Deep Structure and Transformations

Transcription

1 Lecture 4 Deep Structure and Transformations Thus far, we got the impression that the base component (phrase structure rules and lexicon) of the Standard Theory of syntax generates sentences and assigns a syntactic structure (tree diagram or labeled bracketing) to each. This impression must undergo correction. What in fact Chomsky proposed was that the phrase structure rules (and lexicon) generate the Deep Structure of sentences and that the rules of the transformational component of the syntax map these deep structures onto Surface Structures. In this way, each sentence has both a deep structure and a surface structure representation. In what follows we shall consider the role played by deep structures and transformations and surface structure. In his "Aspects of the Theory of Syntax" Chomsky argued that a descriptively adequate grammar must, among other things, define the notion of 'grammatical sentence' and assign to each and every sentence a structural description that correctly reflects the native speaker's knowledge of syntactic structure as evinced in his performance. To achieve this requirement more and more rules should have been added to the set of PSRs mentioned above. To circumvent the proliferation of PSRs, Chomsky made the rule system of the grammar recursive, as seen above. Nevertheless, some real problems remained. Consider sentences such as (1-2): (1) The police believed John put the money in his pocket (2) What did the police believe John put in his pocket? The lexical entry for the verb put would include the syntactic information provided by a PSR such as VP V NP PP and by its subcategorization frame (put: V, + [ NP PP]). A sentence such as (36) raises no problems of principle. The verb put requires a particular complement structure: this structure is realized by an NP and a PP which appear adjacent to one another as 'sisters' under a common 'mother':

2 (3) VP V NP PP put This is the simplest case of relationship between a verb and its complements: because all the three elements together form a VP it is possible to formulate its appropriate phrase structure rule, and because the complements appear next to the verb it is possible to specify the verb's subcategorization frame in a straightforward manner. The problems begin with sentence (2) (our discussion follows Horrocks (1987)). The characteristic of this sentence is the fact that its direct object NP is not where we would expect it to be on the basis of the subcategorization frame assigned to the verb put. It is customary for interrogative expressions (most if which begin with wh-) to appear at the beginning of a sentence regardless of their grammatical functions. Thus, in (2) what is the direct object of put, just as the money is the direct object of put in (1). Yet, it occupies the first position in the sentence and there is a 'gap' in the NP position after put where we might otherwise expect the direct object to be. Thus, one of the tasks of a descriptively adequate grammar is to show that the relationship between put and what in (2) is a more complex version of the relationship between put and the money in (1). This can not be achieved using only the resources provided by the phrase structure grammar and the associated lexicon. To solve these problems, Chomsky proposed the introduction of transformational rules into the theory of syntax. Beginning with 'Aspects' he drew a clear-cut distinction between the deep structure and the surface structure of a sentence. The basic idea is quite simple. We have already seen that in a sentence such as (43): (4) What did John put in his pocket? there is essentially the same relationship between put and what as there is between put and his money in (5):

3 (5) John put his money in his pocket Clearly, in (5) we have to do with a simple case, in that the related lexical items are adjacent to one another as 'sisters' within a VP. In contrast, in (4), the relationship is more complex in that the direct object has been displaced from its 'basic' position. We hypothesize that every sentence has two syntactic representations: one at which the simple, 'basic' relationship between items holds by definition and another at which more complex versions of this relationship may optionally be involved. Let us call the first the sentence's deep structure and the second its surface structure. Thus, (4) would have the deep structure (6) below: (6) DS S NP (Aux) VP V NP PP John put what in his pocket and the surface structure (7) below, where the DO position is occupied by later on to be called the trace (t) of the moved NP: (7) SS NP S S Aux NP VP V NP PP what did John put in his pocket

4 The exact position to which wh-expressions move will be made explicit immediately below. On the other hand, (5) above would have a deep structure identical to its surface structure, namely (8): (8) DS/SS S NP (Aux) VP V NP PP John put the money in his pocket Thus, the essential sameness between sentences (4) and (5) above is that at deep structure (6)/(8) the same relationship between put and its direct object is expressed: the direct object NPs appear in precisely the same configuration with respect to the verb put. The essential difference between (4) and (5) is that at surface structure (7)/(8) the displacement of the direct object in (4) is signaled by its occupying a different position when compared to its position in (5). To establish the relationship between deep structures such as (6) and surface structures such as (7) we have to set up a transformational rule to spell out this relationship. Another famous example where we need the level of deep structure level of analysis is the discontinuous constituent embodied by the Auxiliary [Aux] in English. The Aux is that constituent which includes the elements of tense, modality and aspect of a sentence. The phrase structure rule for VP indicates that its constituents are grouped into the following sub-strings: (a) the Aux and (b) the Main Verb. The Aux is a discontinuous sequence of affixes (bound morphemes: -s, -ed, -en, -ing) that alternates with auxiliary verbs (free morphemes: modals, aspectual auxiliaries: have and be). The sequence of the Aux has its precise inner ordering at deep structure and it precedes the Main Verb:

