Common Ground and the Understanding of Demonstrative Reference

JOURNAL OF VERBAL LEARNING AND VERBAL BEHAVIOR 22, 245--258 (1983)Common Ground and the Understanding of Demonstrative ReferenceHERBERT H. CLARKStanford Universi~ROBERT SCHREUDERUniversi~ ~Lei~nSAMUEL BUTTRICKStanford UniversitySuppose a speaker gestures toward four flowers and asks a listener, "How would you describethe color of this flower?" How does the listener infer which of the four flowers is being referredto? It is proposed that he selects the one he judges to be most salient with respect to the speaker'sand his common ground--their mutual knowledge, beliefs, and suppositions. In a field experiment,it was found that listeners would accept demonstrative references (like this flower) withmore than one potential referent. Three further experiments showed that listeners select referentsbased on estimates of their mutual beliefs about perceptual salience, the speaker's goals, andthe speaker's presuppositions and assertions. Common ground, it is argued, is necessary ingeneral for understanding demonstrative reference.A demonstrative reference is a reference thatrequires an accompanying gesture for its completeinterpretation. Suppose Margaret pointsat a copy of the New York Times that Duncanis holding and asks Duncan(1) Could I look at that newspaper?To understand what she is referring to, Duncanmust not only grasp the words that newspaper,but also register what Margaret is indicatingby her gesture, or demonstration,which could have been a nod, a gaze, a presentation,or some other gesture.Demonstrative references at first seem trivialto understand. In (1), let us call newspaper,the descriptive part of the noun phrase,the descriptor, and the newspaper Margaret isThe research reported here was supported in part byGrant MH-20021 from the National Institute of MentalHealth and by the Nederlandse Organisatie voor Zuiver-Wetenschappelijk Onderzoek. For helpful suggestions onthe research and manuscript, we thank Eve V. Clark,Richard J. Gerrig, Ray W. Gibbs, Jr., Barbara C. Malt,Gregory L. Murphy, and Deanna L. Wilkes-Gibbs. Requestsfor reprints should be sent to Herbert H. Clark,Department of Psychology, Jordan Hall, Stanford University,Stanford, Calif. 94305.245pointing at the demonstratum. Standard theoriesof demonstrative reference (e.g., Bennett,1978; Fillmore, 1982; Lakoff, 1974;Lyons, 1975, 1977; Maclaran, 1980) make twotacit assumptions about such a reference. Assumption1: The referent is identical to thedemonstratum. If Margaret is referring to anewspaper, she must be pointing at that newspaper.Assumption 2: The referent is uniquelydetermined by the demonstratum together withthe descriptor. With her gesture, Margaretspecifies a set of potential referents--thenewspaper itself, the newsprint, a headline,and many other possibilities--and with thedescriptor newspaper, she uniquely specifieswhich element in that set, the newspaper itself,is the intended referent. With Assumptions1 and 2, it seems obvious how peopleunderstand demonstrative references.The problem is that both assumptions areincorrect. Suppose Margaret points at the samenewspaper and asserts(2) I used to work for those people.Although she is demonstrating a newspaper,she is referring to its publishers, the New York0022-5371/83 $3.00Copyright © 1983 by Academic Press, Inc.All rights of reproduction in any form reserved.

DEMONSTRATIVE REFERENCE 247nically the mutual knowledge, beliefs, and assumptionsshared by the speaker and addressees(see Clark & Carlson, 1981; Clark & Marshall,1981). In our proposal, the speaker intendseach addressee to base his inferencesnot on just any knowledge or beliefs he mayhave, but only on their mutual knowledge orbeliefs--their common ground. One goal ofour research is to explore the role commonground plays in demonstrative reference.Underdetermined Demonstrative ReferenceLet us turn now to underdetermined demonstrativereference. Suppose Julia nods ata cluster of men jogging along a road and tellsKen(4) That man is my neighbor.If Ken takes d to be the set of ten men, andr to be one of them, what F should he infer?If one jogger was naked, he might infer F tobe naked-man-in. If exactly one jogger wasespecially tall, a midget, or in a gorilla suit,or if one had just fallen, won the race, orslugged a bystander, he would infer a differentF and r. In each case, he would choose Fto make r the most distinctive man in the cluster.The F would have the general form mostsalient-part-of.This characterization, however, cannot becomplete. Each jogger is the most salient bysome criterion--by being the only one withred hair, in second place, or wearing bluesocks. In what respect is the intended referentmost salient? Suppose Julia had just told Kenthat her neighbor was completely bald, andsuppose all the joggers except one were hirsute.In saying (4), Julia would expect Ken tosee that this prior information, part of theircommon ground, was relevant. He was to pickthe jogger most salient not on general grounds,but against their particular common ground.He was to select the bald man even if thetallest man, the midget, or the winner wouldbe most salient on general grounds. As theprinciple of optimal design dictates, the onlyinformation he should consult is their commonground. So the general form of F shouldbe most-salient-part-of-with-respect-to-common-ground.The common ground between two people isbased on roughly three sources of information(Clark & Marshall, 1981). The first is perceptualevidence, what the two have jointlyexperienced or are jointly experiencing at