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.