mediating group dynamics through - stanford hci...

Published by the IEEE Computer Society 0272-1716/06/$20.00 © 2006 IEEE IEEE Computer Graphics and Applications 65

Interacting with Digital Tabletops

We encounter tables in a variety of situa-tions in our everyday lives—at work,

school, and home as well as in restaurants, libraries, andother public venues. The ubiquity of tables results fromthe utility of their affordances. Tables’ horizontal sur-faces permit the placement of objects, and their largesurface area affords the spreading, piling, and organiza-tion of these items. Chairs afford sitting and relaxing,making work around tables leisurely and comfortable.Perhaps most importantly, tables allow face-to-face col-laboration among a small group of colocated individuals.One of the primary reasons people perform tasks attables is because of the social affordances they provide.Consequently, when designing next-generation interac-tive table technology, this technology’s impact on groupdynamics is a key issue. The effect of group dynamics onthe use of the technology likewise has important bear-ing on interactive table design.

Our tabletop research efforts at Stanford Universityhave focused on how tabletop user interfaces (UIs)might respond to and even influence a user group’ssocial dynamics. In this article, we provide an overviewof four projects:

■ Multi-User Coordination Policies (a joint researcheffort with Mitsubishi Electric Research Laboratories),

■ cooperative gesturing, ■ educational tabletop interfaces, and■ Shared Interfaces for Developing Effective Social

Skills (Sides).

Multi-User Coordination Policies explore how table-top interfaces can react to breakdowns in group socialdynamics to avoid resulting workflow interruptions.

Cooperative gesturing is an interaction techniquethat can mitigate negative social dynamics (for exam-ple, by drawing attention to actions that potentially dis-rupt other group members’ activities) and encouragepositive group dynamics, such as participation andsocialization.

Our work on educational tabletop interfaces focuseson how subtle variations in tabletop UIs can achieve spe-cific pedagogical goals, such as minimizing the free-rider problem during small-group activities andfacilitating collaborative problem solving. We have eval-uated several design variations related to these educa-tional concerns.

Additionally, we discuss our work on Sides, whichexplores how the design of an interactive tabletop com-puter game can promote desired group interactionsamong adolescents diagnosed withAsperger’s syndrome.

Through all these projects, welearned that many aspects of groupdynamics, including conflict, aware-ness, participation, and communica-tion, can influence and be influencedby interactions with a shared table-top display.

All of the projects described use Mitsubishi’s DiamondTouch,1

an 85.6-cm by 64.2-cm touch-sensitive surface. Up to four userssit on conductive seat pads. Thedevice identifies which usertouched at which point based oncapacitive coupling. All four usersmay interact simultaneously if theywish. DiamondTouch’s user-iden-tification feature is key to our inter-face prototypes’ functionality. However, even withouta DiamondTouch surface, user identification can occurusing a variety of current and emerging technologies,including computer vision and face recognition, bio-metrics, or fingertip proxies (such as styli or mice)with user-specific signals or tags. All of the projectswe describe also use Mitsubishi’s DiamondSpin table-top interface toolkit.2 DiamondSpin is a Java toolkitthat simplifies developing tabletop UIs by providing apolar-coordinate-based programming model, which

A Stanford University researchgroup explores how designalternatives for tabletopinterfaces can impact groupdynamics to promote effectiveteamwork. They built andevaluated a series of novelprototypes that explore Multi-User Coordination Policies and cooperative gesturing,encouraging equitableparticipation in educationaltasks and supporting socialskills development for special-needs populations.

Meredith Ringel Morris, Anthony Cassanego,Andreas Paepcke, and Terry WinogradStanford University

Anne Marie PiperMicrosoft

Anqi HuangHarvard University

Mediating GroupDynamics throughTabletop InterfaceDesign


66 September/October 2006

allows flexible specification of objects’ orientationson the horizontal display.

Coordination policiesOur exploration of the interplay of tabletop UI design

and group dynamics began with our observations ofundesirable group dynamics during tabletop use. Thestatus quo for colocated groupware is to assume thatsocial protocols (standards of polite behavior) are suffi-cient to coordinate a group of users’ actions. However,prior studies of groupware use have found that socialprotocols do not always provide sufficient mediation. Forinstance, Greenberg and Marwood3 observed that socialprotocols cannot prevent many classes of conflicts,including those caused by accident or confusion, unan-ticipated side effects of a user’s action, and interruptionsor power struggles. Examples of such breakdowns werereported in Izadi et al.’s evaluation of Dynamo,4 a large,shared wall display. Studies of Dynamo revealed a prob-lem with overlaps—situations where one user’s interac-tions interfered with another’s, such as when a userclosed a document that belonged to someone else with-out asking first, or when users were concerned thatgroup members might steal copies of their work withoutpermission. Our own observations of a tabletop docu-ment-sharing and annotation application, Mitsubishi’sTable-for-N,2 yielded additional observations of conflictbehaviors, such as a user clearing the screen or quittingthe application while other group members were work-ing, and users grabbing digital documents away fromothers who were using them.

