Anaphoric dependencies: A window into the architecture of the language system Sergey Avrutin Eric Reuland Frank Wijnen Olga Khomitsevitch Arnout Koornneef Natalia Slioussar Nada Vasic Goals of the course • Explain how language structure and neurocognitive organization can meet • Provide some background on current approaches • Present a number of issues on which current discussions focus Overview • Fundamentals of Linguistics against a neurocognitive background • The grammatical encoding of anaphoric dependencies • Linguistic architecture and cognitive architecture: – Language processing – Language impairment • Acquired • Congenital What is Language? Language: Systematic relation between • Forms: events in an (external) medium (sound, gesture, ink on paper) & • Interpretations: change in information state of the mind How is language represented in the brain? • Reflects general issue of the division of labour between brain areas – Modularity – Functionality – Plasticity Theoretical approach: Minimalist Program The minimal language system PF interface SensoriMotor system C-I interface CHL Interpretation system (system of thought) Lexicon - dedicated +dedicated(?) -dedicated Levelt : Speaking (1989) Task: find map between linguistic operations and neurocognitive processes PF-interface | Computational system of Human Language (CHL) (+Lexicon) | Conceptual-Intentional Interface (C-I interface) ? The triangle of cognitive neuroscience (Hagoort 2003) Computational model Neurophysiology Cognitive Archtecture Behaviour Neural Architecture Neuro anatomy A note on method • The brain is doing a lot at the same time • In whatever you try to measure, you will find a lot of noise • no escape from forming precise (and falsifiable) hypotheses: a theory is your eyes - without it you are blind On the relation between linguistics and psycholinguistics "The split between linguistics and psycholinguistics in the 1970’s has been interpreted as being a retreat by linguists from the notion that every operation of the grammar is a mental operation that a speaker must perform in speaking and understanding language. But, putting history aside for the moment, we as linguists cannot take the position that there is another way to construct mental representations of sentences other than the machinery of grammar. ....There is no retreat from the strictest possible interpretation of grammatical operations as the only way to construct linguistic representations" (Alec Marantz, lecture notes 2000) Correspondence Thesis • Differences between operations within (major) modules of the grammatical system correspond with differences in processes at the neural level and vice versa. (Reuland 2003) In plain language • We have to figure out what the brain does in order to be able to figure out how the brain does it • We have to figure out how the brain does things in order to figure out how it can do what it does • the main danger is not being precise enough on either side Tensions between requirements on Linguistic descriptions • What do we need for easy description? • What do we need for explanation? • Compare - Quantum physics - Newtonian mechanics For understanding planetary motion For understanding why there are no white holes An example: how local are the dependencies we (can) compute? • What did John see? • What did John see – • What did John [ [see - ] ] Issues of this type may occasionally seem abstract but are crucial for our understanding Current views on modularity Is there a division of labour between brain areas? Answer: There is specialisation • Lateralisation: left-right asymmetry • Specialized areas of the cortex: - Motor-cortex - Visual cortex - Auditory cortex Etc. Specialisation within areas Example: (Kandel et al. 2000, Principles of Neural Science; Ch 28): Visual system: specific neurons for: • Black/white detection • Colour detection • Form detection • Depth detection • Movement detection • Facial recognition FUNCTIONS & functions Kosslyn & König (1995) The Wet Mind: • FUNCTIONS (Vision, Hearing, etc. ) v.s. functions (movement detection, depth detection, etc.) • Binding problem: How do the different functions lead to one unified perception? Language: FUNCTION vs functions Is there one language system? Or: • Are there different subsystems that contribute to the