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<Paper uid="C00-2107">
  <Title>Realizing Expressions of Doubt in Collaborative Dialogue *</Title>
  <Section position="4" start_page="740" end_page="743" type="metho">
    <SectionTitle>
3 Communicating an Expression of
</SectionTitle>
    <Paragraph position="0"/>
    <Section position="1" start_page="740" end_page="740" type="sub_section">
      <SectionTitle>
Doubt
</SectionTitle>
      <Paragraph position="0"> We assume appropriate mechmfisms for detecting conflict and determining when to engage in a sub-dialogue by expressing doul)t(Chu-Carroll and Carberry, 1998), as well as an approi)riate belief revision mechmfism, and in this paper concentrate on how an expression of doubt should be realized as an utteranee. A cooperative agent should be as informative as ne.eded, without expressing too much irreleva.nt intbnnation(Grice, 1975). Thus, in formulating an expression of doubt, we must consider how much the doubted ageut needs to know in order to collaborate in resolving the doubt and how much we can expect him to infer without being exl)lieitly told. In addition, Clark (1.996) argues that particiI)ants in discourse select; utterances that express their eommuni(:ative intent efficiently, oft, ca in sentence flagmeats. Since such efficiency of ezpression is the expected natural form of discourse, a hearer is likely to (terive unintended imt)lications from significantly less economical realizations.</Paragraph>
      <Paragraph position="1"> Expressions of doubt, by our detinition, signal nonacceptance because of 'unccrl, ain disbelief. In order for the doubted agent to attemt)t to collaborate in resolving the doubt, he needs to know several things. Most basically, he nee(is to recognize that there is doubt in a particular utterance. In the absence of an objection to an utterance, the speaker will assmne an implicit acceptance(Lmnbert and Carberry, 1999). To efficiently negotiate an acceptable resolution to the belief conflict, ideally the doubted agent must know something about the 1)ellen of the doubtiug agent; in particular, which belief(s) are causing her nonacceptance, and the strength of these beliefS. If the doubted agent decides to retain his original beliet:s, this information helps him to construct an argument that will be maximally effective and efficient in his attempt to convince the doubting agent(Chu-Carroll and Carberry, 1998).</Paragraph>
      <Paragraph position="2"> To i(lentifs~ how expressions of (loubt are realized in naturally occurring dialogue and how tiles(; realizations convey the requisite beliet's, we analyzed features of individual ext)ressions of doubt extracted from natural corpora, and correlated the various forms of the utterances with the features of the underlying beliefs, t{owever, as explained ill Section 3.3, the use of machine learning techniques was not apt)ropriate due to the nature of our corpus. Section 3.1 discusses features of underlying beliefs and Section 3.2 discusses the various forms that an expression of doubt can take. Section 3.3 then presents it set of rules that relate the two.</Paragraph>
    </Section>
    <Section position="2" start_page="740" end_page="742" type="sub_section">
      <SectionTitle>
3.1 Belief features
</SectionTitle>
      <Paragraph position="0"> As noted above, beliefs play a prominent role in expressions of doubt, since a speaker will ideally convey enough intbrmation tbr the hearer to diseern 1) that she is expressing doubt, 2) what she is doubting, 3) any support she has tbr the doubt, and 4) the strength of this supi)ort. In addition, speakers tend to differentiate new SUl)porting int'ornlalion from that which is already part of the COlIlliIOU ground aud which should already have been considered. These beliefs are often IIot explicitly stated, but are assumed to be inferable by the doubted agent based on his knowledge of the previous dialogue, knowledge of the other agent's belieN, a model of stereotypical beliefs, linguistic knowledge, and the particular realization of the doubting agent's utteralice. null For example, consider the following assertion and two possible responses, each expressing doubt at; the prot)osition P, to~,a that John Smith gets $800 a month fl'om Social Seeurityd: S: ,loh, n Smith, (lets $800 a month in Social Security.  1) U: Isn't h,e less th, an 62 yem's old? 2) U: $800'?  In 1) U relies on illutua,1 donmin knowh:dge to express (hml)t at Pdo,,bt by contending some ()tiler proposition Pi that implies -,P, to~,bt(Lamllert and Carberry, 1999), namely that Slnith is younger than 62. In the rest of this paper, P, to,,a refers to the doubted proposition and Pi to a proposition other than Pao,,bt, if any, that is the reason for this doubt. In addition, expectations also play a role in expressions of doubt. In the simplest case, the violated expectation is just that I~to~,bt is fiflse. In other situations, an agent may have an expectation that a proposition will be false if instmltiated with some particular subset of its possible instantiations. Responses that conflict with these expectations may provoke an expression of doubt, even though the doubting agent may have little or no support for the ext)ectation. Such violated expectations are oftel1 signaled by elliptical fragments, such as response 2) above where U conveys not oIfly that she doesn't  accept Pdo~tbt, but also that her doubt steins from tile instantiation of tile amount term as 8800. We hypothesize that U might accept a t)roposition with a different instantiation of tile amount term, lint U doesn't explicitly state this, and other instantiations may be irrelevant. A violated expectation will be referred to as PC and is described further in Section 3.1.2. When and how these expectations arise is a topic for fllture research.</Paragraph>
