Antonia Kampa
email: antonia.kampa@hs-rm.de

Kathrin Stöbener
email: kathrin.stoebener@hs-rm.de

Ulrike Spierling
email: ulrike.spierling@hs-rm.de

User Interface Prototyping for Handheld Mobile Augmented Reality Applications

Keywords: Augmented Reality, User Interface Design, Prototyping

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction: AR User Interface Design Prototyping Tool

Interaction with Augmented Reality (AR) and the need for appropriate user interfaces have been topics of research for several decades [START_REF] Bai | Analytic Review of Usability Evaluation in ISMAR[END_REF][START_REF] Billinghurst | Designing Augmented Reality Interfaces[END_REF][START_REF] Macintyre | DART: a toolkit for rapid design exploration of augmented reality experiences[END_REF]. However, available design frameworks mainly target expert developers and -users such as programmers. There are no standard or commonplace user interaction metaphors, as it has widely been a niche topic. For a long time, AR has also been associated with special devices such as headmounted displays and extra hardware for tracking or tangible interfaces [START_REF] Billinghurst | Designing Augmented Reality Interfaces[END_REF]. Only recently, new kinds of mobile apps for off-the-shelf phones and tablets become widespread. They include AR in form of a visual overlay of digital information on real objects or landmarks on a camera image. For entertainment and education purposes, such AR applications are to be conceived in a consumer market. This development produces an increasing need for non-programmers, such as media designers, to tackle AR elements as new media to be included in the conception and design of communication with their target groups. Like in other areas of media conception, interface design and graphics, designers need easy to use prototyping tools.

In the research project SPIRIT, a location-based mobile AR application has been developed that includes AR video overlay on specific spots of a cultural heritage site. Visitors shall experience entertaining on-the-spot storytelling, together with scavengerhunt-like spatial interactions and information seeking, based on mobile device sensors. Storytellers and UI designers have been involved in the design of UI features integrated with the interactive story's concept. Figure 1 shows an early functional prototype, that had to be redesigned for more user guidance. This interdisciplinary development afforded several stages of prototyping before the system's full implementation [START_REF] Alce | Prototyping Methods for Augmented Reality Interaction[END_REF]. Easy prototyping of location-based AR experiences requires tools that go beyond existing approaches. As a side result in the SPIRIT research project, we developed the AR UI prototyping tool MockAR for the project's non-programming designers. It supports the widely known principle of 'wire framing', used to draft and test so-called click dummies in early development stages [START_REF] Snyder | Paper Prototyping: The Fast and Easy Way to Design and Refine User Interfaces[END_REF]. MockAR plays back image sequences that can be experienced based on a wide range of user interactions using handheld devices' sensors.

SPIRIT: Outdoor Cultural Heritage AR Video Entertainment

The SPIRIT AR application delivers location-based stories, targeted at outdoor and indoor cultural heritage education on site. The goal is to achieve a feeling of 'presence' on the spot supported by interaction with the application, so that visitors can engage with their historical surroundings. The AR overlay consists of pre-produced video snippets representing 'spirits of the past' at the location of their former living (compare Figure 1). Technically, the developed AR system relies on GPS and image recognition to trigger content, using no dedicated markers, but reference images found in the physical environment. This technological vision of a natural seamless interaction is at the same time a challenge for designing the right affordances for users, as there are no technically given 'calls to action' for finding the right spots. While there are no standards, UI designers need to be included in the design process, to come up with innovative ideas. Therefore, an interdisciplinary user interaction design process is needed.

Augmented Reality User Interaction in SPIRIT

While several common AR interaction styles are not necessary, such as manipulating 3D objects, there are other challenges for users to be addressed in a user interface, like orientation in the environment and interacting with spirit videos.

In the SPIRIT scenario, the main AR user interaction consists of pointing the camera towards interesting surroundings, anticipating that (markerless) image recognition leads to a trigger for content. Users need to steady their mobile device until the recognition algorithm has successfully captured 'reality', which can then be overlaid with information, videos or other media assets. In practice, a user searches the whole area for suitable visual backdrops that could serve as image triggers, with the help of a UI that supports the right anticipation. On success, ghost-like characters as semi-transparent video deliver story content in form of dialogues, while users keep the camera focus on the triggered backdrop also accessing limited dialogue functions. In summary and besides this basic interaction loop, user actions include:  walking between specific outdoor locations relevant for the told story,  searching visual backdrops as image triggers (finding interesting story locations)  tapping on buttons in a conventional GUI-like interface  tilting the mobile device up and down, changing between augmented story and a general GUI Further, we develop and evaluate novel input styles using different sensors, such as turning around like in a panoramic image, turning at specific angles up to 360 degree, or pitching and shaking the mobile device. We also test setting a timer for automatic displays without a trigger image, for example as several step-by-step hints and instructions, helping the user to find the right locations and backdrops.

User Interface Design Prototyping Versus User Interface Development

For the above-mentioned interactions, the mobile application needs to be equipped with various UI elements offering meta-information and hints for the user. As there is not a straight-forward standard solution, several optional creative design ideas are developed.

In a cycle of design and formative evaluation, these alternatives need to be tested long before final implementation. In traditional interactive media (such as for desktop, web and touch applications using point-and-click or tap interaction), so-called wireframes are created with basic tools [START_REF] Snyder | Paper Prototyping: The Fast and Easy Way to Design and Refine User Interfaces[END_REF] as simple as for example MS-PowerPoint. The result can be experienced clicking linearly through ideal progressions of use, mostly at the desktop. This approach has been used at first, however it is limited for experiencing location-based AR issues. These include the difference between lighting and readability conditions indoors vs. outdoors (see Figure 2), the handling of the device including holding its weight and reach space for touch interaction, as well as issues concerning the specificity of the outdoor location, far away from office space. To fill this gap, we developed MockAR, an application to be used for low-fidelity prototyping of UI design alternatives.