These observations prompted us to conduct two sur-veys to better understand users’ expectations regardingthe outcomes of conflicts when using a shared tabletopdisplay.5 These surveys presented users with a conflictscenario: Users A and B are sitting across from each

other at a table, and B has a document. User A thenreaches across and grabs B’s document. In one survey,the table was a traditional piece of furniture, and thedocument a piece of paper. In the other, the table was aDiamondTouch, and the document was virtual. In eithercase, respondents were asked to list all the outcomesthey could imagine for the conflict described. The sur-vey responses (20 people completed the survey for thepaper scenario, and 27 for the digital scenario) revealedseveral popular envisioned outcomes to the conflicts.We embodied these popular suggestions in our Multi-User Coordination Policies.

Multi-User Coordination Policies6 are software mech-anisms for avoiding and/or mitigating the effects of con-flicts that result from breakdowns of social protocols.Having tabletop interfaces respond to social breakdownsin reasonable, deterministic ways can reduce workflowinterruptions and allow users to focus on the task athand. We developed two classes of coordination poli-cies: policies for global conflicts and for whole-elementconflicts. Global conflicts involve changes that impactthe application as a whole (such as when one user clearsthe screen while others are still working). Whole-element conflicts involve disputed access to a singleobject. The aforementioned survey results influencedthis latter class of coordination policies. We created testimplementations of each of our proposed policies as anextension of the DiamondSpin toolkit.

Example global coordination policies include these:

■ No holding documents. Changes that would impact glob-al state can only succeed if no other group members arecurrently touching digital documents on the tabletop.

■ Voting. Voting widgets appear in response to proposedglobal state changes, and group members can vote foror against the change.

1 The duplicate coordination policy reacts to a whole-element conflict by replicating the contested item.

2 The tear coordination policy reactions to a whole-element conflict by mimicking paper-based interactions to draw attention tosocial breakdowns.

■ Privileged objects. Global changes can only be madefrom a special menu. The use of a special interfacemechanism for these changes is intended to drawattention to the potential for these reserved actionsto impact other group members.

Example whole-element coordination policies includethe following:

■ Duplicate. When two users both try to grab the samevirtual document, it automatically duplicates itself(see Figure 1).

■ Tear. A contested document breaks into two pieces,drawing attention to a social breakdown and encour-aging negotiation for reassembly (see Figure 2).

■ Rank. A higher ranking user can always take docu-ments from lower ranking users (for example, ateacher with students).

Duplicate, tear, and rank are examples of reactivepolicies, which respond to a breakdown with a deter-ministic behavior. Our policies also include proactiveoptions, which let users keep their documents in a pri-vate state to prevent conflicts (such as document grab-bing) from occurring in the first place. One example ofa proactive whole-element policy is sharing, which letsusers dynamically transition a document between a pub-lic state (where there are no limits on who can accessthe item) and a private state (where tabletop identifica-tion features enforce access only by the owning user).

We have implemented and evaluated four interactiontechniques to allow fluid transitions between public andprivate document access: release, relocate, reorient, andresize.7 The release technique uses a hand-off gestureto transfer document access permissions, while the relo-cate technique ties access to tabletop location: docu-ments located in the center are publicly accessible, whiledocuments located in a user’s personal space are private(see Figure 3). Reorient uses a document’s orientationto determine access rights (for example, documents fac-ing their owner are private, but turning them to face oth-ers makes them accessible). With the resize interaction,when a user enlarges documents, those documents thenbecome public.

Coordination mechanisms beyond social protocolscan play a valuable role in tabletop groupware. In addi-tion to preventing conflicts that might arise due to con-fusion or discord, such policies also help ensure that

groupware has deterministic, predictable responses tomultiuser interactions.

