"Heavy NP shift" is a term used within the tradition of transformational grammar to describe a process which "shifts" Noun phrases (NPs) to the right of their usual position under certain circumstances. Typically, the process applies to large, complex NPs (i.e. NPs which are "heavy"). The following pair shows (a) a sentence without heavy NP shift and (b) the same sentence after the operation has applied:

1. (a) I gave the books which my uncle left to me as part of his inheritance to Bill

1. (b) I gave to Bill the books which my uncle left to me as part of his inheritance

The operation cannot usually apply to smaller NPs, as shown by the unacceptability of (2b):

2. (a) I gave the books to Bill

2. (b) * I gave to Bill the books

In the preceding examples, heavy NP shift has inverted the order of the direct object and indirect object. The operation can also invert the order of the direct/indirect object and an adjunct:

3. (a) I talk all the time to my uncle who left me an enormous inheritance

3. (b) I understand perfectly the mathematical model of ideal gasses presented by Prof. Smith

John R. Ross observed that heavy NP shift obeys a "right roof constraint"; that is, an NP cannot be shifted outside of its containing clause, as shown by the unacceptability of (4b):

4. (a) The fact that John gave to Bill the books which my uncle left to me is of no consequence

4. (b) * The fact that John gave to Bill is of no consequence the books which my uncle left to me

Analyses of heavy NP shift

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There have been a number of different analyses of heavy NP shift within generative syntax. The traditional assumption was that there is a rightward movement operation (i.e. a transformation) which optionally moves any heavy NP to the right edge of the Verb phrase in which it occurs. In an alternative formulation, heavy NP shift may apply freely to any NP regardless of weight, but light NPs which undergo shifting are filtered out in the phonological component. More recently, Richard Larson has suggested that sentences such as (1b) are derived as follows using only leftward movement:

the books which my uncle left to me as part of his inheritance gave to Bill

Verb and indirect object move to the left together →

gave to bill the books which my uncle left to me as part of his inheritance

Subject is added →

I gave to bill the books which my uncle left to me as part of his inheritance

This analysis has the benefit of explaining Ross's right roof constraint without stipulation. It has become especially popular following the ban on rightward movement imposed by Richard Kayne's theory of Antisymmetry.

Larson's analysis of heavy NP shift has been criticized by Ray Jackendoff, amongst others. Jackendoff argues that heavy NP shift does not result from movement, but rather from a degree of optionality in the ordering of a verb's complements. The preferred order in English is for the indirect object to follow the direct object, and for adjuncts to follow objects of all kinds, but if the direct object is "heavy", the opposite order may be preferred (since this leads to a more right-branching tree structure which is easier to process).

A mysterious property of heavy NP shift is that, in the case of ditransitive verbs, a shifted direct object prevents extraction of the indirect object via wh-movement:

1. Who did you give the books written by the venerable Prof. Plum to?

2. * Who did you give to the books written by the venerable Prof. Plum?

This would arguably be unexpected if heavy NP shift merely resulted from optionality in complement ordering, or from a rightward movement operation. Larson's analysis may be able to explain this restriction.

References

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linguistics