Studies • Research in normal children • Relation between lexical development and grammar complexity • Target group: normal children, 8 to 30 months of age • Early language development in atypical populations • Comparison with normal children • Early/late talkers, focal brain injury, Williams and Down Syndrome, SLI

  18. Studies • Grammar and lexicon in the adult brain • Does modularization occur in a later stage? • We will examine neurological patients

  19. Development in Normal Children • General Maturation of speech development (English) • Phonology (reduplicative babbling) - 6 to 8 months • Meaningful speech – 10 to 12 months • Additional 4 to 8 months in one word stage • Burst in vocabulary growth (combinations) - 16 to 20 months • Second burst, morphological – 24 to 30 months • Mastering of morphological and syntactic structures – 3 to 3.5 years • Appears like maturation of three mental modules • Phonological • Lexical • Grammatical

  20. Grammar, Comprehension Production • Zones of acceleration for each domain are separated by many weeks • Lets try and find a connection

  21. Vocabulary and MLU • Correlation between vocabulary and MLU • Best indication for 28 month MLU is 20 month vocabulary • Correlation is not cause

  22. Cross Sectional Grammar Complexity • Individual differences around the grammar on vocabulary function are rather small (small s.d.)

  23. Grammar and Expressive Vocabulary • Tight correlation between grammar and vocabulary • Clear dissociation between words comprehended and words produced

  24. Grammar and Expressive Vocabulary • Fan shaped pattern • Implies that word comprehension is a prerequisite for expressive grammar • not sufficient • Comprehension and production can dissociate • Grammar • We expect vocabulary to put a ceiling on grammar complexity, until a threshold is reached • grammar will then decouple with vocabulary • Instead, grammar and vocabulary remain tightly coupled

  25. Important Points • Study follows children through critical stage in development • Is the correlation we found a correlation of grammar with itself? • Vocabulary includes many prepositions, articles and other grammatical words • Removal of such words yields close results • Similar study conducted in Italian • Similar results

  26. Longitudinal Study • We can see that the link between grammar and lexical development extends to longitudinal studies as well

  27. Explaining the Link • Perceptual bootstrapping • Grammatical function words are short, low in stress and difficult to perceive • Logical bootstrapping • Children cannot understand relational terms, until they understand what they relate to. So, grammar depends on the lexicon • Syntactic bootstrapping • Children exploit sentential information to extract the meaning of a novel word. Grammar words are thus obtained

  28. Explaining the Link • Nonlinear dynamics of learning in a neural network • Experiments in neural network learning (even past tense learning) has resulted in non-linear curves • Lexically based grammar • The relation observed would be exactly what we would expect, if grammar is part of the lexicon

  29. Development in Atypical Populations • We would like to find a pediatric population which displays a dissociation between grammar and the lexicon • We shall examine • Late and early talkers • Early focal lesions • Williams Syndrome and Down Syndrome • Specific Language Impairment (SLI)

  30. Late and Early Talkers • Late talkers • Children of age 18 to 24 months who are in the bottom 10th percentile for expressive vocabulary • Early talkers • Children of age 12 to 24 months who are in the top 10th percentile for expressive vocabulary • Do grammar and vocabulary dissociate in these two groups?

  31. Late and Early Talkers • Grammar-on-vocabulary function for two children • Age 16 to 30 months • Age is a poor predictor of vocabulary and grammar

  32. Two Case Studies

  33. Two Case Studies • MW • 17 months old, expressive vocabulary 596 words, MLU 2.13 • SW • 21 months old, expressive vocabulary 627 words, MLU 1.12 • Deductions • It appears that SW is lagging in grammatical development (just begun combining words). Possible dissociation • Despite huge vocabulary, her grammatical level is average for her age • However, SW displays advanced morphology (knows falling and fell) • Dissociation could be explained by short auditory memory • We will use this argument again

  34. Early Focal Lesions • Assuming different neural mechanisms for grammar and vocabulary • We expect to find dissociation between grammar and lexicon, in relation to congenital(Present at birth) brain injuries • We also expect conformity with classic adult aphasia studies (discussed later) • Delay in grammar development for left frontal damage (Broca’s area) • Delay in lexical development for posterior left damage (Wernicke’s area)

  35. Early Focal Lesions • No evidence in favor of predictions • With older children • Plastic reorganization of brain for early focal lesions • Studies conducted during first stages of language acquisition might prove insightful • Lesion site has impact on lingual development • Target group: 10 months to 12 years