Cooperative gesturesOur work on Multi-User Coordination Policies led us

to consider other interaction techniques that couldpotentially mitigate undesired aspects of group behav-ior by increasing group awareness of important interac-tions and encouraging a sense of involvement andtogetherness. This line of inquiry led us to design coop-erative gestures: interactions where a tabletop systeminterprets the gestures of more than one user as con-tributing to a single, combined command.8 This inter-action technique trades off some performanceefficiency for the benefits of enhanced collaboration,communication, awareness, and/or fun. These bene-fits might indirectly improve efficiency by reducingerrors or miscommunications, although we have notyet formally explored this possibility.

Several motivating scenarios exist for cooperative ges-turing techniques. Interactions that require explicitcoordination among multiple users can increase partic-ipation or collaboration among group members—thismight be particularly relevant for educational activitiesfor children or for special-needs groups (see the “Edu-cational interfaces” and “Interfaces for special-needspopulations” sections for more detailed discussions ofthese issues).

Another application of invoking a group gestural com-mand is for potentially disruptive system commands. Inthis scenario, the cooperative gesture serves to increasegroup awareness about irreversible program actions.

Cooperative gestures can also facilitate reach on largesurfaces, provide a means for implicit access control ofvirtual tabletop items, or provide a fun and sociable feelto entertainment-oriented applications. Some of theseapplications of cooperative gesturing relate to our previ-ous work on Multi-User Coordination Policies—usingsuch a gesture to increase awareness of important systemevents could be one means of implementing a global coor-dination policy, while cooperative gestures for access con-trol are a possible mechanism for a whole-element policy.

To explore the properties of cooperative gesture inter-action techniques, we developed CollabDraw. Collab-Draw is a tabletop art application that lets groups of twoto four users create drawings and photo collages. A setof 16 gestures controls CollabDraw: 5 single-user ges-tures and 11 cooperative gestures. CollabDraw recog-

IEEE Computer Graphics and Applications 67

3 The relocate interaction technique is one means of implementing a sharing coordination policy. Users can transition a documentfrom a privately accessible state to public availability by moving it from their personal region into the table’s shared, central region.

nizes gestures through a combination of machine-learn-ing techniques and heuristic rules.

One gesture that CollabDraw recognizes is a pilingmotion made with two hands (see Figure 4), which col-lects any photos between those hands into a single pile.However, the effect is amplified when all four membersof a group simultaneously perform this gesture—thesystem combines all photos on the table, regardless ofwhether they are between anyone’s hands, into a singlepile in the table’s center. This illustrates one class ofcooperative gestures, additive gestures, which have bothsingle-user and cooperative interpretations.

Another additive gesture in CollabDraw’s repertoireis the action for erasing digital ink, which involves rub-bing the open palm of the hand back and forth over themarks to be erased. When all four group members simul-

taneously perform the erase motion, the result is to clearall ink on the entire tabletop, rather than only the inkdirectly underneath the users’ hands. In both these cases,the additive effect (organizing or clearing the table’s con-tents) could potentially disrupt users’ work activities ifinvoked unexpectedly by a teammate. Thus, we requirethe group’s input to collectively trigger those events.

The modify ink gesture interprets the actions of morethan one user to determine the appearance of the digi-tal ink that can be drawn on the tabletop. For example,one user’s finger determines where the ink is drawn,while another user can control the thickness of thedrawn line by placing two fingers on the table’s surfaceand varying the distance between them (see Figure 5).This gesture’s design is intended to increase users’ senseof team involvement during the activity by couplingusers’ input in a creative and entertaining manner.

Exiting CollabDraw also requires a cooperative action,to prevent accidental invocation of this command whileother group members are still drawing. The exit gesturerequires all group members to hold hands, and the userat the end of this chain touches the table’s surface (seeFigure 6). CollabDraw recognizes hand-holding byexploiting DiamondTouch’s special properties: Whenany one member of a hand-chain touches the table’s sur-face, the electrical coupling between the users causesthe device to sense that all four group members havesimultaneously pressed at a single point.

Our evaluation of cooperative gesturing involvedseven pairs of subjects, who were trained on each of thegestures. Subjects then had to recreate a target drawingusing the gestures they had learned and provided ques-tionnaire feedback about their experience. This evalu-ation highlighted several lessons relevant for designingfuture iterations of cooperative gesture interfaces:

■ the need to develop techniques to avoid accidentalinvocation of cooperative actions by coincidental,simultaneous performance of single-user gestureswith additive meanings;

■ the impact of proxemics (intimacy levels) on gesturedesign; and

■ the potential tedium of using cooperative interactionsfor frequently invoked system commands.