FUNCTION Language? • If so, what are the ‘functions’ subserving language? • How elementary are these functions? • Are there any ‘functions’ dedicated to language? Summary of the task • Precise analysis of the operations needed to capture the structure of language • Match these operations with real time processes in the brain • Identify brain areas involved in these processes Methods 1. Grammar: Precise modeling of structure and interpretation 2. Studying “Experiments of nature”: language impairment (genetic, acquired) 3. Behavioral studies: complexity, processing resources 4. Eye-tracking 5. ERP 6. fMRI 7. PET Required for explanation • What do we minimally need to account for language structure? • What do we minimally need to assume is dedicated to language? • Behind these questions: – What kind of elements and what type of properties can be plausibly represented in the brain? The minimalist program Start out assuming: • What has to be the case by conceptual necessity (and no more) • Add no enrichment to the system unless empirically unavoidable • But be as precise as possible Lexicon Lexicon: Atomic form-meaning combinations (morphemes) Each morpheme contains - phonological information how to pronounce (phonology: Sound system will not be discussed here) - grammatical information category (Noun, Verb, Adj., Preposition, etc.), features (person, gender, number, Case, etc.) - semantic information concept, instructions for computation (quantifiers: every, a, some, etc.) The basic combinatory process BINARY OPERATION Merge: a , b a b But: Not all combinations of morphemes are possible words • *real, real-hood, real-able, real-ish, ... • *work, work-ish, work-hood,... • *hold, holded, up-holded | hold, held, up-held • *boy, boy-en | boy, boys Morphemes select what they combine with Hierarchical relations: Tree structures A N boy A -ish N A A un- A N happy ness [N [A unA- [A happy]] –nessN] Syntax: the computational system Basic operation: Merge a,b (= combine a,b) Each combination has a head represented in structure • [A grey] + [N mice] [NP [A grey] + [N mice] ] the N mice is the head of the Noun Phrase grey mice • [V feed] + [NP [A grey] [N mice] ] [VP [V feed] [NP [A grey] [N mice] ]] the V feed is the head of the Verb Phrase An elementary Tree structure V(P) N(P) V feed A grey N mice Basic clause structure 1 Three types of information 1. What happened to whom? Core Predicate - (I saw) Mary feed the cat 2. When did it happen? Tense/Mood - Mary will feed the cat 3. Force: Assertion, Question, Command - (I saw) that Mary fed the cat (I wondered) if Mary fed the cat (I wondered) who Mary fed Basic clause structure 2 Force in root clauses • Ø Mary will feed the cat • Will Mary __ feed the cat • Who will Mary __ feed __ Forming questions requires dislocation Some more examples loveV, BonzoN VP loveV John, [VP loveV BonzoN] BonzoN VP V’ JohnN loveV BonzoN V’ indicates that the construction of the verb phrase continues Terms: Head, complement, specifier Selection Selection restricts possible combinations Syntactic selection: • D selects NP, T selects VP, C selects TP Semantic selection: • John loves Mary • ??The brick loves Mary • John opened the lock/the key opened the lock • ??Serenity opened the lock Dependencies • A fundamental property of all human languages: Dependency Relations. • Local: Semantic roles, Case, agreement, category selection (functional-lexical: D-NP, T-VP) • Non-local: dislocation, anaphors, pronominals • Dependencies are always constrained must be obeyed in putting expressions together Putting expressions together (I saw) John feed Fluffy (bare VP) (I expect) John to feed Fluffy (to + VP but!! mismatch) John will feed Fluffy (T+VP, T takes over, but!! mismatch) John feeds Fluffy (T+VP, but !! mismatch) TP T' T will/to VP V' John V feed Fluffy Rearranging elements (I saw) [John [feed Fluffy]] (bare VP) ------ [John [to [(John) feed Fluffy]]] (to+VP+rearrangement) [John [will [(John) feed Fluffy]]] ([Twill]+VP+rearrangement) [John [(-s) [ (John) feeds Fluffy]]] ([T –s] +VP+ rearr.) TP John T' T to/will/-s VP V' (John) V feed Fluffy Dislocation 1 Dislocation: Mismatch between positions of interpretation and position of realization • Metaphorical term: Movement • Dislocation/Movement expresses Double Duty: Essence: One and the same