Fonetische correlaten en communicatieve functies van linguïstische structuu

Caspers, J.

The present paper reports on an investigation of Dutch Map Task dialogues, looking for specific melodic turn-keeping cues. The materials were divided into so-called Inter Pausal Units (cf. [1]), and all IPU boundaries were labeled as instanc-es of either turn-keeping or turn-changing. The pitch accents and boundary tones preceding the IPU boundaries were labeled in the ToDI system [2]. Results indicate one particular melodic configuration that seems typically associated with turn-keeping: an accent-lending rise followed by level high pitch (H * %). But also the level boundary tone (%) in itself and – to a lesser extent – the rising pitch accent (H*) seem to function as melodic turn-keeping cues. 1

Johanneke Caspers

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Pitch accents, boundary tones and turntaking in Dutch Map Task dialogues

Leiden University Scholary Publications

PITCH ACCENTS, BOUNDARY TONES AND TURN-TAKING IN DUTCHMAP TASK DIALOGUESJohanneke CaspersPhonetics Laboratory/Holland Institute of Generative LinguisticsPO Box 9515, 2300 RA Leiden, The Netherlands; CASPERS@RULLET.LEIDENUNIV.NLABSTRACTThe present paper reports on an investigation of Dutch MapTask dialogues, looking for specific melodic turn-keepingcues. The materials were divided into so-called Inter PausalUnits (cf. [1]), and all IPU boundaries were labeled as instanc-es of either turn-keeping or turn-changing. The pitch accentsand boundary tones preceding the IPU boundaries werelabeled in the ToDI system [2]. Results indicate one particularmelodic configuration that seems typically associated withturn-keeping: an accent-lending rise followed by level highpitch (H* %). But also the level boundary tone (%) in itselfand – to a lesser extent – the rising pitch accent (H*) seem tofunction as melodic turn-keeping cues.1. INTRODUCTIONThe alternation of speaking turns in every-day conversation issurprisingly smooth (generally one speaker at a time) and veryfast (often no pause between successive speakers), which maybe explained only in terms of a highly complex system ofinteracting factors, comprising syntax, semantics, pragmatics,prosody, visual cues etc. The relevance of intonation for theturn-taking process is recognized, but the knowledge of itsprecise function in the structuring of conversation is still fairlylimited. The question asked in the present investigation iswhether specific pitch accent types and/or boundary tone typesfunction as turn-keeping cues in Dutch dialogue. To answerthis question a corpus of Map Task dialogues (task-orientedspontaneous dialogues) was analyzed.Within the so-called Conversation Analysis, the turn-takingmechanism is approached as a system of rules adhered to bythe interlocutors. Sacks, Schegloff and Jefferson [3] set out thelines along which numerous empirical studies of naturalconversation have been carried out, using detailed transcriptsof natural conversation as a tool for finding out more aboutthe systematics of conversational interaction. A central notionis the ‘Transition Relevant Place’, a point of possible comple-tion of the present turn, where turn-taking becomes relevant(but not obligatory). Interlocutors project these points ofpossible turn completion before their actual occurrence –hence the often jointless transition between consecutive speak-ers – and my interest is in the role intonation may play in thisprojection of upcoming turn endings. Only recently, CA hastaken an interest in speech melody as a factor in the organiza-tion of conversation (e.g. [4,5,6,7,8]). Note that the CA studiesare qualitative in nature, which means that no frequencycounts are given for specific variables, and that data arepresented in the form of detailed examples.There is some evidence from the analysis of natural dialoguethat pitch accents play a significant role in the projection ofpossible turn endings ([7,8] for German and English respec-tively). It seems that the shape of a potentially final pitchaccent (plus the non-prominent tones that follow) can signalwhether the current speaker wants to continue speaking orgive the floor to someone else.Furthermore, perception experiments [9] provided evidence forthe relevance of a certain melodic configuration for the turn-taking system in Dutch. In these experiments an accent-lend-ing rise followed by level pitch up to the end of the utterance(H* %) was compared to an accent-lending rise followed by afinal rise (H* H%). Below stylized versions of the two con-tours are given on a short utterance (a proper name; thestressed syllable is capitalized), annotated in the ToDI system(‘Transcription of Dutch Intonation’, cf. [2]):_________/1. Jan-WILlemH* %____/____/2. Jan-WILlemH* H%The