A more complete description of the other gestures thatCollabDraw recognizes as well as details on our evalu-ation procedure and results are available elsewhere.8

Based on our experiences designing, implementing,and evaluating an initial set of cooperative gestures, wearticulated some important axes of the design space forthese interactions. The seven design axes we identifiedare symmetry, parallelism, proxemic distance, additivity,identity awareness, number of users, and number of de-vices. An interesting avenue for future work is to analyzethe impact of these design axes on cooperative gestures’learnability, memorability, usability, and naturalness.

Our initial experiences with cooperative gesturingsuggest that integrating this interaction technique intotabletop systems can emphasize particularly importantapplication events while promoting a highly social inter-active experience.



4 When all four group members simultaneously perform the “neaten”gesture, the result is the cooperative gesture for “organize table.” All pho-tos on the table are swept into a single, central pile. Because the sameaction has valid single-user and multiuser interpretations in CollabDraw, itexemplifies an additive-effect gesture.

5 CollabDraw adds a creative aspect to drawing by making it a cooperativeaction, as shown in this modify ink gesture. The left-side user’s finger speci-fies the (x, y) coordinates where ink will appear, and the right-side user’sfingers specify the resulting stroke’s width.

Educational interfacesCoordination policies and cooperative gestures aim

to mitigate the effects of poor team coordination. Ournext project tackled the issue of group dynamics andtabletop displays with a more ambitious goal: to active-ly encourage desired group work styles through UIdesign. The importance of collaboration in small-groupwork and methods for facilitating effective group work,specifically through group problem-solving tasks, is aprominent research topic in the education field. Smallgroup work is particularly valuable in the foreign-lan-guage-learning domain, where peer-to-peer interactionprovides important opportunities to practice conversa-tional skills. Interactive table technology is an excitingnew platform for educational activities because it com-bines face-to-face small group work with the benefits ofdigital media for providing students with immediatefeedback about their progress. Such technology alsoallows flexible adaptation of content for different top-ics and skill levels.

As part of our efforts to understand how we can designinteractive table applications to support educationalgroup work, we conducted interviews with foreign lan-guage teachers at our institution. These teachers indicat-ed that the free-rider problem—someone not partici-pating as much as other group members—is a key con-cern when allowing students to work in groups. Thus, wechose to explore how we could design tabletop UIs toreduce free riders by increasing participation equityamong group members. In the previous section, we dis-cussed cooperative gesturing, which can lend a social andparticipatory feel to an application by requiring the activeinvolvement of all group members to execute certainactions. Adding cooperative gestures to an educationalactivity could be one means of ensuring participation byall students in a group. However, our evaluation of theCollabDraw system found that excessive use of coopera-tive gesturing could make an activity tedious. Conse-quently, we decided to investigate additional, morelightweight UI designs that might also encourage moreparticipation in tabletop activities for educational tasks.

We created three tabletop language-learning applications with flexible, adaptable structures to fitvarying content:

■ MatchingTable, which lets students match words andphrases with images (see Figure 7);

■ PoetryTable, which lets students create free-form sen-tences from word tiles; and

■ ClassificationTable, which lets students sort vocabu-lary words or sentences into one of four corners of thetable based on various properties (see Figure 8 on thenext page).

We explored four design variations of these applications,to assess the impact on participation equity: feedbackmodality, feedback privacy, interaction visualizations,and spatial configuration.

Feedback modalityTo explore the impact of feedback modality on group

participation during an educational tabletop activity,

we had 32 paid subjects (divided into eight groups offour each) who had taken Spanish-language coursescomplete a series of ClassificationTable activities. Theseactivities used Spanish-language clues describing setsof Latin American countries, to simulate a foreign-lan-guage-learning activity. Subjects were asked to speak inSpanish during the activity.

One variation we explored was the modality throughwhich we provided feedback regarding the correctnessof clue classifications in the Spanish ClassificationTableapplication. We explored two alternatives: visual feed-back (the clues’ text turned either green or red to indi-cate correct or incorrect placement) and audio feedback(either an upbeat or discordant tone was played to indi-cate correct or incorrect placement). We hypothesizedthat audio feedback would increase the amount of con-


6 Exiting CollabDraw requires a cooperative gesture, to prevent accidentalinvocation of this potentially disruptive command. To perform the exitgesture, all users hold hands in a chain and the last user touches the tabletop.