element is active in two (or more) positions and realized in only one position. Dislocation 2 The specifier of T must be filled: • it will rain • there arrived a man Dual use: re-use an element from the structure TP He T' T will VP V' (he) V love Mary Adding Force: CP 1 • (I thought) [that [TP John would love *(her)]] (........) ---- CP declarative marker: that C' C that TP T' John T would VP V' (John) loveV her Expressing questions: CP 2 • (Mary wondered) [CP ifC [TP John would love her]] (........) ---- CP Question marker added C' C if <+wh> TP T' John T would VP V' (John) loveV her Expressing Questions: CP 3 • (Mary wondered) [whom [TP John would love]] (........) CP whom C - C' TP T' John T would VP V' (John) loveV (whom) How to express dislocation? • (Mary wondered) [whomi [TP John would love - ]] (........) CP whomi C - C' TP T' John T would VP V' (John) loveV - The canonical trace notation • (Mary wondered) [whomi [TP John would love ti]] (........) CP whomi C - C' TP T' John T would VP V' (John) loveV ti The status of traces • What do traces represent? • What kind of elements are they? • Are they needed? If so, why? Answer in Minimalist Program: • Double duty can be expressed without an additional element in the theory • Copies can do the same job Merge: Internal/External traces only for convenience Questions in root clauses • Whom did [John love t] CP whomh C' C didj TP Johni T' T tj VP V' ti V love th Clausal layers Predicational core: verb + arguments Tense/mood layer: coordinates for evaluation Force layer (C): assertion, question, command Movement enables one and the same element to be used in more than one layer • Whomi did [John love ti] Whom: argument of love in predicational core; signals question in Force domain Did: carrier Tense in Tense/mood layer; identifies C in Force domain Wh-movement as an interpretive dependency The interpreter must crucially know: i) a wh-element up front of the clause is part of the Force layer, and must therefore be interpreted as signalling a question; ii) a wh-element up front must be related to a gap (a trace, silent copy, etc.) and his computational system must be able to figure out where that gap is. Some questions and relatives Wh-movement: Movement to a Force position (non-argument: no semantic role, no Case) • Question formation and relativization I wonder [CPwhich mani [ ti read the book]] I wonder [CPwhich booki [the man read ti]] Subject versus object relatives: I admired the man [CPwhoi [ti wrote the book]] I admired the book [CPthati [the man wrote ti]] Structure and processing • What would you predict about the representation of – functional structure versus – core predication by subjects with reduced processing capacity? • They will be selective: functional structure affected Common denominator of processing models • Modularity – language results from a number of specialized components responsible for different aspects of language representation/processing • Major divisions – form (syntax) vs. meaning (semantics) vs. use (discourse) • Hypothesis – Syntax, meaning, and use are subserved by different types of processes • Investigation tool – Dissociability of processing mechanisms Evidence: Neurolinguistics • The study of brain – language relationships through neurological deficits • Prime example: aphasia – A deficit in producing and understanding spoken and written language due to focal brain damage in persons who have gone through normal language development. (Prins & Bastiaanse 1997) – Incidence • approx. 6000 new cases per year in NL • approx. 20.000 patients in NL • Founding fathers of aphasiology: – Paul Broca – Carl Wernicke Paul Broca (1824-1880) • 1861: Broca discovers in a post mortem study (Monsieur Tan) that speech/language (production) is associated with the foot of the 3rd convolution of the frontal lobe – Brodmann’s areas 44 & 45 • today, we call this Broca’s area Mr. Tan’s brain Carl Wernicke (1848-1904) • 1874: Wernicke discovers a second cortical area connected to language: the posterior part of the uppermost temporal gyrus (STG), right behind the primary auditory cortex – Brodmann’s area 22 • today: Wernicke’s area Brodmann’s areas Korbinian Brodmann (1868-1918) Aphasia: syndromes concepts motor images Wernicke-Lichtheim-Geschwindt word images Agrammatism and the