contours were presented in controlled environments, inwhich listeners were asked to perform a number of compari-son and rating tasks. The results indicated that H* % cannotreadily be interpreted as a signal that the listener should takethe next turn. Instead, use of this contour was understood as asign that the current speaker wanted to keep the turn. Thecontour ending in a final rise (H* H%) was interpreted aseither turn-keeping or turn-yielding (for more details see [9]).These findings led to the following research questions. Doesan accent-lending rise followed by level high pitch (H* %)function as a turn-holding cue in natural Dutch dialogue? Arethere other melodic configurations with the same function?2. APPROACHA quantitative analysis of the melodic and turn-transitionalstructures of natural conversations should provide some insightinto the role that intonation plays in the turn-taking system. Inorder to find out whether a systematic relationship exists be-tween speech melody and turn-taking, we need to locatepossible turn transition places in the dialogue, and then exam-ine these places for the transition type actually occurring andthe melodic characteristics immediately preceding these posi-tions. I adopt the approach taken by Koiso et al. [1] who useso-calledInter Pausal Units (IPUs) to divide spontaneous dia-logues into turn-relevant components. IPUs can be determinedobjectively and the boundaries between these units can belabeled as instances of either turn-holding or turn-changing.The accent-lending and boundary-marking configurationspreceding every IPU boundary were described in terms of theToDI model. After these labeling stages, the available datawere viewed in the light of the research questions posed.3. MATERIALSUse was made of a corpus of Dutch guided spontaneousconversations, so-called Map Task dialogues (cf. [10]). Inthese task-oriented dialogues, maps provide a handle on anessentially spontaneous conversation. Two roles can be distin-guished: an‘instruction giver’ and an ‘instruction follower’.The former participant has a map with a route drawn on it ands/he has to explain to the instruction follower which route todraw on his or her unmarked copy of the map. The partici-pants cannot see each other’s maps. Both maps have a numberof reference points on it (e.g.,‘old pond’, ‘new pond’, ‘greenmeadow’) and by introducing small differences between thesereference points it is possible to complicate the dialogue tosome extent. The materials used for the present investigationwere collected by Bob Ladd and Astrid Schepman.4. ANALYSIS4.1. Inter Pausal UnitsThe materials were divided intoInter Pausal Units. An IPU isdefined as "a stretch of a single speaker’s speech bounded bypauses longer than 100 ms" ([1], p. 299). This means thatboundaries were drawn in all positions where a pause longerthan 100 ms appeared in the signal, and in positions where achange of speaker occurred. In contrast with [1], overlappingstretches of speech were included in the analysis.4.2. Transition typesAll IPU boundaries were characterized with respect to turn-transition type. A division was made between the categoriesturn-holding and turn-changing: the former meaning that thesame speaker continues after a (turn-internal) pause of 100 msor more, or after a backchannel uttered by the listener (a shortoptional utterance like‘uh-huh’), the latter indicating that aturn change has occurred (i.e., the current listener takes thenext turn). Interruptions were categorized as instances of turn-keeping, since the interrupted speakerintended to keep his orher turn. For more details the reader is referred to [11].4.3. Melodic CharacteristicsThe third stage of the analysis comprised a transcription of themelodic phenomena occurring immediately before each IPUboundary. As a tool for labeling the melodic phenomena, therecently developed ToDI system was chosen. Starting from theprinciple that the "potential last accent" (cf. [7]) is of majorimportance to the turn-taking system, the last pitch accentbefore every IPU boundary was transcribed, as well as thetone sequence following this accent up to the boundary. Theintonation was labeled on the basis of the auditory impressionof the pitch curve only. Before every IPU boundary a bound-ary tone was transcribed, which means that intonation domainboundaries were determined by pauses or speaker changesactually occurring in the material, and not by the syntacticstructure of the utterance. Note that, as a result, the boundarytones marked in the current analysis do not necessarily corre-spond to the boundary tones as defined by ToDI.5. RESULTSI total, eight complete Map Task dialogues were analyzed,amounting to over 40 minutes of speech. These materialscontained 1552 IPU boundaries. It was hypothesized