7 Students in one of Stanford University’s English as a Second Languagecourses interact with the MatchingTable, combining English descriptionswith photos of their classmates. The one-eared headsets they wear serveseveral purposes: during some activities, touching words on the tabletopcauses them to be pronounced through the earpiece. The earpiece can alsoprovide individually targeted audio feedback regarding the correctness ofan action. The microphones on each headset gather speaker-volume datathat can optionally be displayed via interaction visualizations.

versation among group members (important forrehearsing a foreign language) by breaking the ice andinserting noise into the environment, making it less awk-ward for students to generate their own noise by talk-ing. Audio feedback should also increase students’awareness of their participation levels because it push-es information to them.

By comparing subjects’ self-assessments of their con-tribution to the activity (in terms of number of clues clas-sified) with logs of actual tabletop interaction, weconfirmed that audio feedback increased subjects’ accu-racy for these estimates as compared to visual feedback.Subjects also conversed more in the presence of audio,rather than visual, feedback, speaking in Spanish during74.3 percent of the session (rather than only 60.8 percent with visual feedback).

Feedback privacyAnother interface variation we explored was whether

feedback regarding the correctness of clue placementin the ClassificationTable activity was conveyed publicly(to the entire group) or privately (only to the groupmember who moved a particular clue). We exploredthese conditions as part of the same experimental ses-sions as the feedback modality variants, with the Span-ish-language-learning content. To explore privatefeedback in the shared environment context, we usedindividually targeted audio feedback via one-earedheadsets. We hypothesized that private feedback wouldincrease participation equity by reducing the potentialfor embarrassment over incorrect answers, and there-by encouraging shy and underperforming students tocontribute more to the activity. We also hypothesized

that private feedback would increase the accuracy ofstudents’ self-assessments of performance by drawingmore attention to their individual contributions.

We found that when subjects received private feed-back, they tended to clearly emphasize positive resultsto the group, via thumbs-up gestures or exclamationsof “Sí,” “Bueno,” and “Yeah!”. Negative feedback wastypically acknowledged more subtly, by a slight headshake or the user moving the incorrect clue back intothe central region without commenting. This lack ofdrawing attention to the negative feedback supports ourdesign motivation for providing such feedback private-ly—to reduce potential embarrassment over incorrectanswers by not pointing them out to the entire group.Likert-scale questionnaire responses confirmed thatusers felt less self-conscious about their performancewhen using the private audio feedback, and their com-ments, such as “I prefer private audio, so I can knowwhat I got correct or incorrect with a sense of confiden-tiality,” echoed this trend. However, subjects’ sentimentswere not strongly reflected in their actions in terms ofclear changes in patterns of participation equity. We sus-pect that the artificial experimental situation might haveimpacted this. That is, subjects’ behavior was not strong-ly influenced by feelings of embarrassment since theywere not in a real classroom situation, and were not like-ly to encounter their coparticipants in the future.

Interaction visualizationsDiMicco et al. explored the impact of a real-time visu-

alization on group participation in a planning task(where participation referred to the amount each per-son contributed to a conversation).9 For the planningtask, DiMicco et al. found that overcontributors spokeless in the presence of the visualization, but that under-contributors did not increase their participation becausethey did not believe the display was accurate.

Inspired by this study, we integrated real-time his-tograms into some versions of our educational tabletopactivities (see Figure 8). The histograms appear on thetable in the region directly in front of each user and canreflect either the number of answers contributed by eachgroup member based on tracking touch interactionswith the table or the amount of time each user has spentspeaking relative to other group members.

We hypothesized that the histograms in our applica-tion would increase participation equity and would havegreater impact than in the setting studied by DiMicco etal. because the histograms should have more credibili-ty to users in the context of a computer-mediated activ-ity. We also altered the design of the visualizations thatDiMicco et al. described to make them more appropri-ate for a collaborative educational activity by having acustomized visualization for each group member(instead of a single visualization for viewing by theentire group). We highlighted the current user’s bar incolor and grayed out the bars representing the otherthree users, so that students would feel they were com-paring themselves more to a group average than com-peting directly against individual group members.

We evaluated the impact of interaction visualizationsin a separate study, completed by 40 subjects divided into



8 This screen shot shows a ClassificationTable activity. Groups of studentswork together to assign each fact to the US president that it describes.Interaction visualizations in front of each user’s seat reflect how many cluesthat student has classified relative to other group members, with the goalof encouraging more equitable distributions of work among group mem-bers. In this example, the yellow user (top) has been most active in classify-ing clues, while the blue user (right) has interacted the least.

three- and four-person groups. Subjects used three vari-ants of the ClassificationTable. Before the experiment,they read articles about past US presidents, first ladies,and Supreme Court justices. Facts from these articleswere then presented as part of the ClassificationTableexercises, to simulate a classroom experience. In onevariant, interaction visualizations showed each user howmany clues they had classified relative to other groupmembers. In another, visualizations showed the amounteach user spoke during the activity relative to everyoneelse in the group, and another variant had no visualiza-tions at all. We hypothesized that the presence of visual-izations showing speaking contributions would result inmore participation equity in terms of amount of conver-sation contributed by each user, while the presence ofvisualizations showing the amount of clues classifiedwould increase participation equityin that domain.