CP-layer Question production in agrammatism: The Tree pruning hypothesis, Naama Friedman, Tel Aviv University, Brain and Language 80, 160-187 Patients: Hebrew versus English speakers with similar brain injuries Variable: Wh-questions versus Yes-no Questions English: both involve C Hebrew: only Wh-questions involve C Observations and results Wh-questions (similar for Hebrew and Arabic) (1) H: Miri mecaryeret portret E: Miri draws a portrait (2) H: Mai Miri mecayeret ti : Wh moves to C E: What (does) Miri paint: Wh moves to C Yes/no questions • Usually differ from declarative sentences in intonation only no involvement of C (3) H: Miri mecaryeret portret E: Does Miri draw a portrait: T moves to C Result: In Hebrew only Wh-questions were affected; in English both were structure is reflected in pathology Explanation • Tree pruning hypothesis: The highest nodes of the syntactic tree are inaccessible in agrammatism: CP whh C' C TP Tj Mirii T' T VP tj V' ti V draw th Dependencies: Passive Movement into the subject position T' T VP was V' V' chased DP the mouse Passive morphology: - no semantic role to the subject - no case for the object - double use of the object requirement to move into the Tense system Dependencies: Passive 2 • Movement into the T-system: TP the mousei T' T was VP V' V' DP chased ti Passive morphology to interpreter: - do not assign standard semantic role to the subject - look for a gap - assign to subject the role that otherwise would go to the gap Reversible and non-reversible passives Non-reversible • The apple was eaten by John Reversible • The dog was chased by the cat The ability to process passive morphology is a prerequisite for the correct interpretation of reversible passives Passives and the language system • The prerequisite of being able to accurately process morphology is naturally satisfied in the mature and intact language system, but it need not be met in an immature or impaired system. • Both for young children and for patients with certain types of language impairment this condition may not be met, and hence such speakers may have considerable problems with reversible passives. Passives and agrammatism • A Restrictive Theory of Agrammatic Comprehension, Yosef Grodzinsky, Tel Aviv University and Aphasia Research Center, Boston University School of Medicine, Brain and Language 50, 27-51 Observations (1) (2) Above chance performance The girl pushed the boy Chance performance The boy was pushed by the girl Hypothesis: syntactic movement yields problems More precisely: - traces are invisible to semantic role assignment What do subjects do? Strategy The agent role is the most prominent role in a hierarchy of semantic roles Subjects use this for an auxiliary strategy: Assign the agent role to the leftmost NP of the clause as a default role Result TP T' NPi the boy T was VP V' V pushed PP ti by the girl • The default strategy + correctly interpreting the byphrase ill-formed interpretation guessing A below-chance performance Agrammatic role assignment Normal assignm. a. The mani is pushing the woman | | agent theme <agent, theme> b. The womani is pushed ti by the man | | *agent agent <theme, agent> c. The mani is hated ti by the woman | | *agent experiencer <theme, experiencer> c) yields below chance performance, since agent wins over experiencer Reversibility in wh-movement • The ball that [the boy is kicking t] is red • The cat that [the dog is chasing t] is black The latter also presents problems for Broca’s aphasics Again the trace deletion hypothesis (Grodzinsky et al.) can be adduced: Broca’s aphasics have problems processing traces they use a default strategy to interpret sentences with traces Some Caveats • Lesion in Broca’s area neither sufficient nor necessary to induce syntactic deficits: – Broca’s area is not always lesioned in a clinically significant Broca’s aphasia; – Broca’s area can be affected in patients who do not display a Broca syndrome; most of these patients are mildly anomic. • Severity of morphosyntactic problems in aphasia is correlated with the extent of damage in BA 22. • Also semantic deficits in Broca’s aphasia. Disadvantages of patient studies • damage to neural tissue may not be well delineated (in functional terms) – rather, depends on histological properties or on structure of vascular system • possibility of compensation/adaptation • aphasic symptoms evolve over time (post onset) unclear which symptoms (and hence: processes) are linked to which neural networks Healthy subjects: Imaging studies • PET • fMRI Is Broca’s area the ‘syntax center’? • • • Kaan & Swaab 2002, review (Trends in Cognitive Sciences) perception/comprehension studies; subtraction method paradigms: 1. 