Blocking can be defined as the non-occurrence of some linguistic form, whose existence could be expected on general grounds, due to the existence of a rival form. *Oxes, for example, is blocked by oxen, *stealer by thief. Although blocking is closely associated with morphology, in reality the competing “forms” can not only be morphemes or words, but can also be syntactic units. In German, for example, the compound Rotwein ‘red wine’ blocks the phrasal unit *roter Wein (in the relevant sense), just as the phrasal unit rote Rübe ‘beetroot; lit. red beet’ blocks the compound *Rotrübe. In these examples, one crucial factor determining blocking is synonymy; speakers apparently have a deep-rooted presumption against synonyms. Whether homonymy can also lead to a similar avoidance strategy, is still controversial. But even if homonymy blocking exists, it certainly is much less systematic than synonymy blocking.
In all the examples mentioned above, it is a word stored in the mental lexicon that blocks a rival formation. However, besides such cases of lexical blocking, one can observe blocking among productive patterns. Dutch has three suffixes for deriving agent nouns from verbal bases, -er, -der, and -aar. Of these three suffixes, the first one is the default choice, while -der and -aar are chosen in very specific phonological environments: as Geert Booij describes in The Morphology of Dutch (2002), “the suffix -aar occurs after stems ending in a coronal sonorant consonant preceded by schwa, and -der occurs after stems ending in /r/” (p. 122). Contrary to lexical blocking, the effect of this kind of pattern blocking does not depend on words stored in the mental lexicon and their token frequency but on abstract features (in the case at hand, phonological features).
Blocking was first recognized by the Indian grammarian Pāṇini in the 5th or 4th century
Jane Chandlee and Jeffrey Heinz
Computational phonology studies the nature of the computations necessary and sufficient for characterizing phonological knowledge. As a field it is informed by the theories of computation and phonology.
The computational nature of phonological knowledge is important because at a fundamental level it is about the psychological nature of memory as it pertains to phonological knowledge. Different types of phonological knowledge can be characterized as computational problems, and the solutions to these problems reveal their computational nature. In contrast to syntactic knowledge, there is clear evidence that phonological knowledge is computationally bounded to the so-called regular classes of sets and relations. These classes have multiple mathematical characterizations in terms of logic, automata, and algebra with significant implications for the nature of memory. In fact, there is evidence that phonological knowledge is bounded by particular subregular classes, with more restrictive logical, automata-theoretic, and algebraic characterizations, and thus by weaker models of memory.
Phenomena involving the displacement of syntactic units are widespread in human languages. The term displacement refers here to a dependency relation whereby a given syntactic constituent is interpreted simultaneously in two different positions. Only one position is pronounced, in general the hierarchically higher one in the syntactic structure. Consider a wh-question like (1) in English:
(1) Whom did you give the book to <whom>
The phrase containing the interrogative wh-word is located at the beginning of the clause, and this guarantees that the clause is interpreted as a question about this phrase; at the same time, whom is interpreted as part of the argument structure of the verb give (the copy, in <> brackets). In current terms, inspired by minimalist developments in generative syntax, the phrase whom is first merged as (one of) the complement(s) of give (External Merge) and then re-merged (Internal Merge, i.e., movement) in the appropriate position in the left periphery of the clause. This peripheral area of the clause hosts operator-type constituents, among which interrogative ones (yielding the relevant interpretation: for which x, you gave a book to x, for sentence 1). Scope-discourse phenomena—such as, e.g., the raising of a question as in (1), the focalization of one constituent as in TO JOHN I gave the book (not to Mary)—have the effect that an argument of the verb is fronted in the left periphery of the clause rather than filling its clause internal complement position, whence the term displacement. Displacement can be to a position relatively close to the one of first merge (the copy), or else it can be to a position farther away. In the latter case, the relevant dependency becomes more long-distance than in (1), as in (2)a and even more so (2)b:
a Whom did Mary expect [that you would give the book to<whom >]
b Whom do you think [that Mary expected [that you would give the book to <whom >]]
50 years or so of investigation on locality in formal generative syntax have shown that, despite its potentially very distant realization, syntactic displacement is in fact a local process. The audible position in which a moved constituent is pronounced and the position of its copy inside the clause can be far from each other. However, the long-distance dependency is split into steps through iterated applications of short movements, so that any dependency holding between two occurrences of the same constituent is in fact very local. Furthermore, there are syntactic domains that resist movement out of them, traditionally referred to as islands. Locality is a core concept of syntactic computations. Syntactic locality requires that syntactic computations apply within small domains (cyclic domains), possibly in the mentioned iterated way (successive cyclicity), currently rethought of in terms of Phase theory. Furthermore, in the Relativized Minimality tradition, syntactic locality requires that, given X . . . Z . . . Y, the dependency between the relevant constituent in its target position X and its first merge position Y should not be interrupted by any constituent Z which is similar to X in relevant formal features and thus intervenes, blocking the relation between X and Y. Intervention locality has also been shown to allow for an explicit characterization of aspects of children’s linguistic development in their capacity to compute complex object dependencies (also relevant in different impaired populations).