themoment. The second is linguistic evidence,what the two have jointly heard said or arenow jointly hearing as participants in the sameconversation. The third is community membership.They take as common ground everythingthey believe is universally, or almostuniversally, known, believed, or supposed inthe many communities and subcommunities towhich they mutually believe they both belong.Most parts of common ground are basedon a combination of these sources.Two people's common ground may be a tinyplot or a large acreage. If Julia and Ken arestrangers, their common ground comes entirelyfrom their joint membership in the communityof, say, adult Americans (mutuallyrecognized from their American accents) andfrom the scene they are witnessing. If Juliaassumed nakedness would be the most salientattribute in the scene for most Americans, shewould expect Ken to understand her in (4) asreferring to the naked jogger. But if Julia andKen are intimates, their common ground willbe extensive and include their discussion ofher bald neighbor, and Ken should understandher as referring to the jogger who is bald. Forthe same demonstratum and descriptor, the relationF, and hence the referent r, shouldchange with common ground.At first, one might view the underdetermineddemonstrative references in (2) through(4) simply as defective, as no different fromthe equivalent underdetermined definite descriptions.If they were, they should be replaceableby underdetermined definite descriptionswith no change in understandability.They are not. Suppose Margaret uttered (1')through (4') in the same contexts as (1) through(4), but without the accompanying gestures.(1 ') Could I see the newspaper in your hand?(2') *I used to work for the people in yourhand.(3') *Could I see the newspaper in yourhand?

248 CLARK, SCHREUDER, AND BUTTRICK(4') *The man in the group in front of usis my neighbor.While most people we have asked find (1')acceptable, they find (2') through (4') unpalatable.They feel as if they are left with thequestions "What people? .... Which newspaper?"and "Which man?" whereas they accept(2) through (4) without such questions.When a reference is accompanied by a demonstration,listeners seem to feel they are tounderstand it partly by examining the demonstratummore closely. Demonstrative referencesare simply different from other definitedescriptions (Hawkins, 1978).Before examining this common groundmodel further, we need to demonstrate thatAssumption 2 is false--that people will acceptdemonstrative references with more thanone potential referent. That was the aim ofExperiment 1.EXPERIMENT 1We stopped students on the Stanford Universitycampus, showed them a photographwith four types of flowers in it, and asked,gesturing to the photograph as a whole, "Howwould you describe the color of this flower?"We expected them to respond in one of threemain ways:(a) Implicit acknowledgement of understanding,"It's yellow."(b) Request for confirmation, "Do youmean this flower [pointing at one of theflowers]?"(c) Request for clarification, "Which flowerdo you mean?"Response (a) indicates the students thoughtthey understood the reference; (b) indicatesless certainty; (c) indicates the least certainty,since the students do not even offer the conjecturethey do in (b). Put negatively, (b) indicatesthey thought the reference was partlydefective, and (c), rather more defective. With(a), (b), and (c), we have a natural scale ofunderstandability.MethodThe color photograph we used, from theSunset New Western Garden book (1979, p.128), depicted four varieties of flowers besidea wooden fence: a cluster of yellow daffodilsin the front center; white daisies dispersedthroughout the background; a number of orangeCalifornia poppies at the right; and acluster of blue irises on the far left. We comparedtwo versions of the photograph. Picture1 was a color Xerox copy of the photograph,measuring 18 by 24 cm, in which the daffodilswere only slightly more prominent than theother three flowers. Picture 2 was a secondcolor Xerox copy, cropped to 11 by 15 cm,in which the daffodils were clearly more salientthan the others. The two pictures eachshowed all four types of flowers but differedin the prominence of the daffodils.One of us, Buttrick, approached 40 studentsat various places on the Stanford Universitycampus. With a clipboard in hand, heintroduced himself to each student, handed thestudent one of the two pictures, and, noddingat the picture while preparing to write downthe answer, asked, "How would you describethe color of~this flower?" He wrote downeverything the student said, including all requestsfor confirmation or clarification. Theflower chosen was always clear from the colornamed or flower pointed at. Each picture wasdescribed by 20 students.Results and DiscussionSuppose that listeners look where the speakeris pointing, note the set of potential referentsthere (the referent array), and select the objectuniquely specified by the descriptor. Thismodel, which is much like Olson's (1970)model of definite reference, is based on Assumptions1 and 2. We will call it the classicalmodel. According to that model, if thereferent array contains four flowers, listenersshould accept a descriptor like daffodil, whichpicks out a unique flower, but they should notaccept flower, which does not. Yet as shownin Table 1, many students in Experiment 1accepted flower without hesitation. For Picture2, 11 of 20 students immediately describedthe color of the daffodils. For the twopictures together, 14 of 40 students did so. Toanticipate a finding in Experiment 4, 12 of 15students gave response (a) for a similar pic-