2. 3. 4. complex sentences vs. simple sentences sentences vs. word lists jabberwocky/syntactic prose vs. word lists/normal sts syntactic violations vs. correct sentences Where’s syntax in the brain? Overview: Kaan & Swaab 2002, review (TICS) • Broca’s area – NOT necessarily involved in syntactic processing – more activation with more working memory demands • other area’s associated with syntax – – – – anterior temporal lobe anterior parts of BA 21, 22 superior & middle temporal gyri not only Left Hemisphere! Broca’s area … • … is an excitable piece of tissue! (David Poeppel, p.c.) • activated by (i.a.) – – – – word/syllable lists (memory) semantic tasks phonological tasks music perception Suggestions (K&S 2002) • Middle/superior temporal lobe – lexical processing (activating semantic/syntactic, phonological features of words) • Anterior temporal lobe – combining activated information • Broca’s area – storing non-integrated materials • Right hemisphere – – – – prosody ambiguity discourse error detection dislocation/movement • In structural terms: – an element is doing ‘double duty’ by having two copies in the structure – only one of these is spelled out phonetically (ie., has an audible form) • in processing terms: – the processor has to recognize an ‘empty spot’ at the location of the object NP and infer which noun phrase can be connected to it. Electro-magnetic signals • EEG/ERP • (MEG/ERF) 1. Different signatures for syntactic and semantic processing? 2. Autonomy of syntactic processing? EEG ERP (Bressler 2002) • The physiological basis of the cortical ERP: Fields of potential generated by interacting neurons. Field potentials result from the summed extracellular currents generated by electromotive forces (EMFs) in the dendrites of synchronously active cortical neurons. The EMFs, arising from synaptic activation of postsynaptic ion channels, circulate current in closed loops across the cell membrane and through the intracellular and extracellular spaces. Summed closed-loop currents generated by an ensemble of neighboring neurons flow across the external resistance to form the local ensemble mean field potential. • The event-related potential (ERP): Neural signal that reflects coordinated neural network activity. The cortical ERP provides a window onto the dynamics of network activity in relation to a variety of different cognitive processes at both mesoscopic and macroscopic levels on a time scale comparable to that of single-neuron activity. Good: Temporal resolution Bad: Spatial resolution Event-Related Potentials ERP ERP & language: N400 Kutas & Hillyard 1980 N400 • negative(-going) component • peak latency around 400ms • bi-lateral slightly posterior distribution • N400 effect (amplitude modulation): – (mis)match of word meaning with preceding context – semantic priming P600/SPS Osterhout & Holcomb 1993; Hagoort, Brown & Groothusen 1993 P600 • positive(-going) deflection • peak latency around 600ms • bilateral, centro-parietal distribution • grammatical anomalies • ambiguities that are resolved in a dispreferred way • long-distance dependencies ERP: Early Left-Anterior Negativity add picture ELAN • negative(-going) deflection • peak latency around 200ms • left anterior distribution • grammatical violations, e.g. – phrase structure – inflection, function words What do ERPs signify? • physiologically: synchronous post-synaptic activation of several hundreds of thousands of radially oriented pyramidal cells • functionally: No idea! – the brain (groups of neurons) responds in a particular, consistent way to particular stimuli The big picture? (Friederici et al) Linguistic Theory and Neural Activity What can we expect? Very abstractly: •Match between properties of derivations and processes in production or comprehension? •Match at the architectural level - differences between modules involved in a mental computation reflect differences in neural activity