Lecture 6: Syntax II

Outline

Extending the Phrase Structure Rules
Recursive Rules
Ambiguity

0. Goals of Syntax (repeated from before)

generating (un)grammatical sentences
explaining creativity
explaining ambiguity
cross-linguistic differences

1. Extending the Phrase Structure Rules

1. So far we have the rules

a. S --> NP VP

b. NP --> Det N

c. NP --> N

d. VP --> V NP (this is the rule for a transitive verb)

e. VP --> V (this is the rule for an intransitive verb)

2. This allows us to generate sentences like:

a. The dog chased the cat.

b. Wallace fed Gromit.

These rules allow us to generate very many, but a still finite number of sentences (with 1000 nouns we can create 1,000,000 subject-object combinations).

3. Adding more verb types: verbs which require two obligatory phrases after them. These are known as ditransitive verbs.

a. VP --> V NP NP

b. VP --> V NP PP

4. This now allows us to generate sentences like:

a. Wallace gave the cheese to Gromit.

b. Wallace gave Gromit the cheese.

c. Wallace bought Wendolene a ring.

With these extra VP rules we can generate many more sentences, but it is still logically possible to list all of the sentences that this grammar can generate ... until we add the rules in the next section.

2. Recursion

Another verb type takes units rather like sentences as the complement of the verb. A verb like 'realize' is followed by a unit that is just like a sentence, except that it additionally starts with the word 'that'. Many other verbs also take sentential complements.

a. Wendolene realized that Wallace fed Gromit.

b. Preston wonders whether Gromit is afraid of him.

c. Wallace asked if the sheep were in the warehouse.

Words like 'that', 'whether', and 'if' that are used to introduce embedded sentences (often known as 'embedded clauses') are called complementizers, and they are combined with a sentence using a rule like (6), creating an enlarged sentence category, often known as S' (read "S-bar").

6. S' --> Comp S

One special property of this rule is that it allows us to place a sentence (S) inside a larger sentence. And if we do this once, we can do it again. In fact, we can embed one sentence inside another again and again without limit, if we are so inclined! This property of syntactic rules is known as recursion. [Recursion: property of recurring.] [Note: in order to combine an S' with a verb, we also need the new VP rule VP --> V S'.]

7. Preston knows that Wendolene realized that Wallace fed Gromit.

Now we can generate INFINITELY many sentences

So far only dealing with obligatory requirements of verbs: the NPs, PPs, S's etc. that a verb must combine with are known as arguments of the verb. The following examples show that when one of the arguments of a verb is missing, the sentence becomes ungrammatical.

8. subjects

a. *fed Gromit

b. *slept

9. objects

a. *Wallace fed (Gromit)

b. *Wallace gave Gromit (cheese)

More recursion: in addition to the arguments of a verb, there are other phrases that can be optionally included in a sentence. These optional phrases, like the PP in (9b) are often known as modifiers. The PP modifier in (9b) describes where the action described by the verb takes place.

9a. The cat sat

9b. The cat sat on the mat

10.

a. VP --> VP PP

can apply to itself

b. The cat sat on the mat in the morning

c. The cat sat on the mat in the morning during the summer

Goes with different kinds of VPs

d. The cat chased the dog in the morning (transitive VP)

e. The cat put the ball in the box in the morning (ditransitive VP)

f. The cat realized [that the dog takes naps in the afternoon] in the morning (sentential complement VP: note that the PP "in the morning" modifies the VP in the main clause, not the VP in the embedded clause).

Another way of generating infinitely many sentences

Evidence for recursive VP structure: VP-deletion

We can show evidence to confirm the claim that when a PP combines with a VP to modify the meaning of the VP, the VP and the PP together form another VP. Recall from the last class that in sentences like (11a), a VP may be replaced by the auxiliary verb do. Now look at the sentences in (11b-f) and see what 'do' is standing in for. As you see, 'do' can stand in for strings like 'chased the dog', but it can also stand in for longer sequences like 'chased the dog in the park in the morning'. If we're right in our assumption that 'do' substitutes for phrases that are VPs, then we can conclude that all of these strings are VPs.

11.

a. The cat chased the dog, and the ferret did too.

did = chased the dog

b. The cat chased the dog in the morning, and the ferret did too.

did = chased the dog in the morning

c. The cat chased the dog in the morning, and the ferret did in the afternoon

did = chased the dog

d. The cat chased the dog in the park in the morning, and the ferret did in the living-room in the afternoon

did = chased the dog

e. The cat chased the dog in the park in the morning, and the ferret did in the afternoon

did = chased the dog in the park

f. The cat chased the dog in the park in the morning, and the ferret did too.

did = chased the dog in the park in the morning.

3. Ambiguity

Modifiers for NP or VP: account of ambiguity

12.

a. The dog in the park chased the cat

The NP 'the dog in the park', in which the PP 'in the park' modifies the meaning of the NP 'the dog', can be generated if we add to our little grammar a rule which allows PPs to combine with NPs, much in the same way that we have already seen them combining with VPs. This can be expressed in a rule like (12b).

b. NP --> NP PP

This now allows us to give an explanation for ambiguous sentences like (12c). The PP 'in the park' could be in the structure as an NP-modifier or as a VP-modifier.

c. NP or VP modifiers

The cat chased the dog in the park