250 CLARK, SCHREUDER, AND BUTTRICKcommon ground with the anonymous student.If she takes this as a "unique signal" for coordinatingtheir expectations, she will pick thebasketball. Let us call such a choice on aSchelling task a Schelling choice.But suppose Mary is told her partner is Peter,with whom she regularly plays squash.Because she could assume the squash ball wasparticularly salient in their common ground,she could select it, believing Peter too wouldsee it as a "unique signal" for coordinatingexpectations. No matter how avid a squashplayer she was, she could not make the sameassumption when her partner was just "anotherstudent." It matters to Mary who herpartner is because it matters what is in theircommon ground.Schelling choices, therefore, should reflectwhat the two partners take to be salient withrespect to their common ground. In the commonground model, listeners choose referentsby the same criterion--salience with respectto common ground--and so the distributionof Schelling choices should predict theirchoices of referents. It should also predict theirconfidence. In a Schelling task, if object A isselected more often than object B, then in thecorresponding reference task those listenerswho happen to select A should be more confidentthan those who happen to select B. Experiments2 and 3 were designed to test thesepredictions.EXPERIMENT 2Students were asked to interpret demonstrativereferences from a speaker they did notknow. In assessing common ground, therefore,they could make only the most generalassumptions about the display and how it wouldbe viewed by most people. In fact, peoplegenerally have a pretty good idea of what otherswill attend to in such a display, especiallywhat they will see as salient, distinctive, orout of place. These estimates should be thesame ones they use in making Schelling choicesand, more simply, in choosing the most salientobject.MethodWe constructed 27 displays of common objectsby cutting pictures out of merchandisecatalogs from such department stores as Sears,J. C. Penney, and Best Products. Each displaydepicted two to seven objects of the sametype, like four watches, six lamps, or threetents, each with a number or letter next to itfor identification. The displays was designedso that one object in each display seemed moreprominent than the rest--larger, more distinctivein shape, more foregrounded--and so thatthe prominence of the most prominent objectvaried from display to display. The 27 displayswere placed in one order and photocopiedto make three booklets that differed onlyin the sentence typed at the bottom of eachpage: "What do you think of this X" for areference task, "You are both to choose thesame X" for a Schelling task, and "You areto choose the most prominent or salient X"for a salience task. For X we substituted aone- or two-word description of the objects inthe picture--for example, watch, lamp, or tent.Reference task. Ten students were instructed,"Imagine that you and another personare looking through this catalog. He showsyou this page and asks you the question printedat the bottom (for example, 'What do you thinkof this alarm clock?'). You are to indicatefor each display which object you thinkhe is referring to. After you have made yourchoice, please indicate how confident you arethat you have chosen the correct referent."They rated their confidence on a 7-point scale,with 1 meaning "no confidence" and 7 "veryconfident."After the students had finished, they wereasked to go through the displays again andrank the remaining objects for how likely eachone was to be the intended referent. They werethen asked to describe for each display thecriteria on which they had based their initialchoices. Since the reference choices and confidenceratings were collected first, they couldnot be influenced by the later judgments.Schelling task. Ten other students were instructed,"Imagine that you and another personwhom you do not know are looking atthese displays. If you can both independentlyselect the same object, you will win a prize.If you fail to choose the same object then youlose." Otherwise, they followed the same

DEMONSTRATIVE REFERENCE 251procedure as in the reference task. They wentthrough the 27 displays one time makingchoices and confidence ratings, a second timeranking the remaining objects, and a third timedescribing the criteria for their choices.Salience task. Ten more students were askedto choose for each display "the most prominentor salient X." They too went through thedisplays three times, once making choices andsalience ratings, a second time giving ranks,and a third time describing their criteria.The 30 students were Stanford Universityundergraduates participating either as a courserequirement or for pay. They worked in groupsof two to four in sessions lasting about 45minutes. The first three displays were consideredpractice and later discarded.ResultsThe choices in the reference task generallycoincided with those in the Schelling and saliencetasks• In each display for each task, oneobject tended to be chosen more than any other.Let us call this the major choice. In the referencetask, the percentage of students makingthe major choice averaged 70% (rangingfrom 40 to 100%). The percentages in theSchelling and salience tasks averaged 81 and89%, respectively• So within tasks, the studentsshowed considerable agreement. Themajor choices also tended to coincide acrosstasks. For 18 of the 24 displays, they wereidentical for the three tasks; for all 24 displays,they were identical for at least two ofthe three tasks• For each