Serious Interface Design for Dental Health: WiiMote-based Tangible Interaction for School Children Kathrin Gerling, Matthias Klauser and Maic Masuch Entertainment Computing Group University of Duisburg-Essen Forsthausweg 2 47057 Duisburg, Germany {kathrin.gerling, matthias.klauser, maic.masuch}@uni-due.de ABSTRACT Moreover, possible positive effects of tangible interfaces This paper describes a camera-based approach towards for education are discussed, e.g. the improvement of creating a tangible interface for serious games. We learning processes due to the closer link between cognition introduce our game for dental health targeted at school and perception as well as the improvement of collaborative children which implements the Nintendo WiiMote as work between children sharing the same computer [13]. infrared camera. Paired with a gesture-recognition system, Besides, studies have shown that the availability of tangible this combination allows us to apply real-world items as interfaces for children may reduce the need for instruction [23]. input devices. Thereby, the game tries to address different aspects of dental hygiene along with the improvement of In this paper, we describe our tangible approach towards children’s motor skills. In our focus group test, we found interface design for a game for dental health which features that tangible interfaces offer great potential for educational a user interface based on real-world items and thereby tries purposes and can be used to engage kids in a playful to convey psychomotor skills along with factual knowledge learning process by addressing their childlike curiosity and on dental hygiene. fostering implicit learning. RELATED WORK The issue of dental hygiene of children and teenagers has Keywords rarely been addressed by serious games. Serious Games, Tangible User Interfaces, Design for Children A ubiquitous approach towards teaching tooth brushing to school children has been suggested by Chang et al. [3]. INTRODUCTION Their system tracks children’s brushing behavior while Research has shown that insufficient dental hygiene of cleaning their teeth and presents brushing results on an children and teenagers has a negative impact on the LCD display. Additionally, they conducted an development of their second dentition: Children whose accompanying study which showed an improvement of primary teeth have been affected by cavity are at a brushing strategies and a significantly longer overall significantly higher risk of developing caries during brushing time. Nevertheless, the application only includes adolescence and adult life [12]. Therefore, it is important to few game elements and focuses on sensorimotor skills inform children and teenagers about different means of instead of game play, which might affect player’s dental hygiene at a very early stage. Because it is difficult motivation in the long run. to reach school children and teenagers through educational videos, flyers or other information sessions, new ways of Dental Attack [4] is a serious game featuring 3D graphics communication have to be found. We believe that a serious in which the player has to protect a large tooth from cavity game has the potential of reaching our target audience due by administering correct cleaning behaviour. It aims at the positive impact of playful applications on children’s improving the player’s knowledge and motivation motivation [15]. In addition to that, tangible user interfaces regarding dental hygiene, but possible positive effects of enhance immersive effects of digital games, and thus have the game have not been validated in the context of an the potential to deeply engage users in game play [6]. evaluation. Additionally, a wide range of flash games featuring the topic of dental hygiene is available on the internet. Furthermore, tangible interfaces for children have frequently been discussed and a variety of playful applications has been designed. TICLE was designed by Scarlatos et al. and is an early approach to game design based on tangible interfaces for children. It is a tabletop tangram game which supervises player’s movements and offers help when necessary [19]. Karime et al. [9] created a Magic Stick which enables very contamination and plaque to dental decay, the player may young children to use digital entertainment systems. The unlock bonus items such as fluoride gel or chewing gum by tangible stick combines RFID and Bluetooth technology entering quick mini game challenges or decide to switch to and can be used to read information about pictures from cleaning-mode in order to administer cleaning treatment. tagged image books which are then displayed in a virtual After switching to cleaning-mode, the player is asked to scene. choose from a set of three cleaning instruments displayed at Ryokai et al. [17] developed the concept of I/O Brush, a the top of the screen (cf. Figure 2). He may decide to use a camera-based drawing tool which allows children to read tooth brush, mouthwash or dental floss to remove traces of color and texture information from their environment and comestibles and plaque. Depending on the player’s