The Effect of Communication Modality on Cooperation inOnline Environments

Carlos Jensen1carlosj@cc.gatech.edu

Shelly D. Farnham2shellyf@microsoft.com

Steven M. Drucker2sdrucker@microsoft.com

Peter Kollock3kollock@ucla.edu

1 College of ComputingGeorgia Institute of TechnologyAtlanta, GA 30332-0280 USA

+1-404-894-3152

2 Microsoft ResearchMicrosoft Corporation

Redmond, WA 98052 USA+1-425-882-8080

3 Department of SociologyUniversity of California at Los Angeles

Los Angeles, CA 90095-1551 USA+1-310-825-1313

ABSTRACTOne of the most robust findings in the sociologicalliterature is the positive effect of communication oncooperation and trust. When individuals are able tocommunicate, cooperation increases significantly. Howdoes the choice of communication modality influence thiseffect? We adapt the social dilemma research paradigm toquantitatively analyze different modes of communication.Using this method, we compare four forms ofcommunication: no communication, text-chat, text-to-speech, and voice. We found statistically significantdifferences between different forms of communication, withthe voice condition resulting in the highest levels ofcooperation. Our results highlight the importance ofstriving towards the use of more immediate forms ofcommunication in online environments, especially wheretrust and cooperation are essential. In addition, ourresearch demonstrates the applicability of the socialdilemma paradigm in testing the extent to whichcommunication modalities promote the development oftrust and cooperation.

KeywordsComputer Mediated Communication, Online Interaction,Social Interfaces, Collaboration, Social Dilemma, CSCW.

INTRODUCTIONOne of the most consistent and robust findings in thesociological literature is the positive effect communicationhas on cooperation and trust [9]. When individuals are able

to communicate, cooperation increases significantly. Thereare however many open questions. How does the choice ofcommunication modality influence this effect, and howsignificant are the differences between different forms ofcommunication? These are important questions fordesigners of collaborative online environments.The research area we draw upon is the multi-disciplinarywork on social dilemmas. Social dilemmas are situations inwhich a reasonable decision on an individual level leads tocollective disaster, that is, a situation in which everyone isworse off than they might have been otherwise. Models ofsocial dilemmas capture this tension between individual andcollective outcomes, and can therefore be used as a verypowerful and broadly applicable probe to assess the level ofcooperation and trust in a group. Since the 1950s, a largeresearch literature has developed in this area (for reviews,see [9, 10, 11]).There has been surprisingly little work that has appliedsocial dilemma models to online interaction. One recentexception is a paper by Rocco [12] which showed that face-to-face interactions increased cooperation in subsequentonline interactions. Further, despite knowledge of thepositive effects of communication on levels of cooperation,little is known about which aspects of communication andits medium are responsible for these effects.There is a large literature of work examining several modesof communication and their relative effects on taskperformance [4, 5, 15, 16], especially in the CSCW andvideo-conferencing domains (for an overview see [6]).However, these studies have not specifically examined theeffect of media on the development of trust andcooperation.In most studies, communication has been used as a generalterm, without attempting to distinguish the various effectsof different modalities. A recent survey [14] argued thatthe salutary effects of communication are largely limited toverbal discussions. Written communication was not foundto have a significant and consistent effect on cooperation

levels in groups. However, the evidence in this review wasindirect, and none of the studies discussed attempted toactually compare different communication modalitiesagainst each other.Our hypothesis was that more immediate forms ofcommunication (forms of communication producing aheightened sense of social presence, for instance face-to-face or voice) would prove more effective in promotingcooperation than less immediate forms such as text chat.The sociological literature supports this hypothesis, as docasual observations.Technology coupled with bandwidth limitations havecreated a multitude of communication forms that are hard toevaluate. Is low quality video more conducive tocooperation than high-quality still images, and how doeither compare to the use of 2D or 3D avatars? If any ofthe above were available with text-chat or text-to-speech(TTS), would the combination be more effective than voicecommunication alone?Given a specific domain or application, the mostappropriate form of communication can often bedetermined through traditional user testing, looking at suchvariables as task performance or user preference. Choosingthe right communication modality is crucial, not only out oftechnical considerations such as bandwidth, but also toencourage and support the desired activities.ICQ* and NetMeeting are both examples of popularInternet communication tools. These two tools aredesigned for different audiences, and the choice ofcommunication modality is an integral part of that designdecision. ICQ supports lightweight, informalcommunication through a more anonymous and non-invasive text channel. NetMeeting on the other handsupports a more intimate form of communication throughthe use of voice and video.The present research's examination of communicationmodality may also be applicable to the domain of electroniccommerce which relies on establishing a trustingrelationship between strangers. How can we makenegotiation between prospective trading partners simplerand more transparent? Which forms of communicationlend themselves well to the development of trust, andperhaps equally important, which do not? As consumers, itis also important for us to know which forms ofcommunication make us overconfident, or vulnerable todeception.The unique contribution of this study is to examine fourcomputer mediated communication modalities in a carefullycontrolled experimental setting, and use quantitative modelsof cooperation and competition that are based on several