display we can identifythe one object on which the largest numberof students agreed across all three tasks.The percentage of students making that choiceaveraged 67%, which is near the maximumpossible of 70%, the average percentage ofstudents making the major choice on the ref-erence task. So the major choices in the threetasks are in good agreement.A second way to show agreement across thethree tasks is to compare the rankings of theobjects in each display. For each task, wecomputed the mean ranks for the two to sevenobjects in each display; we then correlated themean ranks, for each display separately, betweenthe reference and Schelling tasks, betweenthe reference and salience tasks, andbetween the Schelling and salience tasks• These72 correlations (3 comparisons for 24 displays)had a mean of .81 and a median of .85.Table 2 shows the means, medians, and rangesof these correlations for the three comparisonsseparately. The mean correlations for the threecomparisons were very similar, ranging from• 80 to. 84, as were the medians, which rangedfrom .83 to .89. So this measure, too, is inline with the common ground model: thechoices in the reference, Schetling, and saliencetasks were very similar.The students in Experiment 2, as in Experiment1, ranged widely on most displays inhow confident they were in their initial choices,from 1 ("no confidence") to 7 ("very confident").These ratings yielded a surprisingfinding: the more popular a given choice turnedout to be--without anyone knowing this, ofcourse--the more confident were the peoplewho had made it.There are several ways of demonstrating this.Consider the reference task. For each display,we can compare the mean confidence on themajor choice with the mean confidence on theother choices. For the 17 displays where wecould compute both means, the majority choiceaveraged 4.6 (on the 7-point scale) andthe other choices averaged only 3.6, minF'(1,19) = 5.19, p < .05 (see Clark, 1973)•The corresponding two means for the Schell-TABLE 2MEANS, MEDIANS, AND RANGES OF THE 24 CORRELATIONS COMPUTED ON THE MEAN RANKS OF THE STUDENTS' CHOICESBETWEEN THE REFERENCE, SCHELLING, AND SALIENCE TASKS (EXPERIMENT 2)Pairs of tasks Mean Median RangeReference and Schelling tasks .80 .89 0.33-1.00Reference and salience tasks .80 .83 0.27-1.00Schelling and salience tasks .84 .89 0.21-1.00

252 CLARK, SCHREUDER, AND BUTTRICKing task were 5.0 and 3.9, min F'(1,23) =15.20, p < .01, and for the salience task, 6.1and 5.2, min F'(1,15) = 7.37, p < .025.The same point can be illustrated in anotherway. For each task, we classified each student'schoice on each array by how many ofthe ten students concurred on that choice, andthen computed the mean confidence rating ofeach of these ten categories (1 to 10 studentsconcurring on the choice). In the referencetask, for example, there were four separatedisplays in which eight students agreed on asingle object within the display. These 32confidence ratings averaged 5.2. The ten meanratings computed this way for each task areplotted in Figure 1.In all three tasks, the more students whoconcurred on a choice, the more confident werethe students who made that choice. In the reference,Schelling, and salience tasks, the meancorrelations were .79, .91, and .92, respectively.These three coefficients are each significantlygreater than zero, F(1,9) > 14.94,p < .01, and they are not significantly differentfrom one another. Figure 1 also shows,for the major Schelling choices only, the meanconfidence ratings from the reference taskas predicted from the number of studentsconcurring on their Schelling choices. Thecorrelation here, despite a restricted range,was .75.Although the three tasks should be verysimilar to each other, the salience task shouldstand out in one respect. In the reference andSchelling tasks, the students rated their confidencein whether their choice would be thesame as the choice of another person, someonethey did not know. But in the saliencetask, they rated the salience as they alonejudged it, without any implied comparison withanother person's judgments. So the studentsin the reference and Schelling tasks should beless confident that they knew what other peoplewould do than the students in the saliencetask should be in what they themselves thought.Indeed, for the reference and Schelling tasks,REFERENCESCHELLING6-5-o o o 04-4-3-LLIoZ 2-ILla,-r 1Z oO-t,.) 7.Z,~ 6.LLI5.oSALIENCEr~.793-2.l-,o7-SCH./REE6.r=.914-2- 2-r=.92PEOPLE CONCURRING ON CHOICEFIG. 1. The mean confidence ratings for choices plotted against number of students concurring on eachchoice, for the reference, Schelling, and salience tasks separately, and for the reference choices plottedagainst number of students concurring on the major choices in the Schelling task (Experiment 2).fr=.75

