https://doi.org/10.1177/0023830916665653 Language and Speech Language and Speech 2017, Vol. 60(4) 505–529 © The Author(s) 2016 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0023830916665653 journals.sagepub.com/home/las Phrase Lengths and the Perceived Informativeness of Prosodic Cues in Turkish Nazik Dinçtopal Deniz Boğaziçi University, Turkey Janet Dean Fodor The City University of New York, USA Abstract It is known from previous studies that in many cases (though not all) the prosodic properties of a spoken utterance reflect aspects of its syntactic structure, and also that in many cases (though not all) listeners can benefit from these prosodic cues. A novel contribution to this literature is the Rational Speaker Hypothesis (RSH), proposed by Clifton, Carlson and Frazier. The RSH maintains that listeners are sensitive to possible reasons for why a speaker might introduce a prosodic break: “listeners treat a prosodic boundary as more informative about the syntax when it flanks short constituents than when it flanks longer constituents,” because in the latter case the speaker might have been motivated solely by consideration of optimal phrase lengths. This would effectively reduce the cue value of an appropriately placed prosodic boundary. We present additional evidence for the RSH from Turkish, a language typologically different from English. In addition, our study shows for the first time that the RSH also applies to a prosodic break which conflicts with the syntactic structure, reducing its perceived cue strength if it might have been motivated by length considerations. In this case, the RSH effect is beneficial. Finally, the Turkish data show that prosody- based explanations for parsing preferences such as the RSH do not take the place of traditional syntax-sensitive parsing strategies such as Late Closure. The two sources of guidance co-exist; both are used when available. Keywords Sentence processing, prosodic phrasing, Turkish, Late Closure, Rational Speaker Hypothesis 1 Introduction Since the classic study by Lehiste (1973), a growing number of experiments have demonstrated that the prosody of an utterance can provide listeners with cues to its syntactic structure (e.g., Corresponding author: Nazik Dinçtopal Deniz, Boğaziçi University, Faculty of Education, Department of Foreign Language Education, Bebek, 34342, Istanbul, Turkey. Email: nazik.dinctopal@boun.edu.tr 665653LAS 0 0 10.1177/0023830916665653Language and SpeechDeniz and Fodor research-article 2016 Article