* Available at http://www.icq.com Available at http://www.microsoft.com/windows/netmeeting/

decades of research. We examined the most common formsof online interaction: no communication, text-chat andvoice. We also examined TTS communication to try togain some insight into the differences between text andvoice communication.The results of this study are important both theoreticallyand practically. Theoretically, this investigation helps toexplain the fundamental dynamics of cooperation in onlinesettings. Practically, it may lead to concreterecommendations on the use of different communicationmodalities, and how limited bandwidth could be best usedin order to encourage trust and cooperation.

METHODOLOGY

System DesignFor this study we used a continuous, iterated, dyadic (two-person) Prisoners Dilemma. The continuous nature of thegame allowed for degrees of cooperation or defection totake place. By making the game iterative, relationshipswere allowed to evolve over time, negotiations to takeplace, and trends to develop.Pre-existing relationships, no matter how brief, greatlyinfluence future interactions, as demonstrated by the workdone by Rocco [12]. Therefore, we decided to focus ourefforts on studying the development of relationships, ratherthan how they change with the use of different mediums.We decided to pursue dyadic trials as opposed to largergroups for logistic reasons, organizing trials with twosubjects is much simpler than doing so with four or five.The Prisoners Dilemma is the most commonly used 2-person social dilemma. The game captures the key tensionsbetween individual and collective outcomes: There is astrong temptation to behave selfishly and exploit thepartner, but both persons are hurt if they behave selfishly.What defines the Prisoners Dilemma is the relative valueof the four outcomes (see Table 1). The best possibleoutcome for an individual is defecting while the otherplayer cooperates (termed DC). The next best outcome forthe players as a group is mutual cooperation (CC) followedby mutual defection (DD). The worst outcome is the casewhen one cooperates while the other player defects (CD).Thus in a Prisoners Dilemma: DC>CC>DD>CD.

IIC D2 3

C 2 0I 0 1

D 3 1

Table 1: Classic Prisoners Dilemma

I and II designate Player I and II. Cand D designate cooperation anddefection respectively. Player Isoutcomes are in bold. In our design,degrees of cooperation is possible.

During the course of the game, subjects were allowed tocommunicate with each other using one of four forms ofcommunication; no communication, text-chat, TTS andvoice (via speakerphone). All other factors were keptconstant across the four cases. The game itself was built ontop of an IRC-like communication channel. The otherplayers contribution (points given) was kept hidden untilboth finished the turn when they got a turn total. Acontroller-bot kept track of the running score for eachplayer, which was kept hidden until the end of the game.Communication between the players was not filtered in anyway. In the text chat condition, the client was divided intotwo parts, one housing the game itself, and the otherhousing a standard chat interface, including a history of thesubjects conversation.TTS was implemented through the publicly availableMicrosoft Speech API 4.0. The voice used in all cases wasthe default, slightly feminine voice. While gender has beenshown to produce biases, it was judged to be the mostunderstandable voice by pre-test subjects. The interface forthe TTS case was similar to that of the text case, except thatthe text messages and the history were hidden from theuser. This was done to force the user to rely exclusively onthe TTS technology. The subjects had their own messagesread back to them in order to inspire greater confidence inthe system. For the voice case, we had a speakerphonesystem in place and used only the game portion of theinterface.