We found that the visualizationsreflecting speech contributionsincreased participation equity amonggroup members in terms of amountof conversation contribution by eachperson (F(1, 2) =3.93, p < 0.05). Theclassification visualizations, on theother hand, did not produce a changein classification participation equityrelative to the other two conditions.Our observations during the sessionsoffer a possible explanation for thisdifference in impact. During the ses-sions with speech visualizations, we noticed that manyusers would engage in filler speech—speech that wasrelated to the activity (such as reading the clues aloud orasking other group members for their opinions), butwhich did not offer a concrete contribution to the activityby suggesting an answer or offering information. Howev-er, these types of filler actions were not possible for theclue classification, where any action would involve a con-crete attempt to make a statement about the answers. Weneed to do further work in this area to determine whetherawareness visualizations can impact contribution in aneducationally beneficial way, rather than only motivatingthe production of filler behaviors.

Spatial configurationWe altered the initial configuration of clues and photos

in our three tabletop activities to explore the impact ofinitial layout on participation. In the “four piles” design,we initially placed all objects (clues, word tiles, photos,and so on) into four random, equally sized virtual pilesnear the four users’ seats around the table’s borders. Inthe “central pile” design, we initially placed all objectsinto a single virtual pile in the center of the table.

We informally explored these spatial configurationvariations as part of the use of our tabletop applicationsin an English as a Second Language course at Stanford.About 20 students from this class used the table duringtwo sessions over the course of two weeks, completingactivities that tied in to the current lessons in their course.

We hypothesized that the four piles design wouldincrease participation equity as compared to the cen-

tralized design by making undercontributors feel moreresponsibility for the items that started out nearest themand by making overparticipators hesitant to reach outand take responsibility for objects that originated nearothers. This hypothesis is in accordance with Scott etal.’s studies of tabletop group work that have found that a table’s central area is considered a group-owned,public space, while the areas directly in front of eachuser are considered personal or private zones.10

Trends in the data collected during the ESL class’s useof the ClassificationTable, MatchingTable, and Poetry-Table applications support our hypothesis that laying outinformation in four piles—one near each group mem-ber, rather than in the center of the table—encouragedmore equitable participation. For each student group,we calculated the standard deviation of the percent of

touch events contributed by eachgroup member, and of the percent oftalking time contributed by eachgroup member. Lower standarddeviations reflect more equitablecontributions among group mem-bers. For each of the three tabletopactivities completed, groups hadlower standard deviations for boththe percent of touch interactionscontributed and the percent of con-versation contributed under the fourpiles condition. However, students’comments on questionnaires distrib-uted after the activities reflected a

potential drawback of the four piles layout, suggestingthat it detracted from the activity’s collaborative feel.

More details about our educational software, testingscenarios, and statistical analyses are available else-where.11 Overall, our experiences in designing and eval-uating educational tabletop groupware indicate thatrelatively small UI variations, such as the modality orprivacy of feedback, the layout of objects on the sharedsurface, or the presence of explicit awareness informa-tion, can produce observable impacts on students’ teamwork styles. The ability of UI design to facilitate specif-ic pedagogical goals presents an exciting, and potential-ly high-impact, area for further research.

Interfaces for special-needs populationsContinuing our theme of exploring the potential for

tabletop interface design to promote positive groupdynamics, we created a tabletop interface for a user pop-ulation for whom social interactions are a particularlyrelevant topic: youths diagnosed with Asperger’s syn-drome (AS). AS is a pervasive developmental disorderand is considered an autism spectrum disorder. Individ-uals with AS have difficulty understanding acceptedsocial conventions, reading facial expressions, interpret-ing body language, and understanding social protocols.These social deficits can lead to challenges in learningeffective group work skills, including negotiation, per-spective taking, and active listening.

