Fikkert, F.W.

Hoeijmakers, Niek

van der Vet, P.E.

English

Input from the lower body in human-computer interfaces can be beneficial, enjoyable and even entertaining when users are expected to perform tasks simultaneously. Users can navigate a virtual (game) world or even an (empirical) dataset while having their hands free to issue commands. We compared the Wii Balance Board to a hand-held Wiimote for navigating a maze and found that users completed this task slower with the Balance Board. However, the Balance Board was considered more intuitive, easy to learn and ‘much fun’

University of Twente Research Information

Navigating a Maze with Balance Board and WiimoteWim Fikkert, Niek Hoeijmakers, Paul van der Vet, and Anton NijholtHuman Media Interaction, University of TwenteP.O. Box 217, 7500 AE, Enschede, The Netherlands{f.w.fikkert,n.j.hoeijmakers,p.e.vandervet,a.nijholt}@utwente.nlAbstract. Input from the lower body in human-computer interfaces can be ben-eficial, enjoyable and even entertaining when users are expected to perform taskssimultaneously. Users can navigate a virtual (game) world or even an (empirical)dataset while having their hands free to issue commands. We compared the WiiBalance Board to a hand-held Wiimote for navigating a maze and found that userscompleted this task slower with the Balance Board. However, the Balance Boardwas considered more intuitive, easy to learn and ‘much fun’.Keywords: H.5.2. User interfaces, Evaluation, Input devices and strategies.1 IntroductionNew forms of interaction keep flooding the market, introducing engaging and often un-expected new experiences to the public. Hand and other bodily movements now serveas input for game consoles. Similarly, input from the lower body in human-computerinterfaces can benefit the interaction by enabling natural proprioception. In addition,users have their hands free to perform other, simultaneous tasks such as issuing com-mands to a virtual game world (World of Warcraft, Killzone) that they are navigatingthrough with their lower body [1]. Such an interface has the potential to be more en-joyable because users can divide attention between tasks. In addition, lower body inputcan be highly entertaining, even enticing users to start interacting. This is, for exam-ple, illustrated by the Wii Fit game that is enthusiastically used in elderly homes forentertainment and in medical centers for rehabilitation1.Our contribution is an evaluation of the performance and, more importantly, enjoy-ability of users navigating a virtual maze world with their lower body while they areperforming cognitive tasks with a hand-held device [2]. Section 2 describes relatedwork on lower body HCI and ways to evaluate such interactions. In Sect. 3 we describeour evaluation of combining the Nintendo Wiimote and Balance Board for navigatingthrough a simple maze. Sections 4 and 5 present the results and conclusions of thisevaluation respectively.2 Related Work2.1 Lower Body InputNavigating virtual worlds through virtual walking, where the user can physically walkfreely through an entire world, has been addressed extensively in systems that fully1 In USA today, “Wii finds home in retirement communities, medical centers”, on 2008-05-14.A. Nijholt, D. Reidsma, and H. Hondorp (Eds.): INTETAIN 2009, LNICST 9, pp. 187–192, 2009.c© ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2009188 W. Fikkert et al.immerse their users. The VirtuSphere2 enables virtual walking by placing its users in-side a large sphere in which they can walk, run, roll and even jump. See Kruijf’s PhDthesis for a more extensive overview [3]. Interfaces that do not completely immersetheir users typically require them to remain stationary for large displays or use users’mobility in portable interfaces. The JoyFoot uses accelerometers to detect ankle move-ments for controlling navigation in a virtual world [4]. The JoyFoot was evaluated witha large display in a game setting where users had to navigate an asteroid debris fieldgame world in two dimensions by moving their feet on the floor. Reidsma et al. [5]presented their virtual dancer where users were enticed to engage in a dancing dialoguewith a virtual dancer. A game dance mat3 is used to detect the user’s presence while acrude computer vision solution is used to detect dancing motions. Map manipulationhas also been shown to benefit from combining a touch-sensitive wall-sized display forselection and activation with lower-body input from a Wii Balance Board for naviga-tion [1]. It has also been suggested that the Balance Board can be a useful modality toperform 1 DOF control tasks by the feet [6].2.2 Evaluating Input DevicesInput devices can be thoroughly evaluated on task completion times, error rates anduser satisfaction on various tasks using the ISO 9241-9 standard [7] which is based onFitts’ Law on human motor control. The standard defines performance measures forevaluating input devices or techniques using basic interfaces tasks such as tap, dragand trace. Like [1], we are interested to explore the effect of tracing complex paths, forexample, as found in map navigation. This goes beyond the underlying assumptions inFitts’ Law that eliminates the cognitive aspects of an interaction as much as possible inan effort to focus on the motor abilities of humans.3 MethodologyOur large display interface, see Fig. 1, combines lower-body input (from a Wii BalanceBoard) with input from the hands (from a Wiimote). Users performed a time-crucialnavigation task in a set of simple mazes during which they were required to input com-mands manually. These commands were issued at set locations in the