「インタラクション，97」 平成9年2月

AResponsiveDialogSystem

NigelWardandⅥねtaruTsukaharal
UniversityofTokyo
Beingresponsiveisimportantindialog．In particlilar，back−Channelfeedbackisessential
tohumanconversations．Back−Cllannelfbedbackissometimesproducedwitho11tthillking，

inresponsetosimpleprosodicclues．AsimpleimplementationofthisbellaViorproduces
naturalresponsesinconversationwithlivellumanSubjects．

あいづちを打てる対話システム
N．ワード
塚原渉
東京大学

対話においては応答性が重要である。なかでも、なものである。あいづちを含む会話の分析から、あいづちは人間同士の会話にとって必要不可欠しばしば内容ではなく、簡単な韻律的特徴に反この特徴を組み込んだシステムは、実際の人間応してあいづちが打たれていることが分かった。との会話で自然な応答をすることができた。

1 Motivationtheseabilitiesascentral，andbuildsystemsaroulld

them．Thispaperreportsonalleffortin．thelatterdirection．
an elusive goal．Today，thanks to advance＄in Our currellt WOrkfocuses ollpOilltS2alld3
SPeeCh recognition，dialog−Capable systems exist，
above，undertherubricof respollSivenessindia−
but they can notyetinteract natural1ywithlm−
log，，．（Thisisprerequisitetopointl，tOtlleCXtent

Modelinglanguage as people real1y u＄eitismans．A broad−brushlist of weaknesses of thethat pragmaticinformationis oftelleXpreSSCdiIl

typicalspeechsystemoftoday showswheremoretheinteractionmorethaninthewords．Thismay

workisneeded：also providealleWangleofattackonpoint4，inthatitopensupthepossibilityofmulti−mOdalsys−

1．Theinformation conveyedis propositionaltems based onsubsumption architectures（Ward（forexample，aSpeCi丘cationofthefieldsofa1996a）．）
databa5equery）；

blltforhumandialog，infbrmationexchange
atpragmaticandotherlevelsisalsoimpor−

2 Phenomenon

tant．

Back−Cllannelfbedbackisproducedbyonepar−

2．Priorityis glVen tO11nderstanding and re−

SpOnSlngaCCurately；
butforhumandialog，beingresponsiveandinteractiveisalsoimportant．

ticipantinresponseto＄OmeutteranCebytlleO・ther
Participant．Prototypicalback−Channelfeedback：1．encouragesorallowstheothertokeepspeak−
1ng，2．showsattentionandinterest，3，Showsun−

d声rStandingand／oragreement・（DiscussionQfour
exact，definitionappearselsewhere（Ward1996b）・
3．ThegranularityofinteractionistlleSentenCe；
InEnglishmmanduhhuharetypicalback−Channel
but fbr hllman dialog，interaction happens
fbedback．InJapaneSetheaizuclliunismosttypi−
freq11ently，ln real一tilne，Oftenwith overlap−
cd．
Plnguttera皿CeS；

3 Analysis
4．Thesystemcanonlyunderstandword＄，alld
Can、0nly＜producewords；
MaiiyllaVeSOughtforthepcrceptualcluethat

butforhumandialog，Otherchannelsofcom−
tells訂Participant it snowtimetoproduceback−munication，includingeyecontact，geStureS，
chanllelfbedback ．It hasoft611been speculated
andprosody，arealsopresellt・tllatthisclue缶01nthespeakerwouldbeprosodic，

ratllerthaninvoIvingmeanlng．

Given that the＄e pOints areimportant to hu−
Welookeda．tthe prosodicenvironmentsof900
manlang11ageuSe，thequestionarises：howdowe
aizuchiinllaturalJapaneseconversatioll．Potentialbuild systems with these abilities？The，Obvious
cl11eSWeCOnSideredincludedpitchcontours，VOWe1
approachis to add these abilities to a typical
1engtheningorspeakingrateslowdown，VOlumeill−
SpeeChsystem．Analternativeapproachistotake
crease or decrease on負nalsyllables，alow pitch
1Mechano−InformaticEngineerlnglUniversityofTokyoI
point，and grossenergylcvelcllangeS（to detcct7−3−11Iongo，Bunkyo−ku，Tokyol13Japan；＋8ト3−3182− whentlleSPeakerfinishesspeaking），aSSuggeSted
2111ext． 6282；fax：＋81−3−3815−8356；（nigel，tSuka）
intheliterature（＄eeCitationsin（Ward1996b））・◎sanpo．t．u−tOkyo．ac．jp；http：／／www．sanpo・t．u−tOkyo・aC・jp／

