When more is used alone as an adverb, it must also occur after the verb phrase. Also, it appears that adverbs modified by more and less have the same distribution as when they are not modified. However, the than portion of an adverbial comparative is restricted to post verb phrase positions. The first observation can be captured by having more and less select only vxARB from the set of adverb trees. Comparativization of adverbs looks very similar to that of other categories, and we follow this trend by giving the tree in Figure 23.11(a), which parallels the adjectival and nominal trees, for these instances. This handles the quite free distribution of adverbs which have been comparativized, while the tree in Figure 23.11(b), vxPnx, allows the than portion of an adverbial comparative to occur only after the verb phrase, blocking examples such as ((501)).
|(a) CARBarb tree||(b) vxPnx tree|
The usage of the compar feature parallels that of the adjectives and nominals; however, trees which adjoin to VP are compar- on their root VP node. In this way, vxPnx anchored by than or as (which must adjoin to a compar+ VP) can only adjoin immediately above a comparative or comparativized adverb. This avoids extra parses in which the comparative adverb adjoins at a VP node lower than the than-clause. A final note is that as may anchor vxPnx non-comparatively, as in sentence ((502)). This means that there will be two parses for sentences such as ((503)).
This appears to be a legitimate ambiguity. One is that John works as quickly as a carpenter (works quickly), and the other is that John works quickly when he is acting as a carpenter (but maybe he is slow when he acting as a plumber).