5 (9) Aux Tense (Modal) (have-en) (be-ing) In finite clauses Tense is obligatory; all the other elements, Modals and Aspect auxiliaries combine with tense and they are optional. In order to secure this we have to place Tense in initial position in the Aux node expansion. The deep structure sequence of Aux differs from its surface structure. Compare the left sequences to the corresponding surface forms below: -ed run ran -ed have-en run had run -ed be-ing run was running A local transformation called Affix Hopping has to apply in order to rearrange the elements in the Aux sequence so as to eliminate all discontinuities and secure thereby the proper surface structure. This is obtained by hopping the affix over the single verbal element to the right of it and attaching the affix to it. For example, the deep structure of sentence (10) is given in (11) and its surface structure in (12): (10) Mary might have been working (11) DS S NP VP Affix Hopping Aux MV T M Perf Prog Mary -ed may have-en be-ing work (12) SS S

6 NP VP Aux MV M T Perf V Mary may + ed have be + en work + ing So far so good. However, we have already seen that the information contained in PSRs duplicates the information provided by the subcategorization frames of individual verbs. At the right moment we noticed that this id an undesirable result. This redundancy has, somehow, to be done away with. It is known that any grammar should mediate between meaning and sound. GT Grammar did this mediation by postulating a D-str (in fact the input to the Semantic Component) and a S-str (in fact the input to the Phonological Component) related by transformations which converted D-str into S-str. In what follows we try to illustrate why we have to get rid even of transformation. One of the most important properties of transformation rules should be their quality of preserving the meaning of sentences: they operated on D-str and can only 'see' the D-str. Let us take a couple of examples and see whether transformations are truly 'meaning preserving' in any circumstances. Our first example analyses the Passive Transformation. Consider the following example: (13) John broke the window (we assume the sentence as true) The window was broken by John (we also assume the sentence as true) There are, however, counter-examples to the "meaning preserving" of the Passive Transformation. Consider the following sentences: Passive (14) Many arrows did not hit the target (but many did = true) The target was not hit by many arrows (but few did = true)

7 We notice that the rule of Passivization has changed the interpretation of the sentence. The presence of negation (which is a VP operator) and of the quantifier many (which is a sentence operator) determine the change in interpretation of the two sentences. An operator is higher in the structure of a sentence and has to take scope over the constituents it refers to. Thus, the difference between our active and passive sentences is given by the different order of the two quantifiers. In the active sentence many is not in the scope of negation but outside it. In the passive construction, the quantifier many is in the scope of negation and gets itself negated. We see that the linear order of constituents may be significant for the interpretation of strings. Let us provide another example: (15) Everybody in this class speaks two languages (two different languages = true) Two languages are spoken by everybody in this class (the same two languages = true) We see again that the intervention of quantifiers (everybody and two) and their different order create difference in scope. Finally, let us take another example which does not concern quantifiers or negation but still involves passivization: (16) The tribe willingly sacrificed Harry (we understand 'willingly' as being oriented to the subject i.e. the tribe) Harry was willingly sacrificed by the tribe ('willingly' is ambiguous as being either oriented to the subject or to the PP i.e. by the tribe). We see again that a different order of words engenders a different interpretation. We conclude that the S-str of a sentence may be significant for semantic interpretation because the relative scope of operators is specified at this level. The S-structure is produced by transformations; however, one can no longer maintain the claim that transformations are meaning preserving.

8 Preliminaries to "Government and Binding" Grammar (Chomsky (1981)). Of late, linguists have put forth the idea that S-str is richer in semantic information than D-str because S-str also shows the relative order of the operators. This theoretical position is supported by the fact that the information present at D-str is preserved at S-str by the use of traces. To see the relevance of this new theoretical position which states that S-str is richer in semantic information, consider the following sentences: (17) a. John drives the car easily b. The car drives easily It is clear that in the first sentence 'easily' refers to John's ability to easily drive the car; in the latter sentence, 'easily' refers to the properties of the car which make it be driven easily by anyone. Notice, however, that the car is the Patient in both constructions. Thus, whether the car is object or subject, its interpretation is the same (i.e. Patient). The various properties of NP are scattered in the two structures but depend on the relations that hold between NP and its trace at S-str: Adapting the representation of sentence (17b) to Chomsky's old format of sentence structure, its representation will look like the PM bellow: DS S NP VP Aux MV AdvP -s V NP drive the car easily In such a construction, the verb drive lacks the ability to assign case to the car and thus keeps it in this lower position; drive becomes, in this case, an intransitive verb and the sentence lacks a subject, which makes it ill-formed. The only way to obtain the well-

9 formed sentence is to move the car into the subject NP position. The PM of the SS of (17b) is: SS S NP VP the car i Aux MV AdvP -s V NP drive t i easily We see that S-str is more informative semantically because through the use of the trace the NP (in our case the car) is still interpreted as Patient. Through its position occupied in both representations easily characterizes the subject, as in both representations there is the same scopal relationship between the subject and the AdvP. Government and Binding grammar (GB) operates with 'chains'. A chain consists of the head of the chain (the lexical item) and one or several traces. We have come to see the different view in which GB grammar is organized: Lexicon project D-str Move α S-str

10 LF PF Transformations were given up in favour of the operation Move α (as illustrated in the above example: The car drives easily). This rule of GB simply says that we can move any constituent anywhere. It is the task of the principles of grammar to state conditions on the possible movements. GB is viewed as a modular structure. It consists of several sub-theories (i.e. modules). Each module contains principles and may also specify parameters, that is dimensions of variation among languages.