Locality Constraint On Movement Evidence From English
Introduction
Locality constraints on movement in syntax are a cornerstone of modern linguistic theory, particularly within the generative grammar framework. These constraints dictate that movement operations, such as wh-movement or head movement, are not unbounded but rather adhere to specific locality conditions. In simpler terms, a constituent cannot move arbitrarily far in a sentence; it must move to a position that is 'close enough' in a structural sense. This article will delve into the simplest evidence from English that supports the existence of locality constraints on movement. We'll explore how constituents move to the next-highest phrase immediately containing them, and what happens when movement violates these locality conditions. This exploration will not only solidify our understanding of movement phenomena but also shed light on the intricate architecture of the human language faculty.
Understanding Movement and its Significance
Movement is a fundamental operation in syntax, allowing us to derive various sentence structures from an underlying base structure. For instance, consider questions like "What did John buy?" The wh-phrase "what" originates within the verb phrase (VP), as the object of the verb "buy," but it moves to the beginning of the sentence to the specifier position of the Complementizer Phrase (CP). This movement is not random; it follows specific rules and constraints. If movement were unconstrained, we would expect to find sentences with wh-phrases appearing in completely unpredictable positions, which is not the case. The fact that movement is constrained suggests that our minds employ a structured system to generate and interpret sentences. The significance of understanding movement lies in its ability to reveal the underlying principles that govern sentence formation, providing insights into the cognitive mechanisms behind language. By examining phenomena like wh-movement, we can uncover the deep-seated rules that shape our linguistic competence.
The Core Idea of Locality
The core idea behind locality constraints is that movement must be local. A constituent moves to the "closest" available position that satisfies the requirements of the grammar. This 'closeness' is not measured in linear terms (i.e., the number of words), but rather in structural terms, based on the hierarchical organization of the sentence. The most common way to express this is in terms of phases. Phases are syntactic constituents (CP and vP being the most commonly assumed phases) that act as domains for syntactic operations. Movement typically occurs to the edge of a phase before moving further. This stepwise movement ensures that the moving constituent remains within the locality domain. For example, if a wh-phrase needs to move from deep within a sentence to the beginning, it will first move to the edge of the closest phase containing it, and then to the edge of the next higher phase, and so on, until it reaches its final destination. This phased movement accounts for many of the locality effects observed in natural languages.
Simplest Evidence from English
Wh-Movement and Superiority
The simplest evidence for locality constraints in English comes from wh-movement, specifically the phenomenon known as superiority. Superiority effects arise in multiple wh-questions, where there are two or more wh-phrases (e.g., "who," "what," "which"). Consider the following pair of sentences:
- Who bought what?
- *What did who buy?
Sentence (1) is grammatical, whereas sentence (2) is ungrammatical. Both sentences contain two wh-phrases, "who" and "what," but only one wh-phrase can move to the specifier of CP in the main clause. The other wh-phrase must remain in situ (in its original position). Superiority dictates that the wh-phrase that is structurally higher in the base structure must move first. In the underlying structure of these sentences, "who" is the subject and is higher than "what," which is the object. Therefore, "who" must move to the specifier of CP, leaving "what" in situ.
Why does Superiority Matter?
The ungrammaticality of sentence (2) provides strong evidence for locality constraints. If movement were unconstrained, there would be no reason why "what" could not move to the specifier of CP. The fact that it cannot suggests that there is a rule or principle preventing it. This principle is related to the shortest move constraint or minimal link condition, which states that a constituent must move to the closest available position that satisfies its movement requirements. In this case, "who" is the closest wh-phrase to the specifier of CP, so it must move first. "What" cannot "skip over" "who" to move to the higher position. This violation of locality results in ungrammaticality. The superiority effect demonstrates that movement is not a free operation; it is governed by constraints that ensure constituents move locally. This constraint is not merely a stylistic preference; it is a fundamental aspect of English syntax, reflecting a deeper principle of how movement operates in human language.
Subject-Object Asymmetry
Another compelling piece of evidence for locality constraints comes from the subject-object asymmetry in wh-extraction. This asymmetry reveals that it is easier to extract wh-phrases from object positions than from subject positions. Consider the following examples:
- What did John buy?
- *Who did buy the book?
Sentence (1), where "what" is extracted from the object position, is perfectly grammatical. However, sentence (2), where "who" is extracted from the subject position, is significantly less acceptable, if not outright ungrammatical for many speakers. This contrast demonstrates that extraction from subject positions is somehow more constrained than extraction from object positions.
