Contemporary Linguistics: An Introduction, 5 th edition, Chapter 5: Constraints, 1 Constraints A good deal of research in the field of syntax in recent years has been devoted to determining constraints on the Move operation. One such constraint has been dubbed Shortest move. 1) Shortest move: Moves should be as short as possible. The effects of Shortest move can be seen by considering the following structure, which contains two wh words. 2) [ [ Marvin should give wha to who]] CP IP There is only room for one wh word in the specifier position under CP, but which one is attracted to that position? As the contrast between the following two sentences show, it is the nearer wh word that moves. Sentence 3a) is far more acceptable than 3b), just as we would expect, since it involves the shorter move. Shortest move is sometimes referred to as an Economy Constraint, since it has the effect of making moves as short as possible, which in turn reduces the computational cost of the derivation. Earlier work on transformational grammar identified a number of other constraints on the Move operation. For reasons that we will see shortly, these are traditionally known as island constraints.
Contemporary Linguistics: An Introduction, 5 th edition, Chapter 5: Constraints, 2 To begin, let us consider the following two pairs of sentences. In the first example, the wh word is extracted from a complement phrase and the result is acceptable. In 4b), in contrast, the wh word is extracted from the subject NP. The ungrammaticality of the resulting sentence suggests that it is not possible to move an element out of a subject phrase. We can capture this fact by formulating the following Subject Constraint on transformations. 5) The Subject Constraint: No element may be removed from a subject phrase. A constituent (such as the subject) that does not permit extraction of a component part is called an island. Subject NPs are not the only type of island found in English. As the following examples show, it is also not possible to remove a wh word from a coordinate structure. (As noted in Section 5, a coordinate structure is a phrase in which a word such as and or or joins together categories of the same type.) We can account for these facts by formulating the Coordinate Structure Constraint.
Contemporary Linguistics: An Introduction, 5 th edition, Chapter 5: Constraints, 3 8) The Coordinate Structure Constraint: No element may be removed from a coordinate structure. Clauses that are inside an NP are also islands, as illustrated by the following contrast. This contrast is traditionally captured by means of the Complex NP Constraint. 11) The Complex NP Constraint: No element can be extracted from a CP that is inside an NP. Clauses that serve as modifiers also constitute islands. This can be seen by comparing the acceptability of 12), in which the wh word is extracted from a clause functioning as complement of the matrix verb, with the ungrammaticality of 13), in which the wh word is moved out of a clause that functions as a time adverbial.
Contemporary Linguistics: An Introduction, 5 th edition, Chapter 5: Constraints, 4 This contrast is often stated in terms of the Adjunct Island Condition. (Adjunct is another name for modifier.) 14) The Adjunct Island Condition: No element can be extracted from an adjunct. As might be expected, clauses that are adjuncts and inside a complex NP are especially strong islands. Consider in this regard the following sentence, in which a wh word has been extracted from a relative clause. Yet another constraint is illustrated in the following contrast. As can be seen here, in most dialects of English, a wh word cannot be extracted from the subject position of an embedded clause that begins with an overt complementizer such as that.* Interestingly, there is no such restriction on the extraction of a wh word from the direct object position.
Contemporary Linguistics: An Introduction, 5 th edition, Chapter 5: Constraints, 5 17) a. Who did you say [CP that Jerry was dating t]? b. Who did you say [CP Jerry was dating t]? The contrast illustrated by these examples is often referred to informally as the that-trace filter and stated as follows. (Recall that traces correspond to the gaps left behind by movement operations.) 18) *[CP that t... Understanding precisely why language does not permit that-trace sequences and the other ungrammatical patterns created by extraction is a major goal of contemporary linguistic research. [insert as footnote, *In Appalachian English and Hibernian English, the thattrace filter does not seem to apply. Sentence 16a) Who did you say that left? would be perfectly acceptable in these dialects.]