DEMONSTRATIVE REFERENCE 253the mean confidence ratings were 4.4 and 4.8,but for the salience task it was 5.8, whichis significantly larger than the other two,F(1,27) > 5.76, p < .05.The criteria the students gave for theirchoices were virtually identical across the threetasks. As representative of all three, here is abreakdown of the 240 reasons for the referencetask: 52% mentioned visual features suchas size, shape, color, or special markings; 17%mentioned functional properties such as havinga carrying case or being simplest to operate;12% mentioned position in the display,such as being in front; 12% were vague, as in"most unusual," "unique," "different fromothers," or the like; 4% expressed personalpreferences such as "the one I'd be most likelyto buy"; and 4% were claims of "don't know"or "no special reason." So about 80% of thereasons mentioned perceptually salient featuresexplicitly; many of the rest could beclaims about salience in common ground withpeople in general. Only one, "My roommatehas that kind of basketball," was impossibleas a statement about common ground with thespeaker.DiscussionAlthough the classical model does not sayanything about the relations among reference,Schelling, and salience choices, the commonground model does. Students in the referencetask should select in each display that objectthey think is most salient in their commonground with the speaker. So they should reasonin the critical respects just as they wouldin making a Schelling choice, and they did.The reference choices were well accounted forby the Schelling choices. But the only commonground the students could appeal to ineither task was their estimate of how peoplein general would see the displays--what theywould judge to be perceptually salient orprominent. So the reference and Schellingchoices should also agree with the saliencechoices, and they did.People's confidence in their choice of referentsranged widely on the very same display.What is remarkable is how accurate theywere in estimating their confidence. When Johnand Mary--pseudonyms for two students--were faced with three clocks in display 9, Johnchose clock A with a confidence of 6, andMary chose clock B with a confidence of 3.They presumably made the best choices theycould, but just came to different conclusions.Still, each one judged the validity of his orher own choice accurately. John's confidencein clock A was justified, since 80% of thestudents concurred on this choice. Mary's lackof confidence in clock B was also justified,since no other person agreed with her. So peopleare quite deft in estimating not merelywhich object is most likely the intended referent,but also how likely it is to be the intendedreferent. They need both estimates ifthey are to know when they should ask forconfirmation or clarification.All the findings so far could be accountedfor by a perceptual model in which the addresseewould compare the perceptual salienceof all objects in a display and then choosethe most salient one. He would not considerthe speaker's point of view at all, let alonethe common ground they shared. Experiment3 was designed to test this model.EXPERIMENT 3For most demonstrative references, thecommon ground contains more than the scenepointed at and assumptions about how it isgenerally viewed. It also contains what hasjust been discussed and implied in conversationand, among acquaintances, other informationtoo. In the perceptual model, addresseesshould ignore all other information andselect the perceptually most salient object regardless.In the common ground model, theyshould select the object most salient againstall the information in common ground.In Experiment 3, it was made commonground that the speaker was buying a presenteither for his old conservative Uncle Georgeor for his young modern Cousin Amanda. Inthe common ground model, that should makea difference. To a question like "What do youthink of this watch?" addressees should selectone watch with Uncle George in mind andperhaps quite a different watch for Cousin

254 CLARK, SCHREUDER, AND BUTTRICKAmanda. Perceptual salience should be relevant,but only as weighed against the rest ofcommon ground. By contrast, in the perceptualmodel the speaker's purpose should makeno difference. Addressees should select thesame watch regardless of who the speaker wasshopping for.MethodWe constructed 21 displays like those inExperiment 2, but each with four objects. Eachdisplay was designed so that two objects (say,watches) seemed more appropriate for CousinAmanda and the other two more appropriatefor Uncle George. Again the first three displayswere considered practice.Reference task. We prepared several bookletsby photocopying the 21 displays with"What do you think of this X?" at the bottomof each display, where X was the appropriateone- or two-word description. Ten studentswere instructed, "Imagine that your neighboris looking for a present for his Uncle George.He shows you this catalog and asks 'What doyou think of this X?' You are to indicate foreach display what object you think yourneighbor is referring to." There were ten otherstudents for Cousin Amanda. Uncle Georgewas described as a middle-aged, conservative,thrifty bachelor and Cousin Amanda asa rich, young, modern jet-setter.As in Experiment 2, the students wentthrough the booklets three times, once makingreference choices and confidence ratings, asecond time ordering the" other objects in eachdisplay, and a third time describing criteriafor their choices.Schelling task. In this set of booklets, thesentence read "You are both to choose thesame X." Ten students were instructed,"Imagine that your Uncle George has lookedthrough this catalog and has chosen one objectfrom each display. Your task is to pick thesame object as your Uncle George. If and onlyif you have both chosen the same object willyou win a prize. If you fail to agree in yourchoice, then you lose." There were 10 otherstudents for Cousin Amanda. Uncle Georgeand Cousin Amanda were described as in thereference task. All 20 students followed thesame procedure as in Experiment 2, givingchoices, confidence ratings, rank orders, andrating criteria.The 40 students, from the same source asin Experiment 2, worked in groups of two tofour in sessions lasting about 45 minutes.Results and DiscussionThe reference and Schelling choices forUncle George were like each other, but unlikethose for Cousin