Game RulesThe particular type of Prisoners Dilemma we used was acontinuous version of the game in which degrees ofcooperation were possible: Each turn the two players wereallocated 10 points and given a choice of how many points(from 0-10) they wished to contribute to their partner. Anycontributed points were doubled and given to the partner.Therefore the situation has the structure of a Prisoner'sDilemma: The greatest possible return comes from keepingall of one's points while the partner contributes all 10 points(DC=30 points - the 10 original points plus the 20 pointsfrom the partner's doubled contribution). However, if bothactors followed this strategy each will end up with only 10points (DD - having contributed none to each other) ratherthan the 20 points each would receive if they bothcontributed all their points (CC).In order to promote a high level of motivation (and risk),the subjects compensation was tied to their final score.Those attaining near perfect cooperation or those whoconsistently convinced the other player to contribute morethan they did themselves, earned a piece of software of theirchoice. Lower scores resulted in less valuable prizes,culminating at the lowest score levels with a Frisbee or pen.

Available for from http://www.microsoft.com/iit/

Before the game, the subjects were informed that theirperformance was linked to their final reward. The subjectswere not told how many points were needed to reach thedifferent prize tiers.The two players could see the amount each person hadcontributed on the previous round, as well as that roundsoutcome for both players. To minimize the effect of end-game conditions the subjects were told that the game wouldlast for approximately 120 rounds. All the games endedafter 96 rounds, giving the players a warning to this effecton turn 95. This was done in order to test for the presenceof an end-game condition without tainting the rest of thesequence.

SubjectsThe subjects were paired randomly and then randomlyassigned to one of the four communication categories.They did not meet each other before, during, or after theexperiment. Great care was taken to present the othersubject in as neutral a language as possible, avoiding allterms such as partner or opponent. This was done in orderto preserve the tension between the players without pittingthem against each other. For the same reasons, we did notplace any restrictions on topics of conversation. Subjectswere allowed to negotiate freely or discuss their private lifeif they so chose.A total of 90 adult subjects played the game using one ofthe four communication modalities. Our subject populationwas very diverse, the subjects ranged from 19 to 58 years ofage, averaging at 40. The occupations of the subjectsranged from being retired, to engineers, police officers orstudents. Prior to running the experiments, the subjectscompleted a tutorial explaining the rules and how to use theprogram. As part of this tutorial they were asked tocomplete 4 questions in order to demonstrate theirunderstanding of the game.After the experiment, subjects filled out a questionnairewith standard questions to rate among other things theirunderstanding of the rules and motivation. This was donein order to exclude the subjects who did not understand thegame and those who did not take it seriously enough.Two dyads were excluded because one member reportedthat they did not have a clear understanding of the game.Three other dyads were excluded when it became apparentfrom their communication that they had fundamentallymisunderstood the game. All 3 of these pairs believed theequation CD+DC>CC+CC to be true. Every other turnthey would alternate defection and cooperation, believingthe average of this strategy to be better than continuedmutual cooperation. This elaborate strategy requiredtremendous coordination between the two subjects, as wellas demonstrating full cooperation and trust. Unfortunately,this strategy resulted in a less than optimal score, which

would have unduly skewed the average scores if notremoved.Four dyads were excluded because one member reportedthat they were not motivated to earn as many points aspossible. Three additional dyads were excluded from theanalysis because of their refusal to use the communicationmodality offered to them. All told, 12 dyads were excludedfrom the study.The present study had an unexpectedly high exclusion rate.While we expected to encounter both lack of motivation,and lack of understanding of the rules, we were surprised bythe high percentage of our participants who did notunderstand the rules. Most prisoners dilemma studies usecollege students for their study population, a fairlyhomogenous and intelligent segment of the population. Asstated earlier, our population was much more diverse interms of age and background. For many of our participants,the task was too abstract. They were simply intimidatedand confused by the mathematical nature of the task. Theycould complete the pre-game quiz with the support of thetutorial, but were unable to use this knowledge in the game.After excluding the invalid data, we were left with a total of66 subjects, or 33 dyads: 9 dyads in the non-communicationcase, 9 dyads in the text chat case, 7 dyads in the TTS case,and 8 dyads in the voice case.

RESULTSWe expected that the form of communication would have asignificant effect on the level of cooperation between thedyadic pairs. The more immediate forms of communicationwere expected to be more conducive to the development oftrust and cooperation. A dyadic pair exhibited the highestdegree of cooperation (CC) by exchanging all 10 of theirpoints every round. Table 2 and Figure 1 illustrate thatform of communication does affect average contributions asexpected. An omnibus test of condition, using a between-subjects analysis of variance (ANOVA), shows that type ofcommunication had a statistically significant effect (F(3,29) = 3.42, p < .04).

