Transcript Pinker_ch7
Notes on Pinker ch.7 Grammar, parsing, meaning What is a grammar? • A grammar is a code or function that is a database specifying what kind of sounds correspond to what kinds of meanings in a particular language 197 • It is not a recipe or program for speaking or understanding. • Procedures are needed for converting thoughts to sounds and sounds to thoughts. • The mental program that analyzes sentence structure during comprehension is called the Parser. Parsing a simple sentence: “the dog likes ice cream.” • Pinker uses his “toy” English grammar. • S->NP VP • A sentence can consist of a noun phrase and a verb phrase. Define a noun phrase NP • NP-> (Det) N (PP) • A noun phrase can consist of an optional determiner, a noun, and an optional prepostional phrase. • Remember this is a “toy” - the real NP would at least look like this: • NP-> (Det) N (PP) (S) • This S allows “recursion” - a sentence to appear inside itself. Define a verb phrase VP VP-> V NP (PP) • A verb phrase can consist of a verb, a noun phrase, and an optional prepositional phrase. Define a prepositional phrase (PP) • PP-> P NP • A prepositional phrase can consist of a preposition and a noun phrase. Nouns (N) • N->boy, girl, dog, cat, ice cream, candy • The nouns in the mental dictionary include boy, girl, dog… Verbs V • V-> eats, likes, bites… • The verbs in the mental dictionary include eats, likes, bites Preposition (P) • P-> with, in , near… • The prepositions include with, in, near.. Determiners (det) • Det->a, the, one…. • The determiners include a,the, one.. The parser works word by word, building a labeled tree. • “The dog likes ice cream.” • Look up ‘the” in the mental dictionary. • The rule says the word ‘the’ is a determiner. “the first twig of the tree” • Det->a, the, one.. The rules tell us what the tree with ‘det’ looks like. • NP->det N NPs can be part of an S, a VP, or PP • Try S->NP VP • The ‘dangling N’ twig predicts the next word is an N. “the dog…. • The next word, dog, fits this prediction. • The NP may be complete and the parser can concentrate on finishing the S. • The NP can have its meaning computed. “likes” • “likes” is a verb and must come from VP • And the tree predicts a NP may be coming next. “ice cream” • The mental dictionary tells us “ice cream” is a N and that fits into the NP. • “when memory has been emptied of all its incomplete dangling branches, we experience the mental “click” that signals that we have just heard a complete grammatical sentence.” Grammatical relationships can be determined from the tree and mental dictionary • Who did what to whom? • ((Who) ((did) (what (to whom?))) Complex sentences • The ‘toy’ grammar does not capture all the basics of human languages. • In particular it lacks the capacity to form complex sentences-- combining two or more simpler sentences into a compound complex sentence. Three types of complex sentences • • • • • • • • • Basic conjunctions S->S1 S2 He went home and she went to lunch. Relative clauses- give info about the head N NP->det N S+pronoun (that, which, who, whom) The dog which () ran away liked ice cream. Complement clauses-directly ‘name’ heads VP->V COMP COMP->that-S The dog (believed (that she would get ice cream.)) ambiguity Sources of ambiguity • Two or more trees can be built from the same word string. • Relative clauses leave more than one gap to be filled • (Loss of inflection on N enable more than one possible grammatical role) • There may be more than one sense (meaning) in the lexicon for a word (morpheme). Homework examples • (see Topic notes on related examples) Gaps and traces • The policeman saw the boy that the crowd at the party accused (trace) of the crime.