Heavy NP shift

Heavy NP shift is an operation that involves re ordering (shifting) a "heavy" noun phrase (NP) to a position to the right of its canonical position under certain circumstances. The heaviness of the NP is determined by its grammatical complexity; whether or not shifting occurs can impact the grammaticality of the sentence. Ross (1967) is thought to have been the first to systematically investigate the properties of heavy NP shift. Although the term heavy NP shift derives from the theoretical framework of transformational grammar, which describes the process in terms of movement of the NP, linguists working in other frameworks also use this term. And in approaches to syntax where NP is analyzed as a determiner phrase (DP), heavy NP shift is called heavy DP shift.

Early observations of weight or heaviness have been credited to a rhythmical feel that unconsciously takes shape in languages, that is, the tendency of growth, to go from shorter to longer elements within a phrase. In these early observations, it was noted that when there are two constituents differing in size, the smaller constituent usually precedes the longer one. This observation has been more recently coined as the "principle of end weight". The literature proposes many different definitions of weight or heaviness such as number of words in the NP (length of NP), number of nodes in the NP, and more generally number of phrasal nodes. Other observations on heaviness include:

According to Chomsky (1975), the separability of the indirect object is determined by the complexity of the direct object (NP). It is not length in words but rather the complexity of the object that determines the "naturalness of formation". ex: "They brought all the leaders of the riot in" appears more natural than "They brought the man I saw in." According to Chomsky (1975), the constituent [the man I saw], although shorter than the constituent [all the leaders of the riot], is more complex.

The relative weight of post verbal constituents influences their order, not the weight of any one constituent such as NP. One study found that independent of NP length and complexity, the NP did not shift unless it was at least 4 words longer than the surrounding material. ex: The canonical phrase, I gave NP[the valuable book that was extremely difficult to find] PP[to Mary], is more likely to shift the heavy NP to the end of the phrase since the NP is more than 4 words longer than the following prepositional phrase (PP).

A theory of Early Immediate Constituents (EIC) seeks to explain word order variation at a phrase level of grammaticalization or more simply, a "save the hardest for last" approach. Constituents are syntactically grouped so they can be recognized and produced rapidly and efficiently as possible. The parser must analyze the VP and its immediate constituents then calculate how early the listener will be able to identify all the constituents by counting the number of words it takes until all immediate constituents (IC's) are recognizable. ex: According to EIC, the phrase, [I gave1 to2 Mary3 the4 valuable book that was extremely difficult to find] is easy to remember because this phrase only requires 4 words (indicated by subscript numbers) to find all IC's. Compare this to, [I gave1 the2 valuable3 book4 that5 was6 extremely7 difficult8 to9 find10 to11 Mary], which requires 11 words to find all IC's. According to the EIC, the first example is preferred because it is easier to comprehend. The EIC theory also proposes that word and constituent order varies cross linguistically and is dependent on whether a language is head final (such as Japanese and Korean) or head initial (such as English).

Pragmatic effects have been thought to influence heavy NP shift. According to this theory, items are sequenced so unpredictable content (new or important information) precedes predictable content (old or unimportant information).

German word order is variable and flexible and relies on a rich inflectional system. Rearrangements of an NP and PP can take place similar to English i. e. [NP PP V] or [PP NP V]. German does not allow a direct object NP to the right of a final verb. The examples below show the rearrangement of a heavy NP and a PP. Either order is acceptable in German as word order variation is not as strict as it is in other languages such as English.

For analyses that treat heavy NP shift as movement, there are two kinds of shifts when considering heavy NPs: one involves rightward movement, the involves leftward movement.

The first, and most traditional, is when a "heavy" object NP is shifted rightward to the end of the utterance. According to one theory a complex NP will be shifted rightward if it does not cross over a verb. Another theory proposes a leftward movement of a "light" indirect object. According to this theory an indirect object is moved leftward independently of verb movement to a higher specifier position, next to the verb and before the direct object, leaving the heavy NP in situ. This syntax tree shows an example of rightward movement of a heavy NP. The entire constituent my rich uncle from Detroit has 'shifted' from its position as a complement to the verb to an adjunct of the VP. This tree has been created using a particular style of syntax, mainly X bar Theory.

The syntax tree below shows an example of leftward movement of a 'light' indirect object. The constituent on the street has 'shifted' from its position in a small clause environment past the direct object to a higher functional specifier position leaving the 'heavy NP' in situ. This syntax tree has been created using a particular style of syntax, mainly X bar Theory.