Amanda. To show this, wecomputed the mean ranks of the four objectsin each display in each task, and then correlatedfor each display separately the mean ranksfrom the four tasks. The means of these correlationsare listed in Table 3. If the studentsmade the same choices in the reference andSchelling tasks for the same person, the correlationsbetween these two tasks should behighly positive, and indeed they were. These18 correlations averaged .75 for Uncle George,and .72 for Cousin Amanda, F(1,17) = 87and 53, respectively, p < .001. If the studentsmade roughly complementary choicesfor Uncle George and Cousin Amanda, thefour cross-correlations among the UncleGeorge and Cousin Amanda tasks should benegative, and they were. The means rangedfrom -.25 to -.44, all F(1,17) > 5.17,p < .05, except for -.25, F(1,17) = 2.45.If the perceptual model were correct, thestudents should have selected the same perceptuallysalient object from each display regardlessof who the present was for, but theydid not. By the common ground model, theyshould have considered the common groundinformation about who the present was for,and they did. Their choices in the referencetask were predicted by the Schelting choices,but only when the recipient of the gift was thesame in the two tasks. So for both choices,the students considered perceptual salience onlypart of the pertinent information in commonground.The reasons students gave for their choiceswere nearly identical for the reference andSchelling tasks, but differed markedly betweenUncle George and Cousin Amanda. Inthe reference task, about 75% of the 360 reasonsmentioned visual or functional features,

DEMONSTRATIVE REFERENCE 255TABLE 3MEANS OF THE 18 CORRELATIONS COMPUTED ON THE MEAN RANKS OF THE'STUDENTS' CHOICES BETWEEN THE REFERENCEAND SCHELLING TASKS WITH UNCLE GEORGE AND COUSIN AMANDA AS RECIPIENTS OF GIFTS(EXPERIMENT 3)Task 2 3 41. Reference task for Amanda + .72 - .35 -.252. Schelling task for Amanda - .44 - .373. Reference task for George + .754. Schelling task for Georgeas in Experiment 2. But unlike the previousexperiment, most of these features fit the stereotypefor Uncle George or Cousin Amanda,as with "modem design" and "it looks sleek"for Cousin Amanda, and "simplest to use"or "reliable" for Uncle George. Indeed, it isdifficult to distinguish these reasons from another19% that simply identified one object astailored to one of the two stereotypes, as with"conservative," "plainest," or "fashionable."Another 2% mentioned personal preference,and 4% were vague or "don't know."Only one reason could possibly be typed asegocentric--"It's the only kind I've everseen." So over 90% of the reasons mentionedfeatures presumed to be in common ground,and most were tailored to the stereotype ofwho the gift was for.ASSERTIONS AND PRESUPPOSITIONSOne of the surest ways to introduce informationinto common ground is to mention itin conversation. In Experiment 3, the speaker'sgoal could have been mentioned in a priorutterance, as in "I am looking for a presentfor Uncle George-What do you think of thisstopwatch?" or in the question itself, as in"What do you think of this stopwatch as apresent for Uncle George?" and it probablywould have made little difference. But thereare many ways of mentioning a piece of information--byasserting or presupposing it,in a prior utterance, the same utterance, or afuture utterance, and explicitly or by implication.A listener must often take account of whatis being asserted about the referent. Supposetwo men are walking down the street, one veryfat and the other very thin, and you say (5),(6), or (7) to a companion as you nod in theirdirection.(5) That man weighs too much for his owngood.(6) That man weighs too little for his owngood.(7) That man is my neighbor.In (5) and (6), the only way your companioncan find a demonstrative relation F is by usingwhat you are asserting about the referent; youwould assert (5) of the fat man and (6) of thethin man, but not vice versa (unless you werebeing ironic). In (7), where he can find noreasonable relation, he is uncertain.The interpretation of the assertion must itselfbe common ground. Suppose you pointat the same two men but say instead(8) That is what George will look like verysoon.If you had been talking about George gainingweight, your companion would take you asreferring to the fat man as in (5). If you hadbeen talking about George losing weight, hewould select the thin man as in (6). Withoutsuch information, he would be uncertain. In(8), then, your companion appeals to the commonground specifically established betweenhim and you. An overhearer not privy to yourearlier conversation would be uncertain regardlessof what your companion thought (seeClark & Carlson, 1982).The common ground needed may includequite specialized information as well. Supposefor the same two men you utter (9), (10),or (11).(9) That man is a real Falstaff.(10) That man is a real Don Quixote.(11) That man is a real George Smith.Your companion must appeal to the knowl-

