A reduced relative clause is a relative clause that is not marked by an explicit relative pronoun or complementizer such as who, which or that. An example is the clause I saw in the English sentence "This is the manI saw." Unreduced forms of this relative clause would be "This is the man that I saw." or "...whom I saw." Another form of reduced relative clause is the "reduced object passive relative clause", a type of nonfinite clause headed by a past participle, such as the clause found here in: "The animals found here can be dangerous." Reduced relative clauses are given to ambiguity or garden path effects, and have been a common topic of psycholinguistic study, especially in the field of sentence processing.
Finite types
Regular relative clauses are a class of dependent clause that usually modifies a noun. They are typically introduced by one of the relative pronounswho, whom, whose, what, or whichand, in English, by the wordthat, which may be analyzed either as a relative pronoun or as a relativizer ; see That a relativizer. Reduced relative clauses have no such relative pronoun or complementizer introducing them. The example below contrasts an English non-reduced relative clause and reduced relative clause. Because of the omission of function words, the use of reduced relative clauses, particularly when nested, can give rise to sentences which, while theoretically correct grammatically, are not readily parsed by listeners. A well-known example put forward by linguists is "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo", which contains the reduced relative clause Buffalo buffalo buffalo.
Non-finite types
In English, the similarity between the activepast tense form of verbs and the passive past tense can give rise to confusion concerning a special form of reduced relative clause, called the reduced object relative passive clause, the most famous example of which is
The horse raced past the barn fell.
In sentences such as this, when the reader or hearer encounters the verb he or she can interpret it in two different ways: as a main verb, or the first verb of a reduced relative clause. Linguist David W. Carrol gives the example of "the florist sent...", which could either go on to form a sentence such as "the florist sent the flowers to the elderly widow", or one such as "the florist sent the flowers was very pleased". Sentences like this often produce a garden path effect—an effect whereby a reader begins a sentence with one interpretation, and later is forced to backtrack and re-analyze the sentence's structure. The diagram below illustrates the garden path effect in the sentence "the florist sent the flowers was pleased," where represents the initial structure assigned to the sentence, represents the garden path effect elicited when the reader encounters "was" and has nowhere to put it, and represents the re-analysis of the sentence as containing a reduced relative clause. While reduced relative clauses are not the only structures that create garden path sentences in English, they are the "classic" example of garden path sentences, and have been the subject of the most research.
Use in psycholinguistic research
Across languages, reduced relative clauses often give rise to temporary ambiguity, since the first word of a reduced clause may initially be interpreted as part of the main clause. Therefore, reduced relative clauses have been the subject of "an enormous number of experiments" in psycholinguistics, especially for investigating whether semantic information or information from the context can affect how a reader or listener initially parses a sentence. For example, one study compared sentences in which the garden path effect was more likely because the reduced relative verb was one that was likely to be used as a main verb for its subject and sentences in which the garden path effect was less likely. Reduced relative clauses have also been used in studies of second-language acquisition, to compare how native speakers handled reduced relatives and how non-native speakers handle them. In languages with head-final relative clauses, such as Chinese, Japanese, and Turkish, non-reduced relative clauses may also cause temporary ambiguity because the complementizer does not precede the relative clause.
