One chapter of my Master’s thesis focused on patterns of wh-extraction from the than-complement in English. The basic idea was that different patterns of wh-extraction permit an indirect analysis of the syntax of the than-complement in different comparative constructions. Thanks to all those who helped with grammaticality and acceptability judgements!
English is typologically unusual in permitting wh-extraction from the than-complement in comparative constructions, as in (1).
(1) Who is John taller than?
(1) is a phrasal comparative, i.e. ‘than’ is underlyingly followed by a phrase (as opposed to a clause). Wh-extraction is only permitted from phrasal comparatives, not clausal comparatives, as in (2), the clausal counterpart of (1).
(2) *Who is John taller than is?
Wh-extraction from phrasal comparatives exhibits at least two patterns.
The first is seen in nominal comparatives, as in (3).
(3) a. Who did John give more presents to Mary than?
b. *What did John give more presents to Mary than?
c. *To whom did John give more presents to Mary than?
Wh-extraction of phrasal than-complements which are associated with non-subjects is ungrammatical (or at least degraded), as in (3b) and (3c), whereas wh-extraction of phrasal than-complements associated with subjects is acceptable, as in (3a).
A sub-pattern within nominal comparatives is that, when the nominal modified by more is the (external argument) subject, no wh-extraction (even wh-extraction of subject-associated phrasal than-complements) is possible, as in (4).
(4) *Who did more children give presents to Mary than?
I argued that the patterns in (3) and (4) follow if phrasal than-complements in nominal comparatives are typically small clausal than-complements.
The second pattern is seen in adverbial comparatives, as in (5).
(5) a. Who did John give presents to Mary more than?
b. What did John give presents to Mary more than?
c. To whom did John give presents to Mary more than?
Although the sentences in (5) sound a bit clunky, (5b) and (5c) are significantly better than (3b) and (3c). It seems that wh-extraction from the phrasal than-complement of adverbial comparatives is generally unrestricted.
An important sub-pattern concerns adverbial comparatives with gradable verbs such as like. Compare (6) and (7).
(6) a. John likes chocolate more than Bill.
b. Who does John like chocolate more than?
(7) a. John likes Mary more than Bill.
b. Who does John like Mary more than?
(6a) and (7a) are ambiguous, for example, in (6) Bill could be associated with either the subject John (i.e. John likes chocolate more than Bill does) or the object chocolate (i.e. John likes chocolate more than he likes Bill). (6b) is also ambiguous in the same way, i.e. who can be associated with the subject John or the object chocolate. However, (7b) is unambiguous – it can only have the interpretation where who is associated with the object Mary, i.e. John likes Mary more than he likes who? Descriptively, when the object is [+human], only the object-association interpretation is available for the wh-phrase.
This pattern is not found with non-gradable verbs such as visit, as in (8) and (9).
(8) a. John visits museums more than Bill.
b. Who does John visit museums more than?
(9) a. John visits Mary more than Bill.
b. Who does John visit Mary more than?
(8b) and (9b) are both ambiguous in the same way as (8a) and (9a).
So, the sub-pattern is that wh-extraction of phrasal than-complements is prohibited when the verb is gradable, the direct object is [+human] and the extracted phrase is associated with the subject. I argued that these patterns follow if phrasal than-complements in adverbial comparatives are genuine phrasal than-complements.
In summary, wh-extraction is prohibited from clausal than-complements, but is allowed from small clausal and genuine phrasal than-complements (though it exhibits different patterns concerning the available interpretations of the extracted element). Nominal comparatives may use clausal or small clausal than-complements, whilst adverbial comparatives may use clausal or genuine phrasal than-complements.