In relative clause extraposition (RCE) in English, a noun is modified by a non-adjacent RC, resulting in a discontinuous dependency, as in: Three people arrived here yesterday who were from Chicago. Although discourse focus is known to influence the choice of RCE over truth-conditionally equivalent sentences with canonical structure (Rochemont and Culicover, English focus constructions and the theory of grammar, Cambridge University Press, 1990; Takami, A functional constraint on Extraposition from NP, John Benjamins, 1999), Hawkins (Efficiency and complexity in grammars, Oxford University Press, 2004) and Wasow (Postverbal behavior, CSLI Publications, 2002) have proposed in addition that RCE should be preferred when the relative clause is long (or ‘heavy’) relative to the VP because such structures are processed more efficiently in comprehension and production. The current study tested this hypothesis based on Hawkins' (Efficiency and complexity in grammars, Oxford University Press, 2004) domain minimization principles. In an acceptability judgment task, canonical sentences were rated significantly higher than extraposition sentences when the RC was light, but this difference disappeared when the RC was heavy. In a self-paced reading task, extraposition sentences were read significantly faster than canonical sentences when the RC was heavy, but there was no difference when the RC was light. In an analysis of RCE in the ICE-GB corpus, extraposed RCs were significantly longer than the VP on average, whereas canonical RCs were significantly shorter, and the proportion of sentences with extraposition decreased as the ratio of VP-to-RC length increased. These findings support Hawkins' (Efficiency and complexity in grammars, Oxford University Press, 2004) domain minimization principles and help explain why a discontinuous dependency is allowed and sometimes preferred even in a language with relatively fixed word order.
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