256 CLARK, SCHREUDER, AND BUTTRICKedge he assumes the two of you share, as educatedadults, of Falstaff and Don Quixote for(9) and (10), and as friends of thin GeorgeSmith for (11). An educated but unacquaintedoverhearer might guess (9) and (10), but couldnot interpret (11).These arguments have been based on intuitionsabout demonstrative references in context.Experiment 4 was a field experiment designedto substantiate even subtler intuitionsabout the use of presuppositions.MethodEXPERIMENT 4For this experiment, we used a picture fromNewsweek Magazine of President Ronald Reagansitting with David Stockman, then thedirector of the Office of Management andBudget. We supposed that virtually everyoneat that time would assume Reagan was veryfamiliar to most people and Stockman less familiar.As interviewer, Buttrick approached30 students one at a time on the Stanford Universitycampus, showed them the picture, and,while recording their responses on a clipboard,asked half of them Question 1 and theother half Question 2.Question 1. You know who this man is,don't you?Question 2. Do you have any idea at allwho this man is?With Question 1, Buttrick appeared to presupposethe student would surely know who"this man" is. With Question 2, he appearedto presuppose the opposite. If people rely onsuch presuppositions, the students should tendto select Reagan for Question 1 and Stockmanfor Question 2. To check our assumptions aboutReagan's and Stockman's familiarity, Buttrickthen asked each student to rate how recognizableReagan and Stockman would eachbe to the general public on a 1 to 7 scale with1 being "very low" and 7 being "very high."He also asked them to identify either man theyhad not yet named.Results and DiscussionQuestions 1 and 2 led to different choicesof referents. The 30 responses are summarizedin Table 4. For Question 1, 14 of 15students chose Reagan, 12 outright and 2 tentatively;none chose Stockman. For Question2, 7 of 15 students chose Stockman, 3 outrightand 4 tentatively; only 2 chose Reaganand they did so tentatively. This difference ishighly significant, X~(1) = 15.65, p < .001.As expected, Reagan was judged more recognizablethan Stockman, 6.2 to 2.3,t(29) = 30, p < .01. All 30 students identifiedboth Reagan and Stockman correctly.The perceptual model cannot account forthese findings. If it were correct, there shouldbe no difference between Questions 1 and 2,since the referent should be chosen entirelyon the basis of perceptual salience. But therewas a difference. By the common groundmodel, the students should use Buttrick's apparentpresuppositions in their rationales forselecting Reagan versus Stockman. When heappeared to presuppose they knew the referent,they should select Reagan, reasoning thatReagan is better known than Stockman; whenhe appeared to presuppose the opposite, theyshould select Stockman. And that is what occurred.TABLE 4RESPONSES TO QUESTION 1 ("You KNOW WHO THIS MAN IS, DON'T YOU. 9'') AND QUESTION 2 ("Do YOU HAVE ANY IDEAAT ALL WHO THIS MAN IS?") IN EXPERIMENT 4Response Question 1 Question 21. Selects Reagan 12 02. Points at Reagan, "This one?" 2 23. Selects Stockman 0 34. Points at Stockman, "This one?" 0 45. "Which one?" 1 56. Identifies Reagan and Stockman 0 1Totals 15 15

DEMONSTRATIVE REFERENCE 257The students were more certain in answeringQuestion 1 than Question 2. Let us call aresponse uncertain if it was a request for confirmationor clarification. Only 3 of 15 studentswere uncertain for Question 1, as comparedwith 11 of 14 students for Question 2,X2(1) = 7.74, p < .01. There are severalpossible reasons why. The students might havebeen more certain of their answer to Question1 than to Question 2. Or they might have beenmore ready to assume Buttrick was referringto the more recognizable man, namely Reagan.Or Reagan might have been slightly moreprominent perceptually. Whatever the reason,it does not affect the conclusion that the studentsrelied heavily on the speaker's apparentpresuppositions.GENERAL DISCUSSIONDemonstrative references are not simple. Tounderstand the reference in "How would youdescribe the color of this flower?" the studentsin Experiment 1 had to appeal to the"relevant context" and draw certain inferences.The "relevant context," we have argued,consists of the common ground betweenthe speaker and addressees, and the inferencesneeded are based on the principle of optimaldesign, which governs language use in general(see Clark, 1983b). The students had tofind a demonstrative relation F to get themfrom the demonstratum d (the picture of fourflowers) to the referent r (one of the fourflowers). The F could not be just any relation.It had to be the one they believed they wereintended to infer on the basis of commonground.To infer F for underdetermined demonstrations,we have argued, people try to select theobject that both fits the descriptor and is themost salient against common ground. They dothis in much the same way they find the bestsolution in a Schelling task. They assume thespeaker and addressees "must 'mutually recognize'some unique signal that coordinatestheir expectations of each other" (as Schellingput it), and they take that signal to be themost salient object in their common ground.In Experiments 2 and 3, choices in the ref-erence task were well accounted for by thecorresponding Schelling choices.People must weigh every part of commonground that might be pertinent. We have demonstratedthe influence of four such parts:1. Perceptual salience. Each demonstraturnin our experiments consisted of an arrangementof objects, and students could estimatehow people in general would view thesearrangements. When there was no other pertinentinformation in common ground, theywould simply select from the display the perceptuallymost salient object, which is the onlyobject they could be expected to pick outuniquely. In Experiment 2, as predicted, thereference choices were well accounted for bythe salience judgments.2. Speaker's goals. When the speaker'sgoals are part of common ground, they areoften crucial to the interpretation of an utterance(see Clark, 1978, 1979; Cohen & Perfault,1979; Gibbs, 1981). The utterance "CityHall, please" would be interpreted