Table 2: Mean dyadic contribution as a function of the mode ofcommunication. A mean of 10 would indicate perfect cooperationbetween the dyadic pairs. Mean subscripts (abcd) indicate which othermeans are at least marginally significantly different (p < .09).Dyads in the voice condition showed the greatest levels ofcooperation. Most dyads using voice communicationexhibited almost perfect cooperation. Planned comparisons

show that dyads in the voice condition on averagecontributed significantly more than dyads in the textcondition (F(1, 15) = 5.82, p < .03) and the nocommunication condition (F(1, 15) = 7.69, p < .02). Thedifference in average contribution between the voicecondition and the TTS condition was marginally significant(F(1, 13) = 3.50, p < .09).

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Figure 1: Mean dyadic contribution as a function of mode ofcommunication. A mean of 10 would indicate perfect cooperationbetween the dyadic pairs. Error bars represent standard deviations.

Dyads also tended to be more cooperative in the TTScondition than in the text and the no communicationcondition. Dyads in the TTS condition contributedmarginally significantly more than the dyads with nocommunication (F(1, 14) = 3.66, p < .08). The differencein contributions between TTS and text conditions was notsignificant (F(1, 14) = 2.13, p < .17), however the trend isin the predicted direction and could reach statisticalsignificance with a larger number of dyads. That peopleshowed greater levels of cooperation in the TTS conditionthan in the text conditions indicates that voice affectscooperation for reasons other than the differences in thesemantic content of text versus speech, and for reasonsother than the nonverbal information communicatedthrough personal voice, such as intonation and gender.While dyads in the text condition on average contributedmore than dyads with no communication, the difference wasnot significant (F(1, 16) = .37, ns). Dyads showed a muchhigher variability in the level of cooperation in the textcondition and the no communication conditions than in theTTS or the voice conditions. A better understanding of thenature of the greater variability in the no communicationand the text chat condition can be gained through anexamination of histograms of the scores as seen in Figure 2.In the no communication condition, people tended to fallinto either a pattern of no cooperation, or completecooperation. People in the chat condition showed a rangeof levels of cooperation. In the TTS condition and thevoice condition people tended to be at least somewhatcooperative.In the no communication condition, the bi-modaldistribution was often a result of the players' first few turns

Mode ofCommunication

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A. None 9 5.3cd 4.2B. Text Chat 9 6.4d 3.5

C. Text-to-Speech 7 8.4ad 1.4

D. Voice 8 9.4abc 0.2

in the game. Players that trusted each other from thebeginning (giving large sums from the start) generallycontinued cooperating throughout the game. However,when players held back in the beginning, their level ofcooperation deteriorated quickly. While players tested eachother across all cases by holding back occasionally, thisbehavior tended to deteriorate much more quickly in the nocommunication condition.

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Figure 2: Distribution of average contributions for each mode ofcommunication.

An analysis of contributions over time (see Figures 3 and 4)suggests that subjects did not initially cooperate fully witheach other, but in conditions that allowed communicationachieved a degree of cooperation that was greater than theirinitial level. A multivariate analysis of variance on 19averaged blocks (see Figure 4), shows that there was asignificant quadratic trend (F(1, 29) = 5.14, p < .03).Figure 4 shows that the quadratic trend has the shape of aninverted U, and an analysis of the trends shows that theshape of the trend was not affected by condition (F(3, 29) =.46, ns). This indicates that subjects tend to build trustearly in the game, but that said trust tends to deteriorateover time, across all conditions. Again, this is consistentwith what is found in the literature [2, 9, 12]. Anexamination of Figure 3 suggests that there was an end-game effect, replicating past research [9] that shows thatcooperation will drop at the end of the game in a selfishattempt to maximize the final score. However, acomparison of the last round of points and the preceding

rounds of points shows that this difference is notstatistically significant.

Average Contribution per Turn

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Figure 3: Average contribution across game rounds broken down bymode of communication.

Average Contrubution in Blocks of 5

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Figure 4: Average contribution across game rounds in blocks of five,broken down by mode of communication.