User Interface Wire Framing for AR Technology

An increasing number of wireframing tools for non-programmers exist, suggesting that creative design and programming tasks are distributed to different persons in a team [START_REF]Aurasma Development Kit[END_REF][START_REF] Balsamiq | Rapid, effective and fun wire framing software[END_REF][START_REF] Layar | Augmented Reality[END_REF]. However, these lack the possibility to test the above-mentioned issues of mobile AR, while dedicated AR tools are programming libraries [START_REF] Macintyre | DART: a toolkit for rapid design exploration of augmented reality experiences[END_REF][START_REF] Vuforia | Vuforia Play Mode for Unity[END_REF]. The WozARd [START_REF] Alce | Prototyping Methods for Augmented Reality Interaction[END_REF] prototyping tool for non-programmers provides AR, however, it is limited by its Wizard of Oz concept relying on a supervisor. In short, we did not find suitable tools enabling non-programmers to quickly test and evaluate AR user interaction ideas, which motivated the development of MockAR.

MockAR Details

MockAR engages non-programmers in the UI design process of AR interactions, making this task accessible to a wider group of creators used to wireframing. MockAR emulates AR effects by displaying a linear order of semi-transparent images in front of camera-captured video. It makes full use of available sensors of mobile devices as input options to advance the image sequence. The image succession is determined by alphabetical order of image file names (0-9, A-Z). Transition between two images is set by an interaction keyword (e.g. shake, pitch, turnL, turnR, tap) contained in the last six letters of the file name. In SPIRIT, we used MockAR with interactions like tapping on screen (default), shaking, pitching by 90 degrees, turning the device left and right (Figure 3), and setting a timer. A six digit number sets timed image transitions in milliseconds. Technical skills needed for using MockAR are image editing, changing filenames, saving files on an Android device and installing and starting the Android app on a mobile device. Therefore we assume MockAR is easy to use for non-programming user interaction designers.

Proof of Concept

Figure 5 shows an example of how MockAR has been successfully used to evaluate creative ideas. Designers came up with the idea to conceive the app generally as metaphorical 'magic equipment', asking a user to apply 'energy' in order to visualize a spirit. The questions then was how 'applying energy' can be performed. One idea was to let the user shake the tablet (Figure 5, upper row from left to right). Alternative ideas included using two thumbs to swipe at the same time, or, just standing still and waiting while pointing at a backdrop (Figure 5, lower row from left to right). A non-programming media artist quickly built the alternatives by creating illustrations and including the according keywords for interaction into the filenames of an ordered image sequence. In fact, this way we found that shaking the device in this situation has been experienced as unnatural and difficult by test users. With the help of MockAR, such ideas could be tested and filtered in an early phase of development, when implementation of the more complex interactions was yet to be done. Also other quick prototyping of UI element positions and the sequencing and duration of video snippets saved time in the collaboration with the programmers. MockAR was also tested in a student project involving four non-programmers in AR application design. Due to the simplified approach, they were able to build alternative design interactions within 20 minutes each. After building a series of designs, Mock-ARs users requested further functionalities regarding non-linear playback and gesture input, which will be set on the development agenda.

Conclusion

MockAR has been developed as a side endeavor that became necessary within the project SPIRIT, while designing for a complex and novel user interaction in location-based AR with handheld devices. As recently, this area of development appears to prosper as a new field for media designers, easy-to-use prototyping tools for non-programmers are needed. MockAR established an iterative and interdisciplinary design and communication process within the project, which proved to be more difficult when designers had to wat for implementation by the AR developers.

Fig. 1 .

 1 Fig. 1. Early functional prototype of the SPIRIT application

Fig. 2 .

 2 Fig. 2. Mockup UI evaluation indoors (left) and outdoors (right).

Fig. 3 .

 3 Fig. 3. Example user interactions from left to right: tap, shake, pitch, turn left & turn rightUtilizing devices' sensor data, we use basic Android Software Development Kit[START_REF]Sensors Overview in Android Software Development[END_REF] functions to access device coordinates, such as of the accelerometer for detecting movements in landscape mode, as well as the camera2 package for capturing video used as AR background overlaid by a FrameLayout displaying transparent PNG images. Images are kept in a specific folder on the device's SD-card. After reading file names and finding interaction keywords, a listener on specified device sensors or the timer in milliseconds is set. Figure3shows user interactions, and Figure4user interaction keywords in the last six characters of the image file name. MockAR displays the transparent PNG image files from left to right.

Figure 3

 3 shows user interactions, and Figure 4 user interaction keywords in the last six characters of the image file name. MockAR displays the transparent PNG image files from left to right.

Fig. 4 .

 4 Fig. 4. Image file names with specifying user interaction keywords

Fig. 5 .

 5 Fig. 5. Two alternative actions to evoke the visualisation of spirits, tested with MockAR

Acknowledgements

This work has been funded (in part) by the Federal Ministry of Education and Research (BMBF) in Germany (03FH035PA3). We thank all project members for their support.


Bernhard Maurer

Michael Lankes
email: michael.lankes@fh-hagenberg.at

Barbara Stiglbauer
email: barbara.stiglbauer@jku.at

Manfred Tscheligi

EyeCo: Effects of Shared Gaze on Social Presence in an Online Cooperative Game

Keywords: Cooperative Games, Gaze-based Interaction, Social Presence, Shared Gaze 1

This paper investigates the effects of a shared gaze approach on social presence in an online cooperative game. We explored how a shared gaze visualization changes how players work together and form collaborative strategies based on different combinations of gaze interaction and verbal communication. Our study findings highlight the positive influence of a shared gaze visualization on team cohesion and involvement towards increased perceived social presence among cooperating team members. With our findings we want to inform game designers with insights on the inclusion of gaze-based interaction in remote gaming settings and whether this can strengthen the social bond between players. Our approach aims at fostering social couplings in remote collaborative gaming and investigates their potential to increase the connectedness between players.

INTRODUCTION

Playing games is an activity that is embedded in social and situated practices [START_REF] Sjöblom | Gaming as a situated collaborative practice[END_REF]. Game experiences are often driven by a certain social context where the presence of other players is an integral part of enjoyment. This results in social interactions between players (e.g., coordination of actions or encouraging another player) that are deeply rooted in natural human communication. In human-human collaboration gaze and eye contact are crucial factors building the foundation for social interaction [10, p.86] and information flow [9, p.67]. However, in remote settings, like online coop games, typical interpersonal means of face-to-face communication (e.g., gaze, mimic, etc.) that are prevalent in co-located gaming, are not or only limitedly present. These non-verbal signals have an impact on social presence and manifest themselves in various ways like facial expression, gesture, head movement, body posture, etc., which are factors that can also influence how players perceive each other in cooperative gameplay. This is especially relevant in games that require players to act cooperatively in order to be successful. In cooperative gameplay social interactions are often targeted at creating a shared understanding of the current scene and to coordinate each other's actions. We argue that gaze interaction can play an important part in how such cooperative actions are coordinated and thus, also influences social presence.