Most computer programs for social skills developmentare designed for one user working directly with the appli-cation, and lack the face-to-face interaction found in


The ability of UI design

to facilitate specific

pedagogical goals presents

an exciting, and potentially

high-impact, area for

further research.

authentic social situations. Our contextual inquiry at alocal middle school special education classroom revealeddiscontent with current classroom board games andgroup activities for social skills therapy. Tabletop tech-nologies are more compelling for this user populationthan traditional board games for several reasons:

■ many individuals with AS describe an affinity for tech-nology,

■ computer technology has the ability to enforce basicgame rules (freeing up therapists’ time to deal withhigher level group issues), and

■ computer games have the flexibility to adapt contentand difficulty level.

Tabletop technology is a unique platform for multiplay-er gaming, combining the benefits of computer gameswith the affordances of face-to-face interaction. Wewere particularly interested in exploring how tabletopinterface design could impact group dynamics for this unique user population, who stand to benefit fromsuch systems.

Based on the results of our contextual inquiry process,which involved observing and interviewing studentsaged 11 to 14 with AS in a middle school social skillstherapy class and their therapist, we developed the Sidesgame.12 Sides is played by four students with AS whoare supervised by their social skills therapist (so that heor she can help the students discuss and understandissues that arise during gameplay). The game aims tocreate a path enabling a frog to travel between two spe-cific lily pads (see Figure 9). If this path intersects a vari-ety of insects located on the table, players earn extra

points. The path is constructed from directional arrowpieces; the distribution of different types of arrow piecesamong the four players ensures that they cooperate andnegotiate with each other to construct a valid path.

Sides incorporates several features designed with theparticular social needs of AS students in mind. The socialcoordination challenges characteristic of AS heightenthe need of this user group for some of the control mech-anisms, such as coordination policies and cooperativegestures, discussed earlier. Thus, we designed Sides toinclude system-enforced ownership of game pieces, anexample of the “private” whole-element coordinationpolicy. The DiamondTouch table’s user-identification fea-tures enforce turn-taking behaviors and prevent usersfrom interacting with arrow pieces that belong to othergroup members. These restrictions necessitate relianceon social interactions (such as offering suggestions orasking questions) to complete the game, rather thanallowing a student to bypass conversation with groupmembers by completing the entire puzzle independent-ly. Also, Sides includes buttons that must be pressed byall four players to achieve certain key game events, anexample of a cooperative gesture for achieving globalcoordination. These special voting buttons are locatedin front of each user’s seat and must be activated by allfour group members to test the current path for correct-ness or to quit the game. This feature encourages nego-tiation and coordination among the students, requiringthem to strategize and make requests of their teammates.

Three groups of students from a local special-needsschool played Sides under the guidance of their socialskills therapist. Initial reactions from students, the ther-apist, and the students’ parents have been encouraging.Our work on Sides provides a starting point for think-ing more broadly about user populations and comput-ing scenarios that can benefit from the social computingexperience that tabletop technology provides.

Discussion and conclusionThe projects described in this article represent an ini-

tial step toward considering social dynamics whendesigning software for multiuser shared-surface set-tings. We found that providing users with the ability todynamically change document accessibility on a table-top can facilitate shared document inspection and alter-ation, while also letting users guard their data againstintentional or inadvertent tendencies of users to inter-fere with other group members’ content on a sharedtabletop. Providing this type of built-in structure for anactivity (such as computer-enforced access control, turn-taking, and so on) can also make tabletop software moreaccessible to special-needs groups, such as adolescentswith AS. For all user groups, however, making items’current accessibility status visible is important for pre-venting confusion regarding accessibility.

In addition, cooperative gesturing is one means offacilitating active engagement of all group memberswith a tabletop application. Explicit awareness informa-tion that a tabletop system provides is another means tohelp users regulate their participation levels. This infor-mation can be subtle (for example, the use of audio feed-back attached to particular interactions can keep users



9 The Sides tabletop computer game requires a group of children to forma path enabling a frog to travel from the start lily pad to the end lily pad.Along the way, if this path intersects with insects, the group scores bonuspoints. The distribution of arrow pieces forces all four users to cooperate inorder to form a valid path. Buttons along each side of the table enableusers to vote on key game interactions (for example, testing the path orquitting).

aware of group members’ activity levels) or more explic-it (for example, individually targeted interaction visu-alizations can convince users to change their levels ofactivity). We also found that the location of key interac-tion items on a tabletop display impacts participationpatterns. Next-generation tabletop systems could mon-itor patterns of interaction and proactively move dataobjects near particular users’ seats to encourage themto become more involved in an activity.