maze, withoutwhich the user could not continue. The user controlled an avatar (green dot) in our mazetask. Subjects in this study were selected based on sufficient computer experience. Wehypothesize that the the Balance Board will be more intuitive for simultaneously navi-gating and issuing commands while not suffering loss in performance.3.1 Devices for Navigating the MazeThe Nintendo Wiimote and Nintendo Balance Board were used in a within-subjectsevaluation, see Fig. 1. The Wiimote has three perpendicular accelerometers and an IR2 Available online at http://www.virtusphere.com/, last checked feb. 2009.3 Dance Dance Revolution: http://www.konami.com/ddr/, last checked feb. 2009.Navigating a Maze with Balance Board and Wiimote 189Fig. 1. The maze navigation task combines the input from a Balance Board and Wiimote alike.Subjects enjoyed both navigation approaches; using either the Wiimote or Balance Board. Whilenavigating, users were required to press buttons on the Wiimote in order to complete the maze.camera that detects fixed light sources for absolute pointing. The Balance Board (orboard for short) has four pressure sensors at each of its corners.Our test subjects completed two scenarios in counterbalanced order. The first sce-nario (BW) combined the board with a single Wiimote. In BW, the board was used fornavigation; the subject stands on the board and shifts his center of gravity to move theavatar. Leaning forward moved the avatar up, left moved it left and so on. This is verysimilar to how a Segway works. The Wiimote could be held in the preferred hand (ei-ther left or right) and on set positions in the maze the subject was required to issue ancommand with it, see Sect. 3.2. In the second scenario (WM) our subjects only usedone Wiimote to control both the avatar and issue the commands in the maze. A similarform of navigating the maze with the Wiimote was selected compared to BW; the ac-celerometers were used to detect roll (for moving left and right) and pitch (for movingup and down). We specifically chose not to use the embedded IR camera for detectingpointing (see [2]) because it could bias the avatar’s movement speed. The avatar topmovement speed was equal for BW and WM, matching the maximum pitch or lean.3.2 The Maze TaskSubjects in our study navigated four mazes, seen from above, of varying difficulty, seeFig. 2. The four mazes were presented in the same order for both of the above scenarios.Before starting the first maze, our subjects were allowed a brief training session to getused to the device for navigation and to learn how to issue commands with the Wiimote.Each maze consisted out of a sequence of rooms that were connected by doors, endingwith a maze exit. The subject had to navigate/walk to a each (closed) door and, whilestanding in front of the door on a doormat, press a button to open the door. The buttonto press was displayed on-screen only when a subject was standing on a doormat. Aftera correct button-press, the door would open so that the subject could proceed to the nextroom. Pressing an incorrect button would give a visual error signal.190 W. Fikkert et al.(a) (b)Fig. 2. The set of mazes consisted out of very simple (a) linear paths to (b) more complex paths.Maze components were identified by their color. In all cases, only one path existed.3.3 User EvaluationA paired t-test was used to compare our two scenarios (BW and WM) to each other. Foreach maze we measured the task completion time in addition to the time that a user stoodstill on a doormat as measure for performance. As a measure for error rate, we countedimpacts with the walls of the maze and closed doors in addition to incorrectly enteredcommands. User personal data was gathered to assess their previous experience withthe devices in this experiment or similar input devices. After completing each scenario,the user filled out a questionnaire in which they rated the interaction. Upon completingboth scenarios the users rated which device they enjoyed the most for navigating.4 Results18 subjects participated in our evaluation, 4 female and 14 male (μ = 29 years, σ = 11years, ranging 18 to 56 years). 9 subjects held a Masters degree, 6 a Bachelors and 3had no degree. On a 1-5 scale, our subjects were proficient with the Wiimote (μ = 3.4,σ = 1.2) before taking part in the study but the Balance Board (μ = 2.3, σ = .9) andother motion capture solutions (μ = 2.0, σ = .8) were less familiar.With respect to performance, we found that task completion time with WM wassignificantly faster (17 seconds faster, p = 0.04). After the test, most subjects (10 forWM, 4 for BW) also indicated that they experienced WM to be the faster solution fornavigation. The number of wall and door hits did not differ significantly between BWand WM, nor did the number of incorrectly issued commands. However, 17 subjectsindicated after the test that they experienced WM to be less prone to bumping intowalls or doors (1 experienced no difference). We found that our subjects maintainedtheir location on doormats more consistently for WM (μ = 4.3 fewer drifts, p < 0.01).The total time spent on doormats did not differ significantly but on average each passtook significantly less time using BW (μ = 0.47 seconds, p = 0.04).We found no significant difference in ease of learning, the intuitiveness of the nav-igation and smoothness of the navigation between both techniques (BW and WM) forNavigating a Maze with Balance Board and Wiimote 191navigation in our user opinions after each scenario. However, in the evaluation after thetest most subjects (10) indicated that BW was easiest to learn while 6 subjects foundWM easier to