The approach discussed in this paper uses a game in combination with a shared gaze visualization as a shared embodied resource in order to foster social presence and connectedness between players. By giving the gaze of a cooperating player a "body" and a representation within the game we aim at exploring this gaze-based interaction modality as a means for collaboration. We argue that by providing a means of non-verbal communication (i.e., a shared gaze visualization) within a game, even if not actively part of the gameplay itself, a new layer of non-verbal communication for the players is created, that can result in new forms of human-human collaboration in online games.

In this paper, we investigate the impact of a shared gaze on social presence in a remote cooperative game setting. Further, we want to find out how a shared gaze visualization changes how people collaborate (e.g., different strategies) and how it is used in combination with other communication modalities like verbal input. We aim at using gaze as a "moderator" and facilitator of cooperation, and use shared-gaze as a way to create a coupling between players in order to foster a shared sense making process towards increased social presence. With our findings we want to inform game designers with insights on how and why the inclusion of gaze-based interaction in remote game settings fosters the social bond between players.

Social presence in online games

Several authors share the opinion that presence is composed of the three dimensions: social presence, spatial presence, and self presence [e.g, 20]. As this work specifically focuses on the social aspect of presence a more elaborated definition of the term shall be given. The concept of social presence was introduced by Short at al. and defined as "the degree of salience of the other person in the interaction and the consequent salience of the interpersonal relationships" [17, p. 65]. The researchers claimed that communication medium has an impact on the intimacy and immediacy. After Bulu [START_REF] Bulu | Place presence, social presence, co-presence, and satisfaction in virtual worlds[END_REF] theories based on the work of Short et al. explain that the level of social presence increases as the communication capabilities of the medium increases, ranging from text-based, to face-to-face media or to computer mediated communication. Following Hudson & Cairns [START_REF] Hudson | Interrogating social presence in games with experiential vignettes[END_REF] social presence can be compared with the concept of "Shared Involvement", coined by Calleja [START_REF] Calleja | In-Game: From Immersion to Incorporation[END_REF]. Shared Involvement can be understood as a sense of being with subjects in a common environment, whether that involvement is composed of explicit communication, acting as a team, or by being aware that one's actions are taking place in a shared environment. Regarding the role of social presence in the context of games Hudson & Cairns [START_REF] Hudson | Interrogating social presence in games with experiential vignettes[END_REF] emphasize the importance of social presence by noting that social relationships between players as mediated by games (as well as social presence as its foundation) have a significant influence on the gaming experience. This does not only apply to massively multiplayer games but also to console & PC games (multiplayer, co-located play, etc.). Cairns et al. [2, p.1069] state that "playing socially is a prevalent and important aspect of digital gaming." Furthermore, several studies identified a correlation between a positive game experience and a high degree of social presence and social interaction (e.g., [START_REF] Gajadhar | Influence of social setting on player experience of digital games[END_REF][START_REF] Maurer | Gaze-Based Onlooker Integration: Exploring the In-Between of Active Player and Passive Spectator in Co-Located Gaming[END_REF]).

Nonverbal Interaction and Gaze-based Interaction in Games

Nonverbal communication manifests itself in a variety of forms such as facial expression, gestures, paralinguistic, body language and posture, proxemics, haptics, and gaze [START_REF] Dunning | Research in nonverbal communication[END_REF]. Several studies revealed that there is a relation between social presence and nonverbal communication [START_REF] Kaye | Exploring flow experiences in cooperative digital gaming contexts[END_REF]. Mansour et al. [START_REF] Mansour | Building a bi-directional bridge between social presence and interaction in online games[END_REF] argue that there is a positive relationship between the perception of social interaction (reciprocal processes in which humans negotiate and regulate the quality of their relationships) and the feeling of social presence in online multiplayer games. The authors note that the coordination of a conversation within games (e.g., clarifying mutual goals, discussing strategies, tactics, etc.) is a dynamic and complex process including exchanges of nonverbal communication. Their proposed framework shows that both verbal and nonverbal communication acts are two main components of social interaction among players. After Mansour et al. [START_REF] Mansour | Building a bi-directional bridge between social presence and interaction in online games[END_REF] the application of verbal and nonverbal behavior helps players to familiarize with their partners, fosters the management of the interaction flow and has a positive influence on the feeling of trust among players. Manninen and Kujanpää [START_REF] Manninen | Non-verbal communication forms in multi-player game session[END_REF] suggest that an efficient combination of different communication channels enhances interaction among players. By combining various forms of interaction players would not have to rely on verbal communication alone, but have more flexible means in representing themselves and their ideas. Further, Shahid et al. [START_REF] Shahid | Video-mediated and co-present gameplay: Effects of mutual gaze on game experience, expressiveness and perceived social presence[END_REF] investigated the effects of mutual gaze on the game experience and perceived social presence during video-mediated and co-present gameplay. Their results indicate that the absence of mutual gaze dramatically affects the quality of interpersonal interaction in video-mediated gameplay settings. Including mutual gaze interaction in such a setting, on the other hand, leads to increased social interaction and mutual understanding among remote collaborators. They argue for the inclusion of mutual gaze interaction as an integral part of playful cooperative settings.

Contribution

Based on related research, we argue that there is much potential for gaze-based interaction in cooperative online gameplay. Research on gaze interaction is rather limited in the context of cooperative online gaming. Besides using gaze as a substitute and as enrichment for interaction we want to investigate whether the non-diegetic use of a shared gaze visualization can support social interaction in remote collaborative gameplay. In contrast to other research, we see gaze communication as an integral part of the gaming experience and explore its potential to be used as a means of explicit and implicit interaction. Further, we explore how a shared gaze visualization changes cooperative in-game communication and how teams appropriate the use and meaning of it.

