Chapter 5 Morphology and Syntax in Neurolinguistics

Types of Linguistic Theories Prescriptive: “prescriptive linguistics” is an oxymoron Prescriptive grammar: how people ought to talk Descriptive: provide account of syntax of a language Descriptive grammar: how people do talk often appropriate for NLP engineering work Explanatory: provide principles-and-parameters style account of syntax of (preferably) several languages

What is morphology? Morphology studies the structures of words in a language (root, affix – prefix and suffix) Example: Nation National International Internationalization Fire fired firing

Linguistic Units Phonetics – phoneme (allophones), distinctive features Phonology – phoneme, distinctive features, syllable … Morphology – morpheme (unit of meaning) Bound morpheme: a morpheme that cannot stand alone as an independent word. Example: -MENT in ship-MENT. Free morpheme: a morpheme that can stand alone as an independent word. Example: car, dog, pick.

Morphological analysis exercise Online exercise: http://www.arts.uwaterloo.ca/~raha/306a_web/morphological.swf

Problematic cases Receive reuse Deceive deconstruction Perform deform

Allomorphs im - plausible im - mature im-possible in - competent il - legal ir - relevant

Word formation rules -Derivation -Compounding -Inflection

What is syntax? Syntax is the study of the principles and rules for constructing sentences in natural languages. While morphology examines how the smallest units of meaning are formed into complete words, syntax looks at how the words are formed into complete sentences.

What is Syntax Not? Phonology: study of sound systems and how sounds combine Morphology: study of how words are formed from smaller parts (morphemes) Semantics: study of meaning of language

What is Syntax? (2) Study of structure of language Specifically, goal is to relate an interface to morphological component to an interface to a semantic component Note: interface to morphological component may look like written text Representational device is tree structure

The Big Picture ? ? ? ? Empirical Matter Formalisms Linguistic Theory Data structures Formalisms (e.g., CFG) Algorithms Distributional Models ? Maud expects there to be a riot *Teri promised there to be a riot Maud expects the shit to hit the fan *Teri promised the shit to hit the fan ? ? Linguistic Theory

Syntax: Why should we care? Grammar checkers Question answering Information extraction Machine translation

key ideas of syntax Constituency (we’ll spend most of our time on this) Subcategorization Grammatical relations Movement/long-distance dependency

What About Chomsky? At birth of formal language theory (comp sci) and formal linguistics Major contribution: syntax is cognitive reality Humans able to learn languages quickly, but not all languages  universal grammar is biological Goal of syntactic study: find universal principles and language-specific parameters Specific Chomskyan theories change regularly General ideas adopted by almost all contemporary syntactic theories (“principles-and-parameters-type theories”)

Basic syntactic structure Subject + Predicate Subject of a sentence is the person, place, object, idea, event that is doing or being something. Predicate is the completer of a sentence. Example: The glacier melted. The glacier has been melting. The glacier melted, broke apart, and slipped into the sea. Interesting cases Flying planes can be dangerous. Colorless green ideas sleep furiously.

Syntactic Trees

Syntactic rules Wh-movement He buys bread. Who buys bread? What does he buy? He buys what? I wonder what he bought. *I wonder he bought what. *I wonder what did he buy.

Types of syntactic constructions Is this the same construction? An elf decided to clean the kitchen An elf seemed to clean the kitchen An elf cleaned the kitchen An elf decided to be in the kitchen An elf seemed to be in the kitchen An elf was in the kitchen

Types of syntactic constructions (ctd) Is this the same construction? There is an elf in the kitchen *There decided to be an elf in the kitchen There seemed to be an elf in the kitchen Is this the same construction? It is raining/it rains ??It decided to rain/be raining It seemed to rain/be raining

Types of syntactic constructions (ctd) Is this the same construction? An elf decided that he would clean the kitchen * An elf seemed that he would clean the kitchen An elf cleaned the kitchen