During the course of the game the subjects tended to varytheir contributions across rounds (see Figure 3). The meanstandard deviation for each dyad was 1.13, indicating thatdyads tended to vary their contributions across rounds byadding or subtracting a point or two from their average.We argued that people achieved greater levels ofcooperation in the voice and text conditions because theywere able to achieve greater levels of trust. To address

whether people subjectively felt more trusting of the otheracross conditions, subjects were asked a series of questionsin a post-experiment questionnaire. Subjects were asked torate the other player on characteristics related to likeability(likable, kind, friendly, and warm), trustworthiness (honest,fair, trustworthy, and sincere) and intelligence.As seen in Figure 5, people felt they liked and trusted theother player more if they were able to communicate withthat person. An ANOVA shows a marginally significanteffect of condition on ratings of the other playerslikeability (F(3, 59) = 2.44, p < .08) and trustworthiness(F(3, 59) = 2.54, p < .07). Only in the voice condition didpeople tend to rate the other player as more intelligent.There was a significant effect of communication modalityon ratings of the other players intelligence (F(3, 61) =2.79, p < .05).

Figure 5: Evaluation of interaction partner

DISCUSSIONConsistent with sociological literature for off-lineexperiments, voice communication was found to have anextremely powerful effect on peoples tendency to trust andcooperate with each other. We found statisticallysignificant differences between the voice communicationcondition and both the text-chat and the no-communicationcondition in predicting cooperation. We found marginallysignificant differences between voice and TTS, andbetween TTS and no-communication.An examination of how people evaluated their partnerssuggest that they had a more positive image (likable andtrustworthy) of those with whom they could communicate.In addition, people felt that their partners were moreintelligent when they could communicate with them byvoice. This effect could be caused by the differing amountsof time that it took for people to communicate in each of themodalities. Past studies have shown a direct relationship

This analysis was performed on ratings of the other player at theindividual level rather than at the dyadic level. Dyadic effects werecontrolled for by entering the dyad as a covariate in the analysis.

between delays in communication and perceived levels ofintelligence [13].One possible explanation for why we did not findstatistically significant differences between TTS and text-chat is that our sample size was too small. A poweranalysis suggests that the effect could reach significancewith approximately double the number of dyads (15 in eachgroup as opposed to 8). Also, consistent with previousfindings in the sociological literature, we did not findstatistically significant differences in cooperation betweennon-communication and text-communication modes. Thelack of an effect may be due to the high variance in the twoconditions. An examination of histograms of scores foreach condition suggests that people tended to lapse intoeither full cooperation or full defection in the nocommunication condition, which greatly increases thevariance of the condition.Though our results are consistent with previous findings,we were nevertheless surprised by the lack of statisticallysignificant differences between the text-chat and non-communication conditions. Strategic discussion was aprimary topic of conversation in a number of the trials(approximately 80% of the dyads who could communicatediscussed strategy), but while discussion was followed byrobust cooperation in the voice condition, it was not asreadily followed by cooperation in the text-chat condition.We were also surprised by the relative difference betweenTTS communication and text-chat. Initially we expected nodifferences between TTS and text, because TTS containssimilar semantic content to the text case, but little of thepara-verbal information found in voice. In fact, since TTSmight be artificially lacking cues that people use inpredicting the veracity of utterances, we felt that theremight be a negative effect associated with using TTS.There are several possible explanations for the higher levelof cooperation in the TTS condition over the text-chatcondition. Perhaps the experience of hearing a voiceenhanced peoples perceptions of social proximity.Another possibility is that without an available history suchas found in text-chat; subjects were forced to pay greaterattention to the other player, hence increasing their sense ofsocial presence.The fact that the TTS condition gave positive resultssuggests that it could be used in other situations. Perhapswe could improve on voice or video interaction bymodifying the voice or aspects of the appearance to matchthe preferences or biases of the other participant. Forinstance, instead of always using a gender-neutral voice, wecould appeal to a users sense of group identity by using anappropriately gendered TTS voice. This of course quicklyraises a number of ethical questions and concerns.One of the problems with the design of our experiment wasthat the voice condition quickly reached a ceiling effect ofperfect cooperation. This lack of resolution prevented us

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from getting a clearer contrast between voice and the otherconditions. If more immediate forms of communicationsare to be examined, we will need to create a situation with ahigher sense of risk and temptation to defect. We discusspossible ways to do this in the future work section.Finally, while the voice condition did achieve fairlyuniversal cooperation, a number of subjects showed somereluctance to using this mode of communication. Thesesubjects reported being uncomfortable with the level ofintimacy associated with voice communication, and saidthat they would have been more comfortable with text-chat.For these subjects, a less intimate mode of communicationmight well have produced better results than voice.