We aim at using gaze as an input method to foster social presence and enhance team collaboration. We argue that by providing this additional communication channel in an online co-op can potentially increase connectedness between cooperating players. In that regard, the game acts as a mediatory artifact generating a social bonding between the cooperating team of players. In a remote setting, typical human face-to-face qualities and non-verbal communication (e.g., eye contact) is very limited. Incorporating eye-based interaction during cooperative online play (in our case visualizing another person's gaze point on a player's screen) can potentially enrich such remote co-op settings. With our approach and gaze-based interaction concept we aim at providing nonverbal information without distracting players but to support them in their gaming activities and explore shared gaze as a subconscious and implicit means of communication but also as an explicit tool for cooperation.

Experiment Description

In order to explore gaze-based collaboration in an online co-op game, we conducted an experiment that investigates the effects of shared gaze visualizations on social presence among the participants. The main idea behind the experiment was to visualize the cooperating person's gaze on the player's screen and vice versa (see Figure 1). We chose the game Ibb & Obb [START_REF]Ibb & Obb[END_REF] as a test bed for our experiment and gaze-based interaction concept. Ibb & Obb is a 2D platformer that lets two players cooperate online to succeed the different puzzle based levels. In this game, players have to coordinate each others actions quite carefully to be able to finish the puzzles the game presents. The experiment consisted of four conditions with varying communication modalities for the cooperating players which were completely randomized to the participants (i.e., randomized block factorial design): 1) no additional communication channels (condition name: none), 2) verbal communication (condition name: voice), 3) gaze (condition name: gaze), and 4) verbal communication + gaze (condition name: voice and gaze). In conditions with shared gaze (i.e., condition 1 and 3), the gaze of the other player (i.e., where the other player is currently looking at) was visualized in real-time on the other player's screen as a black circle (see Figure 1, right picture). In conditions 2 and 3 participants could additionally communicate via online voice chat. After every playing condition, participants filled out a questionnaire regarding social presence (see section on Measures). The participant pairings played the levels of the game in ascending order to assure that players are always confronted with an increasing level of difficulty. The playing condition of every level was randomized for every participant pairing.

With this study experiment we wanted to investigate the following hypothesis: With the integration of gaze interaction (i.e., the visualization of the other person's gaze) in online co-op games, subjects will experience an increased level of social presence in comparison to a gaming scenario that is solely based on verbal and in-game interactions. We argue that with shared gaze, players receive an additional communication channel that is either used consciously or unconsciously, but which in any case, provides a means of non-verbal communication that is deeply rooted in natural human face-to-face communication. This potentially effects social presence during online coop play and gives players a new tool to be used for e.g., in-game spatial referencing.

Participants and Procedure

The study was conducted at two separate research facilities. The sample consisted of 20 participants), age 21 to 37 years (6 female, mean age= 26.20, SD= 4.51). All participants were either students of the University of Applied Sciences Upper Austria (65%) or research staff working at the University of Salzburg (35%). Furthermore, subjects represented a variety of disciplines of education having a background in psychology, software engineering, or in digital arts. About half of the participants (11 persons) share an affinity to play video games as they indicated to play games at several times a week or daily, whereas only one participant stated to never play games.

Each evaluation session consisted of two subjects that played the game collaboratively in two separate rooms. The evaluation was divided into four parts based on the previously described conditions (none, voice, gaze, gaze and voice). By choosing a within-subject design, all participant teams had to play each of the mentioned scenarios (play time limit for each condition: 5 minutes). The order in which the teams were assigned to the conditions was randomized to limit the effects of the condition and game difficulty. As a first step, the experimenter provided a short introduction to give an overview of the overall procedure. After the eye tracking devices were calibrated the evaluation part started with a sandbox level ("limbo" level with level selection) showing the basic means of interaction. Participants were instructed about the setting and the game goals. As the control scheme and the genre itself (i.e., platform game) were easy to comprehend, subjects had no difficulties to get into the game. When subjects confirmed that the control scheme of the game was clear to them the experiment began. All subjects started with the first game level of Ibb & Obb in conjunction with one of the four conditions, followed by level 2, 3 and 4. After each level the condition was changed. For example, team 1 started the experiment with level 1 and the gaze condition, while team 2 played level 1 with the voice condition. This should enable players to get into the game (no steep learning curve), as well as make sure that at the beginning of the experiment subjects were not confronted with too difficult game situations.

After every condition, participants were instructed to fill out the CCPIG questionnaire (see section on Measures for a detailed description). After finishing all conditions, participants had the possibility to give comments on the played conditions with a focus on social presence and their experience with the gaze visualization, via a team interview carried out by the experimenter. One experimenter was present during the whole study and took notes on observations and participants' interactions in every condition (i.e., how they used the gaze visualization and potential collaboration strategies emerging from the gaze visualization). The procedure took between 50 to 60 minutes.

Technical Setup

The technical setup for our experiment consisted of two Tobii EyeX eye trackers (http://www.tobii.com/xperience/) and two separate applications, one for data communication and another one for gaze visualization on each player's computer. The gaze position of a player (i.e., X and Y in screen coordinates) was captured by the eye tracker and visualized in real-time on the corresponding players screen "above" the actual game. The communication between the eye tracking application on one player's side and the gaze visualization on the other player's computer was realized via Spacebrew (docs.spacebrew.cc), which is an open-source websocket-based prototyping framework. In order to provide a smooth movement of the gaze visualization, we filtered the gaze point values before sending them to the visualization application. Figure 2 illustrates the overall technical setup.

Measures

To measure the social presence dimensions the Competitive and Cooperative Presence in Gaming Questionnaire (CCPIG v1.2), which is a validated scale developed by Hudson & Cairns [START_REF] Hudson | Measuring Social Presence in Team-Based Digital Games. Interacting with Presence: HCI and the Sense of Presence in Computer-mediated[END_REF], was employed. We decided to use this questionnaire, because it specifically aims at exploring social presence in the complex social environments that are team-based online games. It focuses explicitly on games and is not designed to be a general measure for social presence across multiple media. The CCPIG is composed of two parts: part 1 measures competitive social presence, which is the level of social presence experienced by players towards their opponents. The second part measures cooperative social presence, the level of social presence experienced by a participant towards their teammates. The authors of the questionnaire note that it is possible to use the two parts independently to investigate different kinds of games (competitive, cooperative). Since the game of our evaluation features cooperative and not competitive gameplay, we applied only the second part of the CCPIG. This part is made up of two modules. The first module measures the perceived level of team cohesion (25 itemsexample: "It was as much about the team as about my own game"), while module 2 measures team involvement (11 items -example: "The actions of my teammates affected my thoughts and actions"). All items were rated on a five-point Likert scale