      <Paragraph position="1"> We assume the t)ropositions Pao~,l,t, Pc, and Pi, as well as the fact that we want to express doubt, as inputs to our generation process. Note that every expression of doubt will be associated with some Pdoubt and solne Pc, since for every expression of doubt, there must be some doubted proposition and some inconsistency between the doubting agent's expectations and belief in Pdoubt. There may or may not be an associated Pi, depending on the doubting agent's beliet~ supporting ~Pdo,,bt. Lack of a Pi indicates that tile agent's belief in ~P(to,tbt is unsupported ~.</Paragraph>
      <Paragraph position="2"> Based on the information that a speaker will ideally convey when expressing doubt (as discussed at the beginning of this section), we hypothesize that the following aspects of a speaker's beliefs are significant factors in how an expression of doubt is realized. null  behind the asserted proi)osition, which imi)acts the strength of tlm hearer's doubt(Chu-Carroll and Car- null berry, 1998) * Expert - The information is coming from a domain expert, or coming from someone with firsthand knowledge (including personal preferences). * Reliable - The agent suggesting the proposition is not an expert, trot is considered a generally knowledgeable source.</Paragraph>
      <Paragraph position="3"> * Questionable - hffbrmation thai; doesn't come fl'om an expert or reliable agent, or that is stated uncertainly by such an agent.</Paragraph>
      <Paragraph position="4">  Pc. feature: /2~ refers to a violated expectation. In the following, we identify three kinds of expectations that may be violated by an assertion. For illustrative purposes, assume that S has made the following assertion: S: The most you will 9et back on your taxes is $~00.</Paragraph>
      <Paragraph position="6"> 5AIthough human agents may generally be able to offer soine weak supt)orl, for their l)ellefs, it is possible, depending on the belief revision system used, to have no supporting evidence for a belief (Logan et al., 1994).</Paragraph>
      <Paragraph position="7"> Tile doubting agent may fail to accept -P, lo,bt with _term instantiated to _value, due to an expectation that _value is not one of tile instantiations of _term that would make -Pdo,,~t true. For example, the hearer of the above assertion by S may have expected a much larger vahm than $400, with little or no support for this expectation.</Paragraph>
      <Paragraph position="9"> The doubting agent may fail to accept -\]~lo~,bt due to an expectation that -Pdo,,~t will be false when _term is instantiated with _value, in situations in which _constraint holds. This constraint is not a term in -Pdo,,~t, lint tile doubting agent believes that the speaker of -l~zo,,~t intends that the constraint hold. For example, the hearer of the above assertion by S may believe that S means $400 for the whole 3,ear, but may have expected a larger amount unless S was referring to, say, quarterly taxes.</Paragraph>
      <Paragraph position="11"> The doubting agent may fail to accept l%~o,,~t in its entirety without having a specific objection to any particular term in tile prol)osition.</Paragraph>
      <Paragraph position="12">  Commonality of Pi refers to tile source of the doubting agent's conflicting belief, if any. * Old - A prior conflicting belief is already i)art of tile explicit common ground of tile dialogue.</Paragraph>
      <Paragraph position="13"> * New - The doubting agent doesn't believe, that her conflicting belief is already part of the common ground estat)lished t)y the preceding dialogue.</Paragraph>
      <Paragraph position="14"> Endorsement of Pi refers to the strength of evidence supporting the belief 1~ that is in eonfiiet with the doubted belief. The endorsements are listed here from strongest to weakest.</Paragraph>
      <Paragraph position="15">  * First-hand - Belief is a personal t)reference or sometlfing directly experienced.</Paragraph>
      <Paragraph position="16"> * Expert - Belief supported 1)y expert testimony, or thought to be common knowledge among experts in tlfis domain.</Paragraph>
      <Paragraph position="17"> * Reliable - Belief conmmnicated from someone who, while not an expert, is generally considered a knowledgeable source of information.</Paragraph>
      <Paragraph position="18"> * Default - Belief believed to be common knowl- null edge, in tim sense that the speaker strongly believes it and strongly believes that others who belong to a certain community (namely one which she has in common with the other dialogue agent) believe it as well.</Paragraph>
      <Paragraph position="19"> awe make the simplifying assumption that only one such proposition has been identified for use in an expression of doubt, as this is 1;he case in all of the expressions of doubt we encountered in our corpus. We leave consideration of expressing multiple l~'s in one utterance for fllture work.  * Derived - Belief is (leriv('.d froln other 1)e.liefs in such a way that it is considered strong.</Paragraph>
      <Paragraph position="20"> * Ilyl)othesis - The 1)elief is derived fl'om other beliefs in such a way that it; is considered weak. This category includes beliefs derived from analogy with another belief in a similar 1)roposition.</Paragraph>