FUTURE WORKIn the future, we would like to run a larger number ofsubjects through these tests. With a larger population itcould be possible to show the benefit of text over nocommunication, as well as see a clearer distinction betweenthe other forms of communication. We would like toexamine a number of additional modalities, including videoat various resolutions and frame-rates, the use of both 2Dand 3D avatars and asynchronous communicationmodalities such as voice mail and email.The Prisoners Dilemma can easily be extended to include alarger number of participants in every game. Not only dothese N-person social dilemmas model an important class ofinteractions (group dynamics) not captured in the 2-personsituation, they also create a significantly more competitiveenvironment. This would help remove the ceiling effect oftotal cooperation we observed in the voice condition, andperhaps allow for a difference between voice and morepersonal forms of communication (e.g. video and face-to-face) to be observed.The social dilemmas are very sensitive to individual quirksand personality traits. To truly validate the results, a largenumber of subjects is needed. By using the World WideWeb, large online experiments could become significantlyeasier to do. Such an approach would also be valuable fordoing cross-national experiments, helping to determinewhich effects are related to culture. We are currentlyworking on the design of such a system together withsociologists from a number of universities around theworld.Despite the simplicity of the task, a number of subjectswere unable to determine what the optimal game strategywas (CC). These subjects cooperated to the best of theirabilities, but did so in a sub-optimal fashion (most of thesebelieving DC+CD>CC+CC). Some subjects were thrownby the simplicity of the task, believing that there had to be atrick, a secret strategy or hidden motivation behind theirtask. Many subjects also remarked on how boring the gamewas, some stopped cooperating in an attempt to make thingsmore interesting, and one pair went as far as to improvise a

game of tick-tack-toe using the numeric keypad. We mightbe able to solve both problems by transforming the gamefrom an abstract problem solving exercise into somethingmore tangible, for instance some form of a card or videogame.Further experiments need to be done on the sensitivity ofthe technique for comparing different communicationmodalities. We found that this method was very sensitiveto factors such as wording and the perceived level of riskamong the participants. If the stakes are low, people have atendency to take higher risks and be less selfish. As thestakes get higher, the inclination towards selfish behaviorincreases. An interesting question is how to encourage ahigh sense of risk in a WWW version of the game.We would like to start looking at factors other thancooperation, for instance the development of empathy, orhow the medium affects the ability to determine identity.From our current results it seems that people might beprone to making assumptions for which they have littlebasis or no for in the TTS case. In face-to-face interactions,many people believe that they can judge a persons honestyby simply looking into their eyes. Are people more proneto making such assumptions with some forms ofcommunication than with others, and if so, how does themedium affect which assumptions are made?A final avenue of research is extending our results to pre-existing relationships. While there are many situationswhere we deal with relative strangers, the existingrelationship addresses an important set of interactions. Pre-existing relationships have a very significant effect onfuture interactions, even in high-risk situations [12]. Bystudying how the medium affects existing relationships, ourresults could be more easily applied to CSCW andgroupware applications.

CONCLUSIONWe have demonstrated a technique for the quantitativeassessment and comparison of the effect of different formsof communication on the development of trust andcooperation. Consistent with the sociological literature,voice communication was found to have an extremelypowerful effect in fostering trust and cooperation. Alsoconsistent with previous results, text chat was not found tohave a statistically significant effect beyond that of nocommunication. In our experiments, this may be caused bythe high variance of both the text and the non-communication cases.As expected, more immediate forms of communicationshowed a greater impact on the development ofcooperation. The biggest surprise of this study was thedifference between TTS and text-chat. While there was nostatistically significant difference, the average contributionwas 2 points higher in the TTS case. This indicates that

TTS technology could have the potential to positivelyinfluence computer-mediated communication.The social dilemma methodology is a robust and widelyused tool in the social sciences. By leveraging thistechnique we are better able to analyze and evaluate themany factors affecting social interactions.We believe that our methodology can be adapted to analyzea wider array of social factors. By going beyond trust andcooperation, our method could become a valuable general-purpose tool in the study of computer-mediatedcommunication.

ACKNOWLEDGEMENTSWe wish to thank Motoki Watabe for his assistance in thedata analysis, as well as the Virtual Worlds group atMicrosoft Research for their support.

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