By considering tabletop design holistically, includingboth the human–computer and human–human interac-tions that take place during tabletop activities, we hopeto ultimately create more usable and useful tabletopgroupware. ■

AcknowledgmentsWe thank Mitsubishi Electric Research Labs for donat-

ing a DiamondTouch table and for their contributionsto the coordination policies work. We also acknowledgeEileen O’Brien for her contributions to Sides.

References1. P. Dietz and D. Leigh, “DiamondTouch: A Multi-User Touch

Technology,” Proc. User Interface Software and Technology(UIST), ACM Press, 2001, pp. 219-226.

2. C. Shen et al., “DiamondSpin: An Extensible Toolkit forAround-the-Table Interaction,” Proc. Conf. Human Factorsin Computing Systems (CHI), ACM Press, 2004, pp. 167-174.

3. S. Greenberg and D. Marwood, “Real Time Groupware asa Distributed System: Concurrency Control and its Effecton the Interface,” Proc. Conf. Computer-Supported Cooper-ative Work (CSCW), ACM Press, 1994, pp. 207-217.

4. S. Izadi et al., “A Public Interactive Surface Supporting theCooperative Sharing and Exchange of Media,” Proc. UIST,ACM Press, 2003, pp. 159-168.

5. M.R. Morris et al., “Conflict Resolution in Paper and Digi-tal Worlds: Two Surveys of User Expectations,” CSCW Conf.Supplement, ACM Press, 2004.

6. M.R. Morris et al., “Beyond Social Protocols: Multi-UserCoordination Policies for Co-located Groupware,” Proc.CSCW, ACM Press, 2004, pp. 262-265.

7. M. Ringel et al., “Release, Relocate, Reorient, Resize: FluidInteraction Techniques for Document Sharing on Multi-User Interactive Tables,” Proc. CHI Extended Abstracts, ACMPress, 2004, pp. 1441-1444.

8. M.R. Morris et al., “Cooperative Gestures: Multi-User Ges-tural Interactions for Co-located Groupware,” Proc. CHI,ACM Press, 2006, pp. 1201-1210.

9. J. DiMicco, A. Pandolfo, and W. Bender, “InfluencingGroup Participation with a Shared Display,” Proc. CSCW,ACM Press, 2004, pp. 614-623.

10. S.D. Scott, M.S.T. Carpendale, and K. Inkpen, “Territorial-ity in Collaborative Tabletop Workspaces,” Proc. CSCW,ACM Press, 2004, pp. 294-303.

11. M.R. Morris et al., Supporting Cooperative Language Learn-ing: Interface Design for an Interactive Table, tech. report,Computer Science Dept., Stanford Univ., 2005.

12. A.M. Piper et al., “SIDES: A Cooperative Tabletop Comput-er Game for Social Skills Development,” Proc. CSCW, ACMPress, 2006, in press.

Meredith Ringel Morris is aresearcher in Microsoft Research’sAdaptive Systems and Interactiongroup. Her research interests includehuman–computer interaction, com-puter-supported cooperative work,and educational technologies. Mor-ris has a PhD in computer science

from Stanford University. Contact her at [email protected].

Anne Marie Piper is a userresearcher in Microsoft’s Entertain-ment and Devices Division. Herresearch interests include the designand evaluation of techniques to sup-port colocated cooperative technologyuse. Piper has an MA in learning,design, and technology from Stanford

University. Contact her at [email protected].

Anthony Cassanego is an under-graduate student in computer scienceat Stanford University. Cassanego’sresearch interests include computer-mediated interaction and interactionvisualizations. Contact him at [email protected].

Andreas Paepcke is a seniorresearch scientist and director of theDigital Library and BioACT Projectsat Stanford University. His researchinterests include interfaces for smalldevices, Web search, and browsingfacilities for difficult-to-index arti-facts. Paepcke has a BS and an MS

in applied mathematics from Harvard University and aPhD in computer science from the University of Karlsruhe,Germany. Contact him at [email protected].

Terry Winograd is a professor ofcomputer science at Stanford Univer-sity, where he codirects the Human–Computer Interaction Group and theteaching and research programs inHCI design. He is also a founding fac-ulty member of the Stanford Instituteof Design. Contact him at winograd@

cs.stanford.edu.

Anqi Huang is an undergraduate incomputer science at Harvard Univer-sity. His research interests includecooperative gestures and ways todesign graphical interfaces to deterphishing. He is a recipient of theArthur D. Little Innovations Fellow-ship. Contact him at huang3@fas.

harvard.edu.


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