The ECP and Subject Extraction
One way to account for this asymmetry is through the Empty Category Principle (ECP), an older but still relevant concept in generative syntax. The ECP states that empty categories (traces left behind by movement) must be properly governed. Proper government can occur through head government (where the empty category is governed by a lexical head like a verb) or antecedent government (where the empty category is governed by its antecedent in a higher position). In object extraction, the trace left by the wh-phrase is head-governed by the verb. However, in subject extraction, the trace is not head-governed, and it must rely on antecedent government. The problem arises because the subject position is often shielded by an intervening barrier, such as the TP (Tense Phrase), making antecedent government more difficult. This difficulty in governing the trace in subject position leads to the ungrammaticality or marginality of subject extraction. More modern approaches might invoke phase theory, where the edge of a phase is more accessible for movement, and subject positions within a phase are less accessible until they move to the edge of the phase.
The Role of Barriers
The concept of barriers is crucial in understanding locality constraints. Barriers are syntactic nodes that block movement or government relations. When a wh-phrase tries to move across a barrier, the resulting sentence becomes ungrammatical. Subject positions often reside within barrier phrases, making their extraction more difficult. The subject-object asymmetry illustrates that movement is sensitive to the structural environment; constituents cannot simply move across any number of nodes. The presence of barriers forces movement to be local, adhering to a stepwise fashion that respects the hierarchical structure of the sentence. This stepwise movement, often referred to as cyclic movement, ensures that the moving constituent does not violate locality constraints by skipping over intervening phrases or barriers. This phenomenon provides compelling evidence that the human mind operates with a nuanced understanding of syntactic structure and its constraints on movement.
Implications for Linguistic Theory
The evidence from English, particularly superiority effects and the subject-object asymmetry, has profound implications for linguistic theory. These phenomena highlight that movement is not an arbitrary operation; it is governed by specific rules and constraints that reflect the underlying architecture of the language faculty. The existence of locality constraints suggests that the human mind employs a structured system for generating and interpreting sentences, a system that is sensitive to hierarchical structure and movement operations. These observations have led to the development of various theoretical frameworks aimed at capturing these constraints.
Minimalism and Locality
In the minimalist program, a dominant framework in contemporary generative linguistics, locality constraints are seen as a natural consequence of the principles of efficient computation. The minimalist program seeks to reduce linguistic theory to its bare essentials, assuming that the language faculty operates according to the simplest possible mechanisms. Movement, in this view, is driven by the need to check features, and it occurs in the most economical way possible. Locality constraints, such as the shortest move constraint, fall out from this drive for economy. The idea is that a constituent moves to the closest position where its features can be checked, minimizing the computational cost of movement. This approach elegantly accounts for locality effects, deriving them from more fundamental principles of linguistic computation. From a minimalist perspective, the superiority effect, for instance, is a direct result of the shortest move constraint, which dictates that the closest wh-phrase must move first, ensuring the most efficient derivation.
Phase Theory and Movement
Phase theory is another key component of modern generative syntax that directly addresses locality constraints. In phase theory, syntactic derivations proceed in phases, with CP and vP typically considered as phases. Each phase is a domain for syntactic operations, and movement is constrained to occur within a phase or to the edge of a phase. This phased movement ensures that constituents do not move arbitrarily far in a single step. When a constituent needs to move beyond a phase, it must first move to the edge of that phase, making it accessible for further movement in the next higher phase. This stepwise movement accounts for many locality effects, such as the superiority effect and the subject-object asymmetry. For example, in subject extraction, the subject might be located within a phase, making its extraction more difficult until it moves to the edge of the phase. Phase theory provides a sophisticated mechanism for capturing locality constraints, offering a detailed account of how movement is constrained within the hierarchical structure of the sentence. This framework aligns with the broader minimalist goal of deriving linguistic phenomena from fundamental principles, emphasizing the importance of locality in syntactic computation.
Conclusion
The evidence from English, particularly the superiority effects in multiple wh-questions and the subject-object asymmetry in wh-extraction, provides compelling support for the existence of locality constraints on movement. These constraints reveal that movement is not a free operation; it is governed by specific rules and principles that reflect the underlying architecture of the language faculty. Constituents move locally, adhering to a stepwise fashion that respects the hierarchical structure of the sentence. These observations have led to the development of theoretical frameworks, such as the minimalist program and phase theory, aimed at capturing these constraints. The minimalist program derives locality constraints from the principle of efficient computation, while phase theory offers a detailed account of how movement is constrained within phases. The ongoing exploration of locality constraints continues to deepen our understanding of the intricate mechanisms that govern human language, shedding light on the cognitive processes that underlie our linguistic competence. The simplest evidence from English serves as a crucial foundation for these theoretical advancements, highlighting the importance of empirical data in shaping our understanding of syntax and movement phenomena. Further research will undoubtedly uncover more nuanced aspects of locality constraints, providing a more comprehensive picture of the complex interplay between movement, structure, and meaning in natural language.