that anaccent-lending rise followed by a level high tone (H* %)would predominantly be followed by a turn from the samespeaker. Table 1 presents the frequency of turn-changingversus turn-holding transitions immediately following the H*% configurations found in the materials (N=140).Table 1: Absolute (and relative) frequency of turn-changing(+CHANGE) and turn-holding transitions (−CHANGE) after H*%.IPU transition type frequency+ CHANGE 19 (14%)− CHANGE 121 (86%)total 140 (100%)The table shows that in 86% of the cases the configuration H*% is followed by an utterance by the same speaker(−CHANGE), which confirms the turn-holding character hypoth-esized of this melodic configuration. However, the amount ofavailable data is relatively small, since only 140 of the 1552IPU boundaries analyzed were preceded by H* % (9%). Thefact that there is no clear boundary tone in the H* % configu-ration – the pitch remains flat until the following IPU bound-ary and does not drop to a clear low point (L%) or rise to ahigh point (H%) on the final syllable – may be crucial to theissue of turn-taking. In the ToDI system, nuclear contoursending in % are described as "half-completed", clearly point-ing to the unfinished nature of such melodic configurations.The following question then presented itself: doall configu-rations ending in % generally function as turn-holding cues?Table 2 presents the number of turn-changing and turn-holdingtransitions broken down by boundary tone type. Note that thematerials contained 94 cases that could not be transcribed(labeled "?"), partly due to considerable overlap in speech.Results show that in the majority of cases an IPU boundaryTable 2: Absolute (and relative) frequency of turn-changing transitions (+CHANGE) versus turn-holding transitions (−CHANGE) pertype of preceding boundary tone; grey cells contain the data for the level boundary tones (%).IPU transition typepreceding boundary tone type + CHANGE − CHANGE totalL% 275 (54%) 234 (46%) 509H% 254 (45%) 315 (55%) 569% 58 (15%) 322 (85%) 380? 37 (39%) 57 (61%) 94total 624 (40%) 928 (60%) 1552was preceded by a low (N=509) or high (N=569) boundarytone. After an L% boundary tone the turn changes in 54% ofthe cases, and after a H% boundary tone the current speakerkeeps the turn in 55% of the cases. IPU boundaries that arepreceded by level non-low pitch (%, N=380) are followed bya transition that can be interpreted as turn-keeping in 85% ofthe cases (i.e., the current speaker continues after a pause, thecurrent listener backchannels, or the current speaker is inter-rupted). A post-hoc analysis indicates that the percentage ofturn-keeping transitions differs significantly for all threeboundary tones: after L% there is a tendency to change theturn and after H% to hold the turn, but after % the effect ismuch more outspoken: in most cases the turn stays with thecurrent speaker.The results for the % boundary tone closely resemble thosefound for the H* % configuration as a whole (cf. table 1);does this mean that the pitch accent type preceding the %boundary tone is irrelevant? Table 3 gives the frequency ofturn-keeping and turn-changing transitions broken down by thedifferent pitch accent types. Since a number of IPUs containeda boundary tone but no pitch accent – the majority of thesecases constitute a filled pause (‘uhm’ ), or function as a back-channel (cf. [12]) – the total number of cases in table 3 isconsiderably lower than in table 2.Averaging over boundary tone types, a rising pitch accent(H*) is followed by an utterance from the same speaker in74% of the cases, whereas H*L and L*(H) accents are fol-lowed by a change of speaker in roughly half of the cases. Apost-hoc analysis reveals that the H* pitch accent is followedby a significantly higher percentage of turn-keeping transitionsthan each of the other three types of pitch accents; there wereno further differences. Limiting the dataset to the IPUs thatcontain a – transcribable – pitch accent as well as a boundarytone, ANOVA shows main effects of boundary tone type(F(2,1081)= 40.36, p<.001) and pitch accent type (F(3,1080)= 3.46,p<.05) on the percentage of following turn-keeping transitions,as well as a significant interaction (F(6,1072)= 4.51, p<.01). Thismeans that, in addition to a large effect of boundary tone typeand a much smaller effect of pitch accent type, there is acombined influence of both tone types on the chances for turn-keeping at the following IPU boundary. For lack of space thisissue will not be further elaborated upon here.So far, the available data present no clearly turn-yieldingmelodic configurations.6. CONCLUSION AND DISCUSSIONThe data presented in section 5 provide support for the hy-pothesis that an accent-lending rise followed by level pitch(H* %) functions as a turn-keeping