Spacebrew Server Sends x,y screen coordinates of gaze

Receives and draws gaze point data

PC Eye Tracking Application

Java Application with Visualization

Player 1 Player 2

PC

Eye Tracking Application

Java Application with Visualization

Eyetracker Eyetracker (ranging from 1 = "strongly disagree" to 5 = "strongly agree"). The internal consistencies were acceptable to good with Cronbach's alpha reliability estimates ranging from α = .67 to α = .92 (cf. Table 1). Apart from the CCPIG the evaluation also included an open interview at the end of the test session in order to gain a deeper understanding of the game experience and how participants perceived the gaze interaction. Participants were asked if the gaze visualization was a helpful tool to interact with their teammate as well as how they used it for communication. Additionally, the participants were asked if they felt their teammate as being more present in conditions with a gaze visualization and if they had any suggestions for improvements in regard to game design and the usage of the gaze visualization.

Data Analysis

All dependent variables were normally distributed, meeting the requirements for parametric analyses. Hence, data were analyzed by means of a repeated measure analysis of variance (rANOVA) with the experimental condition (4 conditions) as the withinsubjects factor and the 2 indicators of social presence (team cohesion and team involvement) as the dependent variables. To account for violations in sphericity, the Greenhouse-Geisser correction of degrees of freedom was employed. Post hoc analyses on mean differences between each pair of the four conditions were conducted using Sidak's method. The conventional level of p < .05 was used when evaluating the results with regard to statistical significance. Note. N = 20. † p < .10, * p < .05. Gender: 0 = male, 1 = female. Occupation: 0 = student, 1 = employed. Playing games: 1 = never, 2 = occasionally, 3 = several times a week, 4 = daily. 1 = condition without gaze and voice, 2 = voice, 3 = gaze, 4 = gaze and voice.

Results

Table 1 reports the descriptive statistics and bivariate Pearson correlation coefficients between the variables. As expected, participants experienced higher levels in social presence in conditions with additional communication channels. Social presence was highest in conditions where voice communication was possible (i.e., conditions 2 and 4). Gender was not significantly related to social presence, but age was associated with higher levels in social presence, particularly in the voice condition. Moreover, the more frequently participants were playing games, the less team involvement they were experiencing in the condition without gaze and voice communication. The results of the rANOVA revealed a significant main effect of experimental condition, F(1.61, 35.70) = 12.42, p < .001, and a significant interaction effect between experimental condition and the social presence indicators, F(1.88, 35.70) = 6.03, p = .006. Both effect sizes were large with part. ɳ² = .40 for the main effect and ɳ² = .24 for the interaction. Thus, social presence differed significantly between experimental conditions (main effect), and the effects of the experimental condition were different for team cohesion and team involvement (interaction effect). Figure 3 illustrates the results.

Although condition 3 (gaze) had higher ratings than condition 1 (none) post hoc tests regarding the main effect of experimental conditions demonstrated that condition 3 (gaze) did not result in significantly higher social presence experiences as compared with condition 1 (none), M difference = 0.11, SE difference = 0.07, p = .613. Moreover, condition 4 (voice + gaze) was significantly superior to condition 3 (gaze), M difference = 0.36, SE difference = 0.09, p = .003, but not to condition 2 (voice), M difference = 0.06, SE difference = 0.05, p = .894. In sum, these results suggest that adding gaze as a communication channel tends to have positive effects on social presence experiences of players, however not significantly, which is contrary to expectations. As far as the interaction effect is concerned, post hoc analyses revealed that the effect of the experimental condition was stronger for team cohesion as the dependent variable, ɳ² = .44, than for team involvement, ɳ² = .25. The differential effects of the experimental condition on team cohesion and team involvement became particularly evident when conditions 2 (voice) and 4 (voice + gaze) were compared with condition 1 (none): Team

3,5 4 4,5 5 1 (None) 2 (Voice) 3 (Gaze) 4 (Voice + Gaze)

Social Presence

Experimental Condition

Cohesion Involvement cohesion could be significantly improved by adding voice, M difference = 0.54, SE difference = 0.13, p = .003, or voice and gaze as communication channels, M difference = 0.57, SE dif- ference = 0.15, p = .007. On the other hand, team involvement was significantly higher when voice and gaze were added simultaneously, M difference = 0.36, SE difference = 0.12, p = .045; adding voice only tended to be superior to condition 1 as well, but this difference failed to reach significance, M difference = 0.27, SE difference = 0.10, p = .090.

Data Results

The qualitative data consisted of the answers from the team interviews as well as observations and notes taken during the study. The notes were assigned to one of four predefined categories (i.e., one for every condition) to gather the study observations in a structured way. During the study the observing experimenter wrote down how participants coordinated their actions (e.g., potential strategies) in every condition and what instructions they gave to each other (e.g., either through gaze or verbal communication).

The observation data as well as the team interview after the playing sessions was analysed according to the basics of qualitative content analysis [START_REF] Mayring | Qualitative Content Analysis[END_REF] in order to identify "common themes" and similarities among the participant teams in every condition.

The observations as well as the interviews showed that in conditions where voice communication was enabled (i.e., condition voice + gaze and condition voice), voice was the dominant information channel for the teams. Voice was used to negotiate actions, coordinate planning, turn taking, potential hazards, avatar capabilities etc. Further, teams also reported that they felt less verbal misunderstandings in the condition that combined gaze and voice input. This suggests a positive effect of the gaze visualization towards gaining a shared understanding among the team members. For instance, when the teams encountered new, yet unexplored level areas, players stopped their avatars, discussed and planned together, before executing the negotiated actions in a cooperative manner ("I think you have to jump right up there and then I can reach over here"). This step-by-step planning was supported by the gaze visualization as it was used to draw paths showing the team member how to proceed and link verbal input with spatial referencing. The more communication channels the teams had (within the different conditions), the more "planning ahead" occurred. In contrast to that, the condition with no additional communication channels (i.e., condition none) appeared to be most prone to trial and error behavior of the teams.