one wayby a taxi driver, but another way by a telephoneoperator because of what they presumeto be common ground about the speaker'sgoals. The speaker's presumed goals are justas important for demonstrative reference. InExperiment 3, when it was common groundthat the speaker was looking for a present forUncle George, the listener's choice of referentwas based on this goal in combination withperceptual salience.3. Speaker's assertions. What the speakerasserts also becomes part of common ground,and it too can influence the listener's choiceof referent. To interpret "That man weighstoo much for his own good," the addresseehad to use what was asserted about the referent.An overhearer unable to understand theassertion, as in "That is what George willlook like soon," might be unable to pick outthe right referent.4. Speaker's presuppositions. What thespeaker presupposes in his utterance is alsopart of common ground and potentially relevant.This was demonstrated in Experiment 4for two kinds of presuppositions. When Buttricksaid "You know who this man is, don't

258 CLARK, SCHREUDER, AND BUTTRICKyou?" he appeared to presuppose explicitlythat "this man" was a man the student wouldsurely know. He also appeared to presuppose,implicitly, that it was common ground thatReagan was better known than Stockman. Sofor this question, the students readily choseReagan, but for "Do you have any idea at allwho this man is?" they tended to chooseStockman instead.When people are addressed by someone,they ordinarily assume the speaker has donehis best to enable them to understand him. Itis on this assumption, the principle of optimaldesign, that they can reason through to thereferent. Yet people also recognize that thespeaker can make misjudgments--especiallyabout common ground. When they detect misjudgments,they have several options. Theycan guess, with the possibility of revising theirguess later; they can guess but ask for confirmation;or they can directly ask for clarification.In Experiments 1 and 4, students wereindeed more likely to ask for confirmation orclarification the less well designed the referencewas.Demonstrative reference is perhaps the prototypeof expressions that cannot be understoodwithout appeal to context. But whatcontext? If our proposal is correct, all the informationthe listener should ever appeal to isthe speaker's and addressees' common ground.Similar claims have been made for the use andunderstanding of conventional and novelwords, assertions, presuppositions, direct andindirect speech acts, and definite reference (seeClark, 1983a; Clark & Carlson, 1981; Clark& Marshall, 1981; for reviews). If these claimsare correct, it will be crucial to study howpeople create, represent, and access commonground.REFERENCESBENNETT, M. Demonstratives and indexicals in Montaguegrammar. Synthese, 1978, 39, 1-80.CLARK, H. H. The language-as-fixed-effect fallacy: Acritique of language statistics in psychological research.Journal of Verbal Learning and Verbal Behavior,1973, 12, 335-359.CLARK, H. H. Inferring what is meant. In W. J. M. Levelt& G. B. Flores d'Arcais (Eds.), Studies in the perceptionof language. London: Wiley, 1978.CLARK, H. H. Responding to indirect speech acts. CognitivePsychology, 1979, 11, 430-477.CLARK, H. H. Making sense of nonce sense. In G. B.Flores d'Arcais and R. Jarvella (Eds.), The processof language understanding. New York: Wiley, 1983a.CLARK, H. H. Language use and language users. In G.Lindzey and E. Aronson (Eds.), Handbook of socialpsychology. Reading, Mass.: Addison-Wesley,1983b, Third edition.CLARK, n. n., • CARLSON, T. B. Context for comprehension.In J. Long and A. D. Baddeley (Eds.), Attentionand performance IX. Hillsdale, N.J.: Erlbaum,1981.CLARK, H. H., & CARLSON, T. B. Hearers and speechacts. Language, 1982, 58, 332-373.CLARK, H. H., & MARSHALL, C. R. Definite referenceand mutual knowledge. In A. K. Joshi, B. L. Webher,& I. A. Sag (Eds.), Elements of discourse understanding.Cambridge: Cambridge Univ. Press,1981.COHEN, P. R., & PERRAULT, C. R. Elements of a planbasedtheory of speech acts. Cognitive Science, 1979,3, 197-212.F~LLMORE, C. J. Towards a descriptive framework forspatial deixis. In R. J. Jarvella and W. Klein (Eds.),Speech, place, and action. New York: Wiley, 1982.GIBBS, R. W., JR. Your wish is my command: Conventionand context in interpreting indirect requests. Journalof Verbal Learning and Verbal Behavior, 1981, 20,431-444.HAWKINS, J. A. Definiteness and indefiniteness: A studyin reference and grammaticality prediction. London:Croom Helm, 1978.LAKOFF, R. Remarks on this and that. Papers from theChicago Linguistic Society, 1974, 10, 345-356.LYONS, J. Deixis as the source of reference. In E. L.Keenan (Ed.), Formal semantics of natural language.Cambridge: Cambridge Univ. Press, 1975.LYONS, J. Semantics, Voi. 2. London: Cambridge Univ.Press, 1977.MACLARAN, R. On two asymmetrical uses of the demonstrativedeterminers in English. Linguistics, 1980,18, 803-820.NUNBERG, G. The non-uniqueness of semantic solutions:Polysemy. Linguistics and Philosophy, 1979, 3,143-184.OLSON, D. R. Language and thought: Aspects of a cognitivetheory of semantics. Psychological Review,1970, 77, 257-273.PECHMANN, T., & DEtJTSCH, W. The development of verbaland nonverbal devices for reference. Journal ofExperimental Child Psychology, 1982, 34, 330-341.SCHELLING, T. C. The strategy of conflict. Cambridge,Mass.: Harvard Univ. Press, 1960.REFERENCE NOTECLARK, H. H., & SCHREUDER, R. On demonstrative reference.Unpublished manuscript. Department ofPsychology, Stanford University, Stanford, Calif.,September 1981.