Types of syntactic constructions (ctd) Conclusion: to seem: whatever is embedded surface subject can appear in upper clause to decide: only full nouns that are referential can appear in upper clause Two types of verbs

Types of syntactic constructions: Analysis NP VP VP an elf V S V S to decide NP VP to seem NP VP an elf an elf V PP V PP to be in the kitchen to be in the kitchen

Types of syntactic constructions: Analysis NP VP V decided PRO to be PP in the kitchen S VP an elf V S seemed NP VP an elf V PP to be in the kitchen

Types of syntactic constructions: Analysis NP VP V decided PRO to be PP in the kitchen S VP an elf V S seemed NP VP an elf V PP to be in the kitchen

Types of syntactic constructions: Analysis NP VP V decided PRO to be PP in the kitchen S NPi VP an elf an elf V S seemed NP VP ti V PP to be in the kitchen

Agrammatism in aphasia Traditional theory Broca’s aphasia Lesion site: Broca’s area in the inferior frontal region (Brodmann’s areas 44 and 45) Symptoms characterized by agrammatism: Sparse speech. Parients tend to speak in very short, simple sentences or even shorter structures mainly containing nouns, main verbs and adjectives, but omitting most grammatical morphemes (such as noun and verb inflections) and so-called function words (conjunctions, articles, etc.).

Paragrammatism in aphasia Traditional theory Wernecke’s aphasia Lesion site: Wernecke’s area in the superior temporal region (Brodmann’s areas 21 and 22) Symptoms (word salad): fluent (oftentimes nonsense) speech. Lacks semantic coherence. Patients tend to speak with frequent self-interruptions, restarts, and circumlocutions, caused by their anomic problems (word-finding difficulties). Grammatical frames appear unaffected.

Problems in traditional theory 1. The relationship between comprehension and production. Are disorders of grammar central, thus affecting both comprehension and production, or can production be selectively disturbed while comprehension is maintained? 2. The relationship between agrammatism and paragrammatism. Are agrammatism and paragrammatism really two fundamentally different phenomena or are they different surface manifestations of grammatical problems that are basically similar but are accompanied by different sets of additional symptoms in Broca’s and Wernecke’s aphasia?

Some findings in aphasia Morphology 1. Free grammatical morphemes (e.g., function words) tend to be omitted, but they are sometimes substituted as well. 2. Bound grammatical morphemes (e.g., inflectional endings) are rarely omitted, but are often substituted.

Syntax 1. Agrammatism (defined only by short phrase length and slow speech rate) seems to exist in most languages and is usually combined with reduced variety in syntax. 2. There is great variation between languages, but a selective vulnerability of grammatical inflections and function words can be found in all aphasics. 3. A substantial number of main verbs are omitted. Many studies give verbs a central role in the formation of the syntactic structure of utterances.

Morphological and syntactic complexity interact Morphological and syntactic complexity interact in making a grammatical structure hard to process. Processing conditions seem to matter in that a. simplification is attempted, and b. complex structures tend to break down and contain many errors. This points to “access problems” as a likely underlying cause.

Theories on agrammatism Mapping hypothesis The main problem in agrammatic comprehension is the mapping of syntactic representations into semantic representations, whereas syntactic parsing is not affected. Good: syntactic processing Good: canonical order processing Bad: lexico-inferential processing of thematic roles Example: The man was eaten by the frog.

Adaptation Hypothesis (Ease of effort) In this framework, agrammatism involves adaptation to the timing deficit. This adaptation to the “reduced temporal window” leads to three types of strategies: 1. simplification: reduced variety, isolated phrases (as a result of preventive adaptation or economy of syntactic computation); 2. restart: faster activation by restarting and profiting from the activation of the first attempt (corrective adaptation); 3. slow rate of speech.

The Trace Deletion Hypothesis and Tree-pruning Hypothesis (Syntactic Trees). The aphasic disturbance specifically affects traces, or the empty positions that are left when movement transformations are performed. When a node is impaired, the tree is “pruned” upward, so that all nodes above it become inaccessible.