learn. Likewise, BW was considered the most intuitive (13 subjects, 2for WM). Our subjects rated the navigation accuracy significantly higher in favor ofWM (p < 0.01) after each scenario and in the evaluation after the test (12 subjects, 2for BW). Although we did not find a significant difference for opening the doors be-tween BW and WM, five subjects indicated that they were not familiar enough with theWiimote to find the required button right away. Although there was no significant dif-ference in the extent that our subjects enjoyed using either WM or BW, they indicatedafter the test that BW was the most fun (12 while 2 had more fun with WM).In observations during our trials we noticed that most subjects navigated in onlyone direction with WM at any one time. For example, a subject would move up firstand then turn left rather than moving in both directions simultaneously. Similarly, weobserved that our subjects would in most cases complete the navigation task first. Onlyafter ensuring that they remained stationary on a doormat would they focus on openingthe door. During the trials four subjects commented that they found our implementationfor moving up and down with WM counter intuitive. They would rather invert it so thatpitch down moves the avatar forward, arguing that that would be exactly the same asthe BW implementation.5 Conclusions and Future WorkBy using the lower body to navigate a virtual world users keep their hands free to com-plete to perform other tasks simultaneously such as issuing commands. We have com-pared the Wii Balance Board to a hand-held Wiimote for navigating a series of simplemazes. While navigating the maze of consecutive rooms, our users had to open doorsbetween these rooms on set locations directly in front of the doors. Users could navigatewith the board by shifting their center of gravity through leaning or by changing the rolland pitch of the Wiimote in their preferred hand.We hypothesized that the Balance Board would be more intuitive for the navigationtask while not suffering a performance loss. Although we found that the board waseasier to learn and use, the Wiimote was significantly faster in navigating the mazewithout resulting in an increase in navigation errors or errors in the issued commands.This suggests that using the same input modality (a hand-held device) performs betterfor navigating a virtual world while simultaneously issuing commands. However, weargue that the fun-factor of an interface is equally or even more important for manyapplications, especially games. Our subjects strongly indicated that they enjoyed usingthe combination of Wiimote and the Balance Board more, although it was not faster tocomplete the game. This raises a good point in that novelty is a very important factor forperceived the fun-factor. We expect that a comparison between Wiimote and joystickwould provide similar differences. An unbiased assessment would require the users tobecome much more proficient with both devices.Some subjects wanted to invert the pitch for navigating to match Balance Boardnavigation; leaning forward would move the avatar forward. We chose not to implementthat approach in favor of mimicking ray-casting to the screen where pointing to thebottom of the screen would move the avatar down.192 W. Fikkert et al.One aspect that we did not investigate was to what extent the lower body is suitedto perform navigation as well as issuing the crude commands that we used in our eval-uation. When compared with the current results we expect to find an increase in taskcompletion time with a similar error rate. Trajectory analysis can be used to evaluate thedistance to the ideal path through the maze. In addition, our observation that subjectsmoved the avatar along one axis at any one time could be grounded.Acknowledgements. This work is part of the BioRange program carried out by theNetherlands Bioinformatics Centre, which is supported by a BSIK grant through theNetherlands Genomics Initiative, and the GATE project, funded by the NetherlandsOrganization for Scientific Research (NWO) and the Netherlands ICT Research andInnovation Authority (ICT Regie).References1. Schöning, J., Krüger, A.: Multi-modal navigation through spatial information. In: Cova, T.J.,Miller, H.J., Beard, K., Frank, A.U., Goodchild, M.F. (eds.) GIScience 2008. LNCS, vol. 5266,pp. 151–154. Springer, Heidelberg (2008)2. Fikkert, W., van der Vet, P., Nijholt, A.: Hand-held device evaluation in gesture interfaces. In:Gesture Workshop 2009 (February 2009)3. Kruijff, E.: Unconventional 3D User Interfaces for Virtual Environments. PhD thesis, Institutefor Computer Graphics and Vision, Graz University of Technology, Graz, Austria (October2006)4. Barrera, S., Takahashi, H., Nakajima, M.: Joyfoot’s cyber system: a virtual landscape walkinginterface device for virtual reality applications. In: International Conference on Cyberworlds,pp. 286–292 (2004)5. Reidsma, D., van Welbergen, H., Poppe, R., Bos, P., Nijholt, A.: Towards bi-directional danc-ing interaction. In: Harper, R., Rauterberg, M., Combetto, M. (eds.) ICEC 2006. LNCS,vol. 4161, pp. 1–12. Springer, Heidelberg (2006)6. de Haan, G., Griffith, E., Post, F.: Using the Wii Balance BoardTMas a low-cost VR interactiondevice. In: VRST 2008: Proceedings of the 2008 ACM symposium on Virtual reality softwareand technology, pp. 289–290. ACM, New York (2008)7. ISO: Ergonomic requirements for office work with visual display terminals (vdts) - part 9:Requirements for non-keyboard input devices. Technical Report ISO/DIS 9241-9:2000, Inter-national Organization for Standardization (2000)

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