      <Paragraph position="21"> * None - The belief is unsupported.</Paragraph>
      <Paragraph position="22"> Endorsement of hnplication ret&gt;rs to the  strength of evidence SUl)l)Orl;ing the belief that Pi being true ilnl)lies thai; Pdo~,bt is not l;rue. The endorsements are listed from strongest to weakest. Wc assume the salne definitions as the category above and that the two lists lie on the same strength scale. That is, a.n iml)lication endorsed as reliable is the same streng(;h as a P+ endorsed as reliable and stronger tlmn a I} endorsed as hypothesis. The only addition to this list; is the Logical (,Jldorsement to ac(:omd; for instance.s in which P,~,,,,a can I)e logically deduced from Pi.</Paragraph>
      <Paragraph position="23">  * Generic: Sentence that is a general question of the previous utterance.</Paragraph>
      <Paragraph position="24"> h. you .still -you have to file a state income tax return as well j. i do? * Repetition: Rel)etition of a phrase from i)revious utterance.</Paragraph>
      <Paragraph position="25"> h. OK, what I'd likc you to do is lend h, im the 20 thousand.</Paragraph>
      <Paragraph position="26"> 1. 20 thousand? * l/ei)etition+ : l~,et)etitioil of t)hrase froln 1)revious utterance t)lus new intbrmation h. rigM,, the mazimum amount of credit that you will b(', able to get will be $/~00 on their taz rot'am e. $400 for the whole year? * Contradict;: Presentation of a 1)citer t, hat iinl)li(!s the negation of \])do,,bt h. and th, crc's no reason why you shouldn't have an ira for last yr j. well i thought they just started this yr * Contra(licl;+Source: Pre, senta.tion of a (:ontra(lic null l,()ry lmlieJ' and th(' sour(',e of that 1)elief. h had told j he nlust t)ay tax on his $6256 j. ram. h, arry another th, in.q. i have the internal uh revenue uh ask you about that 6256 $ uh since i have the fund he said no! ,so wh, at do i do now? * Explicit+Contradict: ExI)licit statement of disbelief, followed by a contradictory belief. b. well ah, h,c uh, ... h,c belongs to a money markct )t'nd now and uh, th, ey will do that \[invest it in govt securities as part of thcir individual retirement accou'nt\] for him h. i'm not so sure of it.. they may move it ah in(;() a into a govt securities fund, 1)ut i'm not so sure that they can move it into individual securities - check that out</Paragraph>
    </Section>
    <Section position="3" start_page="742" end_page="743" type="sub_section">
      <SectionTitle>
3.3 Realizing an Expression of Doubt
</SectionTitle>
      <Paragraph position="0"> Many of the exi)ressions of doubt in our COlI)tlS are non-ideal, t)ecause they were not recognized as doul)t or because information that was not included in t, he utterance, lint could have been, was ultimately needed to resolve the doul)t. Thus it was not al)l)ropriate to use the corlms as training data tbr machine learning. Consequently, tile following rules are l)ased  and implication beliefs that would have caused tile form of expression of doubt to be generated. We also encouraged subjects to write in beliet's which were not inchlded, but none (lid. Out of the 60 instances (ten expressions of doubt times six subjects), tim subjects five times chose beliefs that we did not represent as contributing to the doubt and three times failed to recognize a belief that (lid contribute.</Paragraph>
      <Paragraph position="1"> The subjects also rated the beliefs according to strength. We evaluated these ratings to see if the communicated strengths were correlated with the endorsements of beliefs that would have generated this form. Since subjects varied in the ranges that I;hey used in rating the strengths of the beliefs, we looked at tile scores relative to each subjects ratings of the other beliefs.</Paragraph>
      <Paragraph position="2"> Most of the strength ratings were consistent with the rules. The most fi'equent inconsistency was the case in which we would have generated a form based on slightly different endorsements for Pi and the in&gt; plication, but our subjects rated them equivalent strengths. While it may be the case that tmotfle don't actually perceive a difli;renee, it may also be the case that numerical ratings don't fully capture the same information that t, he notion of endorsements do.</Paragraph>
      <Paragraph position="3"> The only significant inconsistency with our rules was one utterance ill which doubt was expressed by &amp;quot;1 thought that, but my husl)and, lie wasn't sure if that just uleant ss pension.&amp;quot; We had represented the, husband as a relial/le source an(l t;hus generated illformatioll about the, source of the conflicting propo sit;ion. In this instance, the doul)t was not judged very strong l)y our subje(:ts, and tlm agent's t)eli(~f in her husband's exl)ertise as relatively weak. In future work, we will further explore exi)ression:s of doubt for which it is imi)ortant to (:omnmnicate the som'(:e of inforlnation.</Paragraph>
      <Paragraph position="4"> \Ve consider this a l)reliminary (;valuation to show that the rules we have l'ormulated thus fitr are re;&gt; sortable, l?urther evahlation will tie neexle, d to provide cvitlem:e that subjects really do draw &amp;J.\[('rcnt inferences based on the different forms of exl)ression and that our rules accurately captnr(. ~ these ditti?reUCeS. null</Paragraph>
    </Section>
  </Section>
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