  36. Classic Language Areas • Adults suffering damage to Broca’s area usually display inability to produce or comprehend grammatically complex sentences • Damage to Wernicke’s area usually manifests in impairment of comprehension, and natural sounding speech without meaning

  37. Early Focal Lesions • Absence of left right differences • Absence of global differences • Small but reliable disadvantage in word comprehension for right focal damage • Wernicke’s area • Left temporal cortex • Delayed in expressive language (10 to 60 months) • Reliable disadvantage • Broca’s area • No effects recorded for Broca’s Area • Front damage is symmetric for right and left (during 19 to 31 months period) • Conclusion: temporal lobe of left hemisphere is critical, but the frontal lobes become involved in later stages

  38. Early Focal Lesions • Disappearance of left temporal effect • Children with (any) early focal lesion rank below average at the age of 5 to 7 years • Left lesion disadvantage disappears at this age, indicating that some plastic reorganization has taken place (the discussed Wernicke’s area)

  39. Conclusions For Early Focal Lesions • Study group ranks well within 10th to 90th percentile of normal population in grammar-on-vocabulary function • In a normal group of 19 children, we would also expect 1-4 children in the outskirts

  40. Williams Vs. Down • Williams (WMS) and Down (DNS) syndromes • Both constitute a form of genetically based mental retardation • Mean IQ’s between 40 and 60 • Contrast in grammar development • Down • Language abilities below mental age • Severe function word omissions and structural simplifications • Williams • Below mental age • Language abilities surprisingly good compared with other mental abilities

  41. Williams Vs. Down • When do groups separate? • Both groups are late talkers, seriously delayed in word comprehension and production during the infant scale (8 to 16 months in normal children) • Though still 2 years delayed in vocabulary, during toddler scale (16 to 30 months in normal children), WMS children display good grammar capabilities (Within 10th to 90th percentiles) • DNS children remain at a disadvantage • First evidence of dissociation • WMS usually score low on visual short term memory • DNS usually score low on auditory short term memory • A result of perceptual impairment?

  42. Williams Vs. Down

  43. Specific Language Impairment • Definition: A delay in expressive language abilities that is 1 standard deviation below average • The term specific may be misleading • Low attention span also diagnosed • Studies show that grammatical morphology is highly effected • This dissociation can also be explained by a difficulty of processing rapid auditory data

  44. Grammar and Lexicon in the Adult Brain • Conclusions at this point • We’ve seen an interdependence between grammar and lexicon • compatible with unified grammar/lexical approach • Adult neural mechanisms • Does modularization occur in later stages • This is not incompatible with findings so far • We will present two kinds of evidence • Neural imaging of lexical and grammatical processing • Dissociation between lexicon and grammar in patients with focal brain injury (or lack of)

  45. Grammar and Lexicon in the Adult Brain • Some points to keep in mind • All knowledge is in the brain • Short of finding neural activity at birth, can’t know source of knowledge (innate/acquired) • Differences in experience must be accompanied in differences in neural activity • Different responses to two classes of stimuli would require these classes be associated with different patterns in the brain • Different brain activity accounted for • Nouns vs. Verbs • Animal words Vs. Tool Words • High/low frequency words • Classifying by brain activity would result in two many “systems” • Difficulty in classifying by neural activity

  46. Grammar and Lexicon in the Adult Brain • Localization and domain specificity are not the same • If an area is used for language processing, it does not imply dedication • Difficult to prove negative things (like dedication) • Broca’s area known to mediate some motor tasks as well as language

  47. Definitions • Aphasia • Aphasia is a loss or impairment of the ability to produce or comprehend language, due to brain damage. It is usually a result of damage to the language centres of the brain (like Broca’s area).

  48. Different Arguments • Neural Imaging • So far no convincing study conducted • Evidence of dissociation between grammar and lexicon exist, but vary from study to study • Adult aphasia presents a more interesting challenge • Damage to Broca’s area known to create grammatical difficulties • Is Broca’s area central for grammar processing? • Damage to Broca’s area results in processing impairments that transcend language

  49. All Aphasic Patients have Lexical Difficulties • Anomia • Deficit in word retrieval • All Aphasic patients have some sort of Anomia • Hence, a grammar deficit is always accompanied by a lexical deficit

  50. Expressive Agrammatism • Studies in English show that patients of Broca’s aphasia suffer from agrammatism, while Wernicke’s aphasia patients do not • Agrammatism for Wernicke’s aphasia only detected in highly inflected languages (like German and Czech) • English is poor in inflections • So, the above hypotheses is a result of studies conducted in English! • The following table summarizes agrammatism in different populations