choice, apply it to virtual images. an adequate input device allowing the conduction of Furthermore, Ho et al. [8] approached serious game design different cleaning gestures has to be selected (cf. Enhanced from the perspective of tangible user interfaces and created Tangible Interaction). a health game aimed at children attending primary school During game play, the user is given the possibility of which implements the Nintendo WiiMote. returning to each of the game modes as necessary. At the end of each level, scores are calculated based on the GAME CONCEPT average status of the group of teeth and the overall quality The game concept presented within this paper is based on of cleaning behavior administered by the player. Thereby, the idea of fusing game mechanics and learning units in the player receives additional feedback regarding his in- order to create an immersive user experience. It features a game performance. combination of two complementary game modes which incorporate different didactic goals. Furthermore, the concept aims at the implementation of intuitional interaction paradigms designed to engage the player in game play and to facilitate learning processes. A detailed description of the game concept and its didactic foundation was published in [7]. Game Design Our game design suggests the combination of two game modes, nutrition-mode and cleaning-mode, to implement in-game challenges which address different learning objectives. Figure 2: Brushing input in cleaning-mode. Didactic Goals As a result of the combination of nutrition-mode and cleaning-mode, the game addresses three basic didactic goals, which can be mapped to Bloom’s Taxonomy of Learning Domains [1]: • motivation (Affective Domain) • factual knowledge (Cognitive Domain) • sensorimotor skills (Psychomotor Domain) The game tries to raise children’s motivation by putting Figure 1: Overview of nutrition-mode. them in charge of a group of teeth while equipping them with different tools. During game play, children are In nutrition-mode, the player has to take care of a group of continuously asked to make choices and consider teeth advancing through the game in a style similar to 2D consequences of their actions while being provided with side-scrolling games (cf. Figure 1). Each level consists of a immediate feedback. Thereby, the game aims at the set of comestibles which the teeth have to chew. improvement of their self-efficacy while challenging their Additionally, a time limit which represents an average factual knowledge regarding dental hygiene. Furthermore, playing value is implemented to support the calculation of a our game concept addresses motivational aspects by the comprehensible high score at the end of the level. While presentation of teeth as vulnerable creatures which depend the group encounters challenges represented by a variety of on the player’s care and protection. comestibles causing negative effects ranging from Additionally, the transfer of factual knowledge is fostered children. Therefore, an enhanced tangible interaction by the visualisation of dental decay caused by the applying real-world items as input devices was consumption of comestibles during nutrition-mode. implemented. Depending on the type of comestible which was Enhanced Tangible Interaction encountered by the group of teeth supervised by the player, In contrast to our suggestion for a basic interaction scheme, plaque or contamination is caused. Furthermore, the speed the enhanced design embeds real world items into the of decay is affected by the core ingredients of each game. It introduces infrared input recognition which is comestible, such as sugar (e.g. chocolate) or acid (e.g. based on the idea of implementing a gesture-based interface cola). Besides, the game accentuates dependencies between which allows young children to actively participate in game eating habits and their impact on specific requirements of play and engages older kids due to its innovative nature. adequate means of cleaning through different game mechanics. In this context, we decided to use Nintendo’s WiiMote as primary input device because it is one of the most popular The development of sensorimotor skills is addressed by the controllers for digital games. Furthermore, it provides us implementation of cleaning-mode, which requires gesture- with a variety of information on user input through its based interaction and includes the application of real-world button interface, translatory sensors and the additional items as input devices (cf. Enhanced Tangible Interaction). infrared interface. Additionally, the availability of a wide INTERACTION DESIGN range of third party software such as the WiimoteLib [22] Interaction design for children and teenagers is a facilitates the implementation of the device. challenging task due to the particularly wide range of The game requires a total of two WiiMotes: One Mote is cognitive and sensorimotor skills of the target audience. used as regular pointing device, another mote is located in This requires an inclusive design approach which takes front of the player and serves as infrared camera. In the different stages of children’s development into account [2]. following section, both input paradigms will be described. Our game tries to address this issue by offering two interaction concepts which require different levels of sensorimotor precision and both try to reduce children’s cognitive load by implementing facile input paradigms. The basic approach towards interaction design includes mouse and keyboard input, whereas the enhanced interaction concept is based on the implementation of tangible controllers, i.e. the Nintendo WiiMote and real-world items. Additionally, we believe that our tangible approach to interface design may address a broader audience and activate children’s curiosity, which would be ideal regarding our target audience of both younger children and teenagers. Basic Interaction Design The game features a conventional user interface based on Figure 3: Overview of the complete setup required for the combination of mouse and keyboard input. The player item-based input. is offered the possibility of interacting through point-and- click operations as well as keyboard input: During WiiMote Input nutrition-mode, the group of teeth is moved using arrow The primary WiiMote controller is implemented as keys. After switching to cleaning-mode by using the mouse pointing device. This setup requires a wireless infrared to click on a particular tooth, further mouse input is sensor bar similar to the bar delivered with the Nintendo required to perform different cleaning actions. In order to Wii, which is positioned in front of the player in order to evaluate the quality of the player’s attempts to use different track input via the infrared interface. Furthermore, button cleaning instruments, we implemented a gesture input is registered to trigger in-game events. recognition system which is also used within the enhanced During nutrition-mode, this remote is used to control the tangible interaction and is described in the following group of teeth representing the player, to participate in section. mini-games in order to unlock bonus items and to switch to The advantage of this basic approach is the wide cleaning-mode when necessary. In cleaning-mode, the availability of mouse and keyboard as input devices. pointing mote may be used to select an appropriate Additionally, many children and teenagers have previous cleaning device. Once a device has been selected, the experience with similar interaction paradigms, which is player needs to exchange the pointing remote with the likely to provide an easy entry to game play. However, corresponding reflector-based input device. input in cleaning-mode requires accurate mouse movements which might not be suitable for younger Camera-based Input infrared light towards the player in combination with the Instead of using the WiiMote as pointing device in camera WiiMote allows us to track user input without combination with a stationary sensor bar, it is also possible attaching any electronics to the input devices of our choice. to implement the remote as fixed infrared camera and move Because we wanted to be able to track more than one input a source of infrared light instead. Thereby, it is possible to event at a time at a later point of development, we decided track different input gestures conducted by the user if he or to adapt a multi-touch finger tracking system originally she is equipped with adequate input devices. This allows us designed by Chung Lee [11] which supports up to four to implement a tangible user interface which is based on the touches and requires an LED array throwing infrared light idea of utilizing real world items as input devices. at the player. It is written in C# and can easily be combined with the latest version of Microsoft’s XNA Game Studio System [14] and the WiimoteLib [22]. User To improve tracking results, Chung Lee suggests that Game players attach reflective tape to their finger tips which WiiMote Input Detection increases the amount of infrared light being thrown back at Input Input the camera remote. Instead of adding reflective tape to the Evaluation Input Items Gesture player’s fingers, we decided to attach it to a tooth brush, a User cup and an imitation of dental floss. In order to achieve an Recognition Brush Feedback System acceptable transmission result, we used Scotchlite Solas GradeTM, which is a type of reflective tape that is Cup commonly used in shipping. Besides a high flexibility, the Display / tape concentrates light rather than having a dispersive Floss Audio effect which increases the amount of light being returned to the camera remote. Figure 4: Overview of the interaction between user and Interface and User system.. Recognition System IR light Tools with Technically, there are two different approaches based on LED Array reflective tape the idea of casting infrared light on a stationary infrared (Tooth brush, cup or dental floss) camera which we considered for our setup. Both require the reflection implementation of additional LEDs similar to those used Camera WiiMote for the original sensor bar. The LEDs utilized for the array should ideally have a peak wavelength of 950nm, otherwise