cue in Dutch spontaneousdialogues. Furthermore, the data show that when there is noclear boundary tone immediately before an IPU boundary,there is no subsequent speaker change in approximately 85%of the cases, in contrast with low or high boundary tones,which are followed by a turn change in roughly half of thecases. The results indicate that the absence of a clear boundarytone is generally taken as a sign that the current speaker hasnot finished yet (and wants to continue).The findings are in concurrence with results presented in [9],where an accent-lending rise followed by a high boundarytone (H* H%) was found to be ambiguous between turn-keep-ing and turn-yielding, whereas an accent-lending rise followedby level pitch (H* %) was interpreted by subjects as a signalfor turn-keeping. The findings also support the intuition of [7]and [9] that intonation does not seem to play an unequivocalrole in yielding the turn (in German and Dutch respectively),whereas there does seem to be evidence for the existence ofmelodic turn-keeping cues.In their paper presenting a qualitative analysis of BritishEnglish conversation, [8] conclude that there are specific"TRP-projecting accents" – pitch accents that project a Transi-tion Relevant Place – as well as specific non-TRP-projectingaccents. The current findings indicate that Dutch also has anon-TRP-projecting accent, but the data present no evidencefor the existence of specific TRP-projecting configurations.Further quantitative research is needed to determine whetherTable 3: Absolute (and relative) frequency of turn-changing transitions (+CHANGE) versus turn-holding transitions (−CHANGE) pertype of preceding pitch accent; grey cells contain the data for the rising pitch accents (H*).IPU transition typepreceding pitch accent type + CHANGE − CHANGE totalH* 64 (26%) 186 (74%) 250H*L 392 (52%) 365 (48%) 757L* 11 (61%) 7 (39%) 18L*H 34 (53%) 30 (47%) 64? 43 (43%) 58 (57%) 101total 544 (46%) 646 (54%) 1190English differs from Dutch and German in the presence versusabsence of specific melodic configurations that project anupcoming change of speaker, or whether English exploitsmelodic turn-holding devices but no unique melodic turn-yielding cues, as seems to be the case in Dutch and German.7. ACKNOWLEDGMENTSThis research was funded by the Netherlands Organization forScientific Research (NWO) under project #355-75-002.8. REFERENCES1. Koiso, H., Horiuchi, Y., Tutiya, S., Ichikawa, A., andDen, Y., “An analysis of turn-taking and backchannelsbased on prosodic and syntactic features in JapaneseMap Task dialogs” , Language and Speech 41, 295-321,1998.2. Gussenhoven, C., Rietveld, T. and Terken, J., “ToDI,Transcription of Dutch Intonation” , URLhttp://lands.let.kun.nl/todi/, 1999.3. Sacks, H., Schegloff, E.A., and Jefferson, G., “A sim-plest systematics for the organization of turn-taking forconversation” , Language 50, 696-735, 1974.4. Auer, P., “On the prosody and syntax of turn-continu-ations” , in E. Couper-Kuhlen and M. Selting (eds),Prosody in conversation, Cambridge University Press,Cambridge, 57-100, 1996.5. Couper-Kuhlen, E., “ Intonation and clause combining indiscourse: the case of ‘because’” , Pragmatics 6,389-426, 1996.6. Ford, C.E., and Thompson, S.A., “ Interactional units inconversation: syntactic, intonational, and pragmaticresources for the management of turns” , in E. Ochs,E.A. Schegloff and S.A. Thompson (eds), Interactionand grammar, Cambridge University Press, Cambridge,134-184, 1996.7. Selting, M., “On the interplay of syntax and prosody inthe constitution of turn-constructional units and turns inconversation” , Pragmatics 6, 357-388, 1996.8. Wells, B., and Macfarlane, S., “Prosody as an interac-tional resource: turn-projection and overlap” , Languageand Speech 41, 265-294, 1998.9. Caspers, J., “Who’s next? The melodic marking ofquestion versus continuation in Dutch” , Language andSpeech 41, 375-398, 1998.10. Anderson, A.H., Bader, M., Gurman Bard, E., Boyle,E., Doherty, G., Garrod, S., Isard, S., Kowtko, J.,McAllister, J., Miller, J., Sotillo, C., and Thompson,H.S., “The HCRC Map Task Corpus” , Language andSpeech 34, 351-366, 1991.11. Caspers, J., “Looking for melodic turn-holding configu-rations in Dutch” , in H. de Hoop and T. van der Wou-den (eds), Linguistics in the Netherlands 2000, JohnBenjamins, Amsterdam, to appear.12. Caspers, J., “Melodic characteristics of backchannels inDutch spontaneous dialogues” , Proceedings of the 6thInternational Conference on Spoken Language Pro-cessing, [this volume], 2000.

Pitch accents, boundary tones and turn-taking in Dutch Map Task dialogues

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Pitch accents, boundary tones and turn-taking in Dutch Map Task dialogues

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