During the interviews, 9 out of 10 teams reported, that compared to the condition with no additional communication channels (i.e., condition none), conditions with a shared gaze visualization made them perceive the other player as being "more present". They reported that they tried to use the gaze visualization as a tool for communication, e.g., for pointing reasons to show the team member where to move. However, some participants felt that using the gaze as a tool was too difficult, as the meaning of, e.g., potential movements and gestures drawn via the visualization, could not be negotiated in advance with the teammate, thus, tended to be unclear to them. Further, the players' gaze was naturally more focused on their own avatar, except when they tried to use the gaze visualization as a tool for pointing and turn taking, in order to draw the other player's attention to something. The concept of perceiving the gaze visualization as a mere tool and not as a representation of the other player may also explain why the effect of social presence was not as pronounced as anticipated. Some players noted that it would be a good idea to visually link the other player's game character with the gaze information. A detailed discussion on the design possibilities in this regard can be found in Lankes et al. [START_REF] Lankes | Whom are you looking for?: the effects of different player representation relations on the presence in gaze-based games[END_REF]. An issue participants had with the gaze visualization was its "always-on" behavior. They felt a strong loss of meaning in the partner's gaze visualization as it was constantly visible, thus, making it hard to distinguish between deliberate communication and unwanted inputs. In that regard, players highlighted that for future iterations of the prototypes they would like to see both, their own and their partner's gaze visualized, a visual link between the avatar and the gaze information, as well as having a way to activate/deactivate the visualization when necessary.

Discussion & Lessons Learned

Our study has shown, that gaze-based interaction bears much potential as an additional layer of collaboration in games with shared gaze showing positive influence on perceived social presence. We explored how the non-diegetic use of a shared gaze visualization can support social interactions in a remote setting. It proofed to be a viable means for communication, however, it needs improvements to act as a useful tool for explicit interaction and communication.

Gaze input needs affordances and activation strategies:

In our prototype the partner's gaze was visualized in an abstract manner (i.e., via a black circle) without giving the gaze point a semantic meaning within the game world. We did this in order to explore how people react to this new interaction modality and how its use and meaning will be negotiated by the teams themselves letting the players freely appropriate the gaze input towards facilitating common ground. However, a crucial aspect towards making gaze a useful "tool" is to provide a certain affordance and meaning in order to let the players know how and when to use it appropriately. This could be done by, e.g., integrating the gaze point directly into the game world (e.g., letting avatars react to the gaze point) to assure that there is no disconnect between in-game interactions and player interactions. Additionally, one of the lessons learned from the study was that players didn't like the "always-on" aspect of the prototypes current implementation of the gaze visualization. Thus, we argue, that in order to be adopted as a tool by players, we also need to design for meaningful and understandable ways of activation of such a gaze-based interaction (e.g., the player can trigger the visualization actively).

Gaze as an additional layer of communication supporting team processes: Players used their gaze as a tool for communicating in situations that required e.g., exact pointing, or as a substitute to verbal interaction to establish a shared understanding between players and lessen the occurrence of misunderstandings due to potential ambiguous verbal communication. The more communication channels the teams had, the more negotiation between players was happening. This notion of gaze as an additional communication layer could in turn help players to connect and communicate with each other, e.g., in game settings where verbal input might be undesired but team coordination is still necessary (e.g., cooperative mobile online gaming in a public transport scenario).

Gaze as a subconscious non-verbal communication channel: Besides explicit gaze interactions like pointing, we believe that players can also form a kind of subconscious communication through an omnipresent gaze visualization of the other player. Over time players could potentially learn to understand the gaze movements and resulting gestures and intentions of another player, which could lead to a more integrated visual "team language" and connectedness. If and how such implicit gaze-based communication is established between two remote cooperating players will be part of future work, though. In that regard, we plan to do a study in a similar setup with more participants over a longer period of time in order to investigate if such a shared gaze visualization can be used and "learned" over time as a subconscious means communication.

Limitations:

The questionnaire we used included many items regarding the players' feelings of acting together as a team. We are aware that the game we used in our study was already strongly based on working together as a team, which could have led to the increases in team coherence and presence in the questionnaire data being not significant among the different conditions. Although we found only little quantitative improvement in social presence between gaze and non-gaze conditions, post-play interviews nonetheless indicate that subjects reacted positively to the inclusion of shared gaze, particularly in conjunction with voice communication.

Conclusion

This paper reports on a study that investigated a shared gaze approach and its effects on social presence and collaborative interactions in online cooperative play. We explored different combinations of voice and gaze input as a communication channel for players during a team-based game. Our study findings show that shared gaze can have a positive influence on team cohesion and involvement, leading to players perceiving their team member as being more present when their partner's gaze is visualized. Participants tried to use the gaze visualization as a tool for communication, e.g., for spatial referencing, and described it as being a useful substitute to verbal communication. Based on our findings we argue, that shared gaze can foster social couplings in remote collaborative gaming settings which in turn can contribute to increased connectedness between collaborating players. The integration of such non-verbal interpersonal communication qualities such as gaze, is yet an underrepresented and underused design resource, but nevertheless, a promising direction for future game designs.

Figure 1 :

 1 Figure 1: Left side: Picture of study participant playing the game while eye tracking is used to communicate with the other player. Right side: In-game visualization of gaze point indicated via a black circle rendered above the actual game.

Figure 2 :

 2 Figure 2: Schematic of the technical study setup; Two separate applications sending and receiving gaze data for visualization within the game on each participant's side.

Figure 3 :

 3 Figure 3: Means of Social Presence in the four experimental conditions (error bars represent 95% confidence intervals).

Table 1 :

 1 Means, standard deviations, zero-order correlations, and Cronbach's alpha reliabilities (in the diagonal) of the studied variables.

