Looking at these examples, we are tempted to produce a tree for this construction that is similar to ARBaPa. However, it is quite common for the than portion of these comparatives to be left out, as in the following sentences:
Furthermore, than NP cannot occur without more.
These facts indicate that we can and should build up nominal
comparatives with two separate trees. The first, which allows a
comparative adverb to adjoin to a noun, is given in
Figure 22.3(a). The second is the noun-phrase modifying
prepositional tree. The tree CARBn is anchored by more/less/fewer and CnxPnx is anchored by than. The
feature compar is used to ensure that only one CARBn tree
can adjoin to any given noun--its foot node is compar- and the
root node is compar+. All nouns are compar-, and the compar value is passed up through all trees which adjoin to N or NP.
In order to ensure that we do not allow sentences like *Vikings than mongols eat spam, the compar feature is used. The NP foot
node of CnxPnx is compar+; thus, CnxPnx will
adjoin only to NP's which have been already modified by CARBn
(and thereby comparativized). In this way, we capture sentences like
((416)) en route to deriving sentences like ((410)), in a
principled and simple manner.
Sometimes the missing noun refers to an entity or set
available in the prior discourse, while at other times it is a
reference to some anonymous, unspecified set. The former is
exemplified in a mini-discourse such as the following:
Calvin: ``The mongols ate spam.''
Hobbes: ``The vikings ate more.''
The latter can be seen in the following example:
Calvin: ``The vikings ate a a boar.''
Hobbes: ``Indeed. But in fact, the vikings ate more than a boar.''
Since the lone comparatives more/less/fewer have the same basic distribution as noun phrases, the tree in Figure 22.4 is employed to capture this fact. The root node of CARB is compar+. Not only does this accord with our intuitions about what the compar feature is supposed to indicate, it also permits nxPnx to adjoin, giving us strings such as more than NP for free.
The structures are given in Figure 22.5. Also,
it will block strings like more men and women than children under the (impossible) interpretation that there are more
men than children but the comparison of the quantity of women to
children is not performed. Unfortunately, it will permit comparative
clauses such as more grapes and fewer than avocados under the
interpretation in which there are more grapes than avocados and fewer
of some unspecified thing than avocados (see Figure 22.6).
In a sense, this is actually only simulating the ellipsis of these constructions indirectly. However, consider the following sentences:
The first of these has a pro-verb phrase which has a nominative subject. If we totally drop the second verb phrase, we find that the second NP can be in either the nominative or the accusative case. Prescriptive grammars disallow accusative case, but it actually is more common to find accusative case--use of the nominative in conversation tends to sound rather stiff and unnatural. This accords with the present analysis in which the second noun phrase in these comparatives is the complement of than in nxPnx, and receives its case-marking from than. This does mean that the grammar will not currently accept ((424)), and indeed such sentences will only be covered by an analysis which really deals with the ellipsis. Yet the fact that most speakers produce ((425)) indicates that some sort of restructuring has occured that results in the kind of structure the present analysis offers. There is yet another distributional fact which falls out of this analysis. When comparative or comparativized adjectives modify a noun phrase, they can stand alone or occur with a than phrase; furthermore, they are obligatory when a than-phrase is present.
Comparative adjectives such as better
come from the lexicon as compar+. By having trees such as
An transmit the compar value of the A node to the root
N node, we can signal to CnxPnx that it may adjoin when a
comparative adjective has adjoined. An example of such an adjunction
is given in Figure 22.7. Of course, if no
comparative element is present in the lower part of the noun phrase,
nxPnx will not be able to adjoin since nouns themselves are
compar-. In order to capture the fact that a comparative
element blocks further modification to N, An must only adjoin
to N nodes which are compar- in their lower feature matrix.