tracking results are not stable enough and are easily Gesture recognition Game influenced by other sources of infrared light, e.g. sunlight. At first, we tried to invert the regular pointing system by Figure 5: Interface setup and information processing. attaching LEDs directly to the objects which would then be used as input devices. This requires a power supply which either needs to be attached to the object or has to be In order to receive a strong infrared signal, we used an LED connected by wire. Unfortunately, this may be a array consisting of 40 LEDs with a wavelength of 940nm disadvantage when designing for children since the (+/- 50nm). We installed the LED array on a wooden rack prototypical input devices we developed were very fragile with a little hinge which allows for the adjustment of the and could easily be damaged when dropped or carelessly LED array in a very flexible manner. This is particularly handed over to another person. Because we were intending important because the angle of the array needs to be to use the interface for teenagers and younger children, it adjusted according to each player’s body size to grant an was also problematic that most LEDs which are currently optimal tracking result. On top of the rack, a clamp was available have an operating temperature up to 75°C and installed which allows us to mount the camera WiiMote therefore cannot be used in interface design for kids accordingly (cf. Figure 3). without the risk of injury. However, this method returns good transmission results and offers the possibility of The advantage of this method is the fact that the input tracking single input devices as LEDs may be used as devices are lightweight and fully functional without any markers which are recognized by the system during game additional electronics or other attachments which might play. Thereby, it is possible to determine whether the disturb the user (e.g. wires connecting the device to the player is using the correct input device. system). If necessary, all input devices can be replaced at low cost, because average retail items can be used which Alternatively, it is possible to implement a system which only need to be enhanced with reflective tape. does not require the attachment of LEDs to the hardware Figure 5 shows how input information is processed by the user interface: The installation of an LED array casting system described in the previous section. First, the LED array casts infrared light towards the objects utilized by the player. Second, light is reflected by the input device and thus recorded by the camera WiiMote. Then, 2D coordinates representing the relative position of the input device to the camera are obtained and translated into mouse coordinates. Therefore, it is possible to apply regular mouse gesture recognition algorithms during the next step of information processing. Afterwards, information regarding the quality of player input is passed on to the game and corresponding feedback is displayed to the player. Figure 7: Gesture recognition for tooth brush input. For each instrument in cleaning mode, a corresponding If the tooth brush is used correctly, a circular movement is object was chosen and laminated with reflective tape. Thus, registered by the system. As this is a continuous process, the game features a tooth brush, a cup as well as an the cleaning period is split into cycles. Once one cycle imitation of dental floss made of cord and wooden pearls within the brushing process is finished, the recognition (cf. Figure 6). system evaluates the accuracy of the player’s cleaning The following section describes the set of characteristic movement by comparing player input to an ideal circular input gestures which is required to play the game. movement. Figure 6 shows the recognition process: If user input is registered which may be similar to circle A (good) To use the cup filled with mouth wash, the player has to lift or circle C (bad), it is compared to the ideal circle B. Based it up to his face and pretend to drink out of it. Thereby, the on four distinctive points of the player’s input gesture, the camera records a vertical movement which can easily be area of the circle is approximated and compared to the ideal identified by the gesture recognition system. Dental floss is circle which is based on a set of four predefined values. It used by picking up the cord with both hands and slowly was necessary to reduce the amount of values drastically to lifting both ends in an alternating rhythm. Since the reach an acceptable level of system performance and to be tracking system supports multiple input sources, two able to deliver immediate visual feedback to the user. In vertically moving objects are detected and submitted to the order to determine whether the input cycle has been game as player input. finished, each circle is split into four areas (cf. Figure 7). The transition between two areas can be detected by a corresponding change of the X and Y values of mouse coordinates. Depending on the alteration of these coordinates, the system defines an initial starting point at which the cycle started and is later expected to end. Thereby, the system is able to distinguish between circular strokes and mere vertical or horizontal scrubbing. Finally, the user is provided with visual feedback regarding the individual cleaning performance. In contrast to regular mouse and keyboard input, the enhanced interaction design offers a more complex, yet intuitional tangible interface which we expect to have a positive impact on player’s motivation and engagement. In the following chapter, we describe the results of a first focus group test during which both interaction paradigms were compared. Figure 6: Tools with reflective tape. If the player uses the cup or dental floss, the game only FOCUS GROUP TESTING checks whether the corresponding gesture has been In order to evaluate the two interaction concepts presented completed. However, if the tooth brush is used, the quality within the previous chapter, a stable and fully playable of the gesture has to be evaluated. Therefore, a more prototype which offers both mouse and keyboard input as complex interpretation process is required which is able to well as WiiMote and item-based interaction was created. determine the precision of each player’s cleaning behavior. The focus-group test was conducted with nine school Thus, we implemented a simple algorithm which allows us children with a mean age of 10 (range 9 to 11). The group to judge whether player input was good, average or bad. consisted of three girls and six boys, all of the children were from socially disadvantaged families and therefore at a generally higher risk of suffering from the consequences of insufficient dental hygiene. Therefore, the focus group represented one of the core audiences of our design concept. Besides, all participants had previous experience using the computer and playing games. Setting and Method In general, the focus-group test showed that new At the beginning of the test, the children were divided into technologies offer great opportunities for educational two groups. Group A consisted of five children and was games because they have the potential to engage children in later on presented with the enhanced tangible interaction a playful learning process. Teaching staff positively using both WiiMote and real-world items. Group B highlighted the fact that their students actively discussed in- consisted of four children who were asked to play the game game actions as well as aspects of dental hygiene, which in using keyboard and mouse. Each group was granted one their opinion offers a good opportunity of picking up the hour of playing time followed by a fifteen-minute topic of dental hygiene in a more formal context. Thus, the structured group interview. Before the start of the playing game could probably be used in a classroom context to session, the interaction methods as well as keyboard and introduce the topic of dental hygiene. Furthermore, the button mappings were explained. During game play, implementation of tangible interfaces in combination with children were observed and asked questions about their in- gaming applications may foster implicit learning processes, game actions according to the Active Intervention method because the player’s desire to master the game requires suggested for the evaluation of interactive products with mastery of the input devices, too. children subjects [21], which is closely related to think- DISCUSSION aloud techniques [2, 5]. The test was conducted within the The focus group test showed that the tangible approach group’s school environment and accompanied by teaching towards interaction design for serious games has the staff. potential of engaging children in game play and learning Results and Interpretation processes. Nevertheless, this first approach only included Children’s comments during the playing session showed few subjects and should be understood as an indication of that group B generally had no difficulties approaching the future research focuses rather than an extensive evaluation game, because all children had previous experience using allowing definite conclusions regarding usability, interface the combination of mouse and keyboard as input devices design and learning success. for digital games. On the contrary, participants of group A needed assistance when switching from WiiMote to item- One of the biggest advantages of the reflector-based based interaction. Difficulties were primarily caused by the approach to interface design presented within this paper is fact that the specific version of the LED array required the fact that all tangible input devices required during careful player alignment and did not take children’s cleaning-mode are lightweight and robust as they do not restlessness into account. In that context, using a regular utilize fragile technology. Additionally, they can easily be tooth brush and cup was advantageous because these items replaced at low cost since the current implementation is turned out to be very robust and are barely affected by based on conventional cleaning instruments enhanced with careless treatment. Additionally, comments showed that reflective tape, which is ideal for the design of tangible children within group A were enthusiastic about the use of interfaces for children. real-world items as input devices and were highly However, the current implementation does not allow the motivated to enter cleaning-mode to take proper care of game to determine whether the player utilized the correct their virtual teeth. In this regard, we observed that children cleaning instrument. This may be problematic if the game within group A generally showed a higher willingness to is played without supervision. Besides, we learned about a cooperate with their peers than participants within group B. number of usability issues regarding the setup process of the game during the focus group test, for instance We believe that the increase in participants’ establishing a Bluetooth connection between the WiiMote communication can be accredited to the availability of and a PC is rather difficult due to connectivity issues and several input devices which encourages collaborative game requires a level of technical expertise which should not be play rather than indicating a 1:1 relationship between one assumed. Furthermore, the current setup of the WiiMote user and the system through a regular mouse and keyboard and LED array is very prototypical (cf. Figure 3) and is not setup. suitable for unsupervised use by children and teenagers yet. The observations which were made during both playing sessions were generally supported by children’s statements FUTURE WORK and comments in the context of the follow-up interview. Future work will include the replacement of the camera All of the subjects within group A claimed that they WiiMote by a regular infrared camera to address preferred cleaning-mode over nutrition-mode because it connectivity issues and to facilitate the setup process which allowed for the use of real-world items as input devices, is required to play the game. This is especially important as which they commented on as “fun”, “magic” and a comprehensive clinical study requires an increased level “exciting”. Participants of group B reported that they of usability regarding the technical installation as the enjoyed playing the game but did not make any distinction system needs to be set up by both teaching and medical between both modes. When questioned about the user staff. Additionally, we are planning on introducing a new interface in particular, they explained that they found the rack to carry the camera WiiMote and the LED array which interface to be usable, but their comments did not show the is suitable for repeated use in the context of a clinical study. same curiosity and enthusiasm as those of participants Besides, it is planned to add a basic logging system to the within group A. game which tracks the most important in-game actions performed by the player, such as the use of cleaning Conference on Design & Children (IDC ’07): instruments or the frequency of cleaning sequences during Methodology, 9-16. game play. Additionally, metadata such as the overall 6. Falk, J. & Davenport, G. (2004): Live Role-Playing playing time and high scores could be included in the Games: Implications for Ubiquitous Computer Game logfiles. Implementing a logging system offers the Interfaces. In: Proceedings of ICEC 2004. opportunity of supporting possible general findings of the International Conference on Entertainment Computing, evaluation by individual player data, which may support Eindhoven, 127-138. the interpretation process of evaluation results. 7. Gerling, K. & Masuch, M (2009). Serious Game Additionally, our hypothesis regarding the activation of Design using the Nintendo WiiMote: Motivating implicit learning processes through tangible user interfaces School Children to Improve Dental Hygiene. In: for serious games needs to be tested within an evaluation of Proceedings of ITECH 2009, Nottingham. learning success. This includes the revision of additional hypotheses concerning the transfer of factual knowledge as 8. Ho, J.H., Zhou, S.Z.Y., Wei, D. & Low, A. (2009). well as psychomotor aspects. We hope to conduct these Investigating the Effects of Educational Game with Wii tests in the context of a clinical study which is currently Remote on Outcomes of Learning. In: Lecture Notes in being prepared. Computer Science: Transactions on Edutainment III. Berlin und Heidelberg: Springer. Furthermore, we would like to conduct further research regarding the aspect of the development of game mechanics 9. Karime, A., Hossain, M.A., Gueaieb, W. & Saddik, in combination with didactic goals. The fusion of game A.E (2009). Magic Stick: A Tangible Interface for the elements and learning units to positively influence Edutainment of Young Children. Proceedings of the children’s self-perception and thereby affect behavioral 2009 IEEE international conference on Multimedia outcomes has previously been proven to be effective in the and Expo, 1338-1341. context of a serious game designed for children diagnosed 10. Kato, P.M., Cole, S.W., Bradlyn & A.S., Pollock, B.H. with cancer [10], but has rarely been discussed from the (2008). 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