	Variable	M	SD	1	2	3	4	5	6	7	8	9	10	11	12
	1. Gender	--	--
	2. Age	26.20	4.51	.19
	3. Occupation	--	--	.21	.80*
	4. Playing games	2.80	0.95	-.21	-.04	-.41 †
	5. Cohesion (1)	3.99	0.57	.11	.28	.16*	-.19	(.92)
	6. Involvement (1)	4.12	0.46	.16	.39 †	.53*	-.41 †	.70*	(.86)
	7. Cohesion (2)	4.54	0.27	.06	.54*	.63*	-.12	.24	.24	(.74)
	8. Involvement (2)	4.39	0.30	-.03	.55*	.53*	.04	.15	.16	.68*	(.67)
	9. Cohesion (3)	4.09	0.44	.30	.20	.39 †	-.22	.63*	.60*	.31	.41 †	(.87)
	10. Involvement (3)	4.23	0.38	-.06	.22	.34	-.09	.72*	.64*	.26	.44 †	.75*	(.85)
	11. Cohesion (4)	4.56	.031	.02	.16	.20	.11	-.06	-.03	.51*	.71*	.39 †	.30	(.82)
	12. Involvement (4)	4.48	0.33	-.26	.03	.04	.06	-.12	.10	.25	.70*	.20	.43 †	.74*	(.79)

Acknowledgements:

The financial support by the Austrian Federal Ministry of Science, Research and Economy, the Austrian Ministry for Transport, Innovation and Technology and the federal governments Vorarlberg, Salzburg, Steiermark is gratefully acknowledged (Comet -LiTech).


Amir Zaib Abbasi
email: amir_zaib_abbasi@yahoo.co.uk

Ding Hooi

Helmut Hlavacs

A Revisit of the Measurements on Engagement in Videogames: A New Scale Development

Keywords: Engagement, videogame engagement, consumer videogame engagement, cognitive engagement, affective engagement, behavioral engagement, reflective-formative model, scale development process. 1

This research article attempts to conceptualize and operationalize the concept of engagement in videogame-play as consumer videogame engagement that comprises both psychological and behavioral dimensions. Accordingly, this study has developed a scale for measuring consumer videogame engagement through following the steps of scale development. Next, the study has collected data on two samples. Besides, this study has applied SPSS 22.0 version and SEM-PLS approach to analyze the data on two samples and to validate the construct of consumer videogame engagement. Based on the study results, an instrument has proven to be a valid source for measuring engagement in videogames as well as a reflective-formative and multi-dimensional construct. This study contributes to the videogame literature as it considers consumer videogame engagement as a multi-dimensional construct comprising on cognitive, affective and behavioral engagement. It further validates the scale of consumer videogame engagement as reflective-formative model among videogame players.

Introduction

Literature indicates that several studies have put their efforts to develop an instrument to measure engagement in videogame playing. Among all the studies, a study by [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF], was the first research who developed an instrument to measure the subjective experience of videogame-play based on these dimensions "gameflow, cognitive-absorption and presence" and named it as game-experience questionnaire or GEQ. Another subsequent study done by [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF] who developed a scale named as game engagement questionnaire or GEQ with combination of four constructs "flow, presence, absorption and immersion" to measure player's engagement in videogame. Again, this study has also used almost similar dimensions as it was used in the following study [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF]. In similar vein, a recent study [START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF] has reviewed the model of game engagement construct given by [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF]. In this study, the author has discussed that three of the dimensions of game engagement questionnaire such as "flow, immersion and presence" [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF] are interrelated to the subjective experience of videogame-play but absorption is similar to flow construct so, it is better not to consider in the measurement of game-engagement questionnaire. According to [START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF], a new revised construct of game-engagement comprises the following dimensions "flow, presence, involvement and immersion" that can be applied to examine the subjective experience of videogame play.

Doing a critical review of prior researches that have developed and used engagement scale in their studies. The current study has concluded with the following limitations; first, this study finds that mostly studies have only considered psychological constructs (flow, presence and absorption) and have ignored the importance of using behavioral dimensions to examine the subjective experience of videogame play as well as measure the player' engagement in video games [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF][START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF]. Secondly, these studies have not properly conceptualized and operationalized the term engagement and immersion in their studies.

Moreover, several studies have stated that engagement in videogame, is a multidimensional construct [START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF][START_REF] Silpasuwanchai | Developing a Comprehensive Engagement Framework of Gamification for Reflective Learning[END_REF]. Among these studies, only a study by [START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF] who really captured the meaning of engagement on a multi-dimensional level. But, the problem with the following study [START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF] is, authors have misspecified the construct of game immersion as reflective-reflective construct (A reflective measurement model is; when items share a common theme, items are exchangeable and deleting or adding an item does not change the conceptual meaning of the construct [START_REF] Jarvis | A critical review of construct indicators and measurement model misspecification in marketing and consumer research[END_REF]) on first and second order construct. Rather, the construct of game immersion seems to be as reflective-formative construct that means reflective on first order and formative on second order construct (A formative measurement is; when items do not require to have a shared common theme, items are not replaceable and deleting and adding an item can change the conceptual meaning of the construct [START_REF] Jarvis | A critical review of construct indicators and measurement model misspecification in marketing and consumer research[END_REF]). The decision behind calling a game immersion construct as reflective-formative was drawn on basis of reviewing the following study [START_REF] Jarvis | A critical review of construct indicators and measurement model misspecification in marketing and consumer research[END_REF] that has discussed the important decision rules for specifying the construct as reflective or formative.

Therefore, the current study considers the limitations of past studies and takes an initiative to first conceptualize and operationalize the term engagement in videogames as "consumer video-game engagement" and develops a new scale with combination of psychological as well as behavioral dimensions in order to measure engagement in videogame-playing in more advanced level. Moreover, this study aims to validate a newly developed construct among the videogame consumers. The present study is first in videogame literature which considers both psychological and behavioral dimensions for measuring consumer video-game engagement. Secondly, this study considers the importance of both reflective and formative constructs in explaining and measuring the construct of consumer videogame engagement on higher order construct. Thirdly, this study applies the concept of marketing and consumer research, especially the definition of consumer engagement and its related dimensions (cognitive, affective and behavioral) that have been discussed in the following studies [START_REF] Brodie | Customer engagement: conceptual domain, fundamental propositions, and implications for research[END_REF][START_REF] Hollebeek | Demystifying customer brand engagement: Exploring the loyalty nexus[END_REF] in order to conceptualize and operationalize the construct of consumer videogame engagement.