Noneofthe＄eappearedtohaveastrongcorrelatioIl（〜migel／，〜tSuka／index−jl−59−Upondetectionof

areglOnOfpitcl11essthanthe30tlトperCentilepitchleveland
COntinulngforatleast150ms，COmlngafteratleast700msofspeech，
you＄houldproduceanaizuclli300mslater，
PrOVidingyouhavenotdonesowithintheprecedingl．Oseconds．

図1：Back−ChannelFeedbackR11le
Withwhetherback−Channelfeedbackwa5prOduced
Or nOt．
However，there wasonegood clue：areg10n Of

lowpitch．Thiscorrelationcanbeopera−tionalized
a＄thepredictionruleseeninFigurel．

Itiscommonlythoughtthatsilence（attheelld

Ofaspeaker sturn）isamajorclueforback−ChanTelfeedback．Thiswasnotthe caseforourdata；ln−deeditcouldnotbe，glVentheswiftne＄SOfback−channelfbedbackand the slowne＄SOfh11manreaC−tion time．It t11rnS Out that the aboveru1e han−dles both back−Channelfeedbackwhich waBprO−
ducedafterthespeakerpausedand＄tOPPed，and

thatwhichoverlappedthespeaker scontinuedut−
terance．

図2：ExperimentSet−up

4．Results
We tested the predictions of the above rule

recognitionorunderstanding．

against the corpu＄Ofhllman COnVerSations．We Itissometimesassumed thatreal−timerespon−

observedacoverageof50％atanaccuracyof34％，
Sivenessinspokendialogsystemsismerelyaques−
OVerallspeakersand王山dialogtypes．Forsomesit−
tionoffastalgorithms andfast hardware・HereuationsperformanCeWaSVerygOOd：inparticular，We Seethat thatisnot tlleWholestory：thereis
COmparCdtotlleOCCurrenCeSOfai2；uChisprod11Cedalsothelmman−factorsissueofexa．ctlyhowtotime
byJHinresponsetoⅨIintheir5minuteconver−
feedback．Ourdata8uggeStthattllisshouldbenei一Sation，therulecorrectlypredicted69％（54／78），
七bertoofa5tnOrtOOSlow．

withanaccuracyof68％（54correctpredictions／Ournextstepwillbetointegratethisnewre−
81totalpredictions）．
Wbalsohavetestedtheperfbrmanceoftherule
inliveconversation．

SpOnSivenesswithextanttechniquesforrecognition

andundersta皿ding；Ouraimwillbetobuildasys−temthatwillinteracttrulynat11ral1ywithpeople

Inordertogetpeopletotrytointeractnaturally

inasimpleverbalgame．

withthesystem，itwaBneCeSSarytOfooltheminto

thinkingthattheywerei雨eractingwit11Aperson・

6 Acknowledgements

Soweuseda．humandecoytostart・theconversa−
tion，andthenletthesy＄temta．keover．
WethankⅨeikichiHiroseforthepitchtracker，We have done experiments over the telephone

JojiⅡabuforllelping負gureouthowtofo01sub−andinthelal）OratOry，Withapartitionsothatthejects，andseveraldozenstudentsforconversations
Subject couldn，t see whenit the wa5the sy＄tem
andlabeling．
thatwaLSreSpOnding（Figure2）．Inbothca5eSthe
SyStem sresponsesseemnatural．

Re鮎rences

Itisint

back−Channelfbedba．ckisnotdetectedbymo8tSub−
Ⅵbrd，Nigel（1996a）．ReactiveResponsivenessin
jects；theysti11thinktheyaretalkingtoahuman．
Dialog．InAAAJ凡才J∫ymj川β査≠打10几β〝加died
Thedi庁erencei＄，however，VeryObviollStOOthers
Co9nilionandAction，pp．129−133．American
listeningtotheconversation．

AssociationforArtificialInte11igence．

Essential1ythe same predictionru1egave goodperformanceforsomeEnglishspeakersinliveex−
periments．

Ward，Nigel（1996b）．UsingProsodicCluestoDe−cide When to Produce Back−Chan11elUtter−
ances．InJタタβ血ねγ几α如几αJCo可ereれCe Oれ
ざpoたeれエα†岬≠叩eProceββ血タ，pp．1728−1731．

5 Significance
Wehavedemonstrated asystemthatcankecp
upitsendofaconversation，Withoutdoingspeech
ー60−