Conceptualization of Consumer Videogame Engagement

This study follows the definition of engagement given by [START_REF] Brodie | Customer engagement: conceptual domain, fundamental propositions, and implications for research[END_REF][START_REF] Hollebeek | Demystifying customer brand engagement: Exploring the loyalty nexus[END_REF] as "Engagement is a multidimensional construct which is subject to a context-specific expression of relevant cognitive, emotional, and behavioral dimensions". The author of the study [START_REF] Hollebeek | Demystifying customer brand engagement: Exploring the loyalty nexus[END_REF], has further added that engagement is a process which reveals as a result of two-way communications between the engagement-subject (consumer/customer) and a particular engagement-object such as a product, service or a brand, which leads to generate consumer engagement states (cognitive, affective and behavioral). On the basis of above stated definition, this study conceptualizes consumer videogame engagement as "A psychological state that triggers due to two-way interactions between the consumer and videogame product, which generates different level of consumer engagement states (cognitive, affective and behavioral)".

Scale Development and the Validation of Consumer Videogame Engagement

This study adopts the scale development procedure given by [START_REF] Churchill | A paradigm for developing better measures of marketing constructs[END_REF][START_REF] Tsaur | Destination brand identity: scale development and validation[END_REF]. This study first compiles the measurement scales as already reported in the literature which is specifically relevant to the following dimensions: conscious-attention, absorption (cognitive engagement), dedication, enthusiasm (affective engagement), social interaction and interaction (behavioral engagement). The items on the following dimensions such as conscious attention, six items (Items 1 to 6) from [START_REF] Vivek | A generalized multidimensional scale for measuring customer engagement[END_REF], item7 from [START_REF] Qin | Measuring player immersion in the computer game narrative[END_REF] and item8 from [START_REF] Wiebe | Measuring engagement in video game-based environments: Investigation of the User Engagement Scale[END_REF] are adapted in this study. Absorption scale adapted from [START_REF] So | Customer engagement with tourism brands scale development and validation[END_REF]. Whereas, dedication items as item1 from [START_REF] Schaufeli | The measurement of engagement and burnout: A two sample confirmatory factor analytic approach[END_REF] and item2 to item7 from [START_REF] Cheung | Promoting sales of online games through customer engagement[END_REF] and the items of enthusiasm are adapted from the study of [START_REF] Vivek | A generalized multidimensional scale for measuring customer engagement[END_REF]. However, social connection scale is adapted as item1 to item4 from [START_REF] Vivek | A generalized multidimensional scale for measuring customer engagement[END_REF] and remaining items 5,6 and 7 from [START_REF] Kemp | Engaging consumers in esthetic offerings: conceptualizing and developing a measure for arts engagement[END_REF]. Finally, interaction scale is adapted from [START_REF] So | Customer engagement with tourism brands scale development and validation[END_REF]. Overall, the study has generated 39 items, which were further evaluated for the content validity by 4 PhD students and two experts to assess the content of consumer videogame engagement. Based on their comments, this study has revised certain items.

For first-time data collection, 200 questionnaires were distributed among university teenage students who play videogames aged 16-19, out of which 160 questionnaires were returned with a response rate of 80%. Out of 160 questionnaires, 134 valid cases were left after treating the missing values and biased responses. The data were further analyzed for exploratory factor analysis (EFA) as well as for internal consistency and the results are shown in the Table1. After finding the satisfactory results, this study continued to second-time data collection, 350 questionnaires were distributed and collected 290 responses with response rate of 83%. After treating missing values and biased responses, we were left with 265 valid cases that were used for further analysis.

SEM-PLS (Structural equation modeling-partial least squares) was employed to validate the construct of consumer videogame engagement because, it has both reflective and formative constructs [START_REF] Hair | PLS-SEM: Indeed a silver bullet[END_REF]. For reflective construct, this study involves the estimation of internal consistency, convergent validity and discriminant validity. Whereas, the evaluation of a formative construct follows different guidelines like testing of multicollinearity, indicator weights, and redundancy analysis.

Initially, a reflective measurement model was assessed for its convergent validity and achieved confirmatory factor loadings (CFA) greater than 0.70, composite reliability ranged from 0.89 to 0.92, while AVE were in between 0.61 to 0.75. All criteria of convergent validity were met. Discriminant validity was evaluated through newly introduced method called Heterotrait-Monotrait ratio (HTMT) of correlations [START_REF] Henseler | A new criterion for assessing discriminant validity in variance-based structural equation modeling[END_REF] and found that all values have passed the critical value of HTMT .85 as in Table 2.

This study has assessed the three criteria for the evaluation of formative measurement model as suggested by [START_REF] Hair | A primer on partial least squares structural equation modeling (PLS-SEM)[END_REF]. The first criteria is to assess the convergent validity also termed as redundancy analysis. The results indicate that the path coefficient between consumer video-game engagement and global measure is 0.826, which is higher than the threshold value of 0.80 as recommended by [START_REF] Hair | A primer on partial least squares structural equation modeling (PLS-SEM)[END_REF] and thus, depicting that the formative constructs have achieved the convergent validity. Second, the study has checked the collinearity issues and found that there is no multicollinearity issue because, all values shown in the Table 3, are below the threshold value of 5 as suggested by [START_REF] Hair | A primer on partial least squares structural equation modeling (PLS-SEM)[END_REF]. Third, this study has assessed the significance of indicator weights as shown in the Table 3 and found that formative constructs are highly significant at 0.00 level.

Conclusion

This study first conceptualized operationalized the construct of consumer videogame engagement then developed a scale for measuring consumer video-game engagement. The scale was first validated through EFA and reliability test. Second, the data were recollected on more respondents for measuring CFA and reflective measurement model on first order. All results met the criteria for the assessment of reflective measurement model then second order were created on a formative level. Formative measurement model was assessed on basis of three criteria given by [START_REF] Hair | A primer on partial least squares structural equation modeling (PLS-SEM)[END_REF] and results met the criteria for the evaluation of a formative model.

Table : 1 Shows Results of Both First and Second Time Data Collection

 :

			Study one: N=134	Study two (N=265): Convergent
						Validity
			EFA	C.Al	CFA	C.Al
	Construct	Items	Loadings	pha	Loadings	pha	CR	AVE
	Absorption	When I am playing this video-game, I forget everything else around me.	0.82	0.83	0.73	0.84	0.89	0.61
		Time flies when I am playing this video-game.	0.63		0.73
		When I am playing this video-game, I get carried away.	0.93		0.83
		It is difficult to detach myself from playing this video-game.	0.82		Deleted
		When I am playing this video-game, I feel immersed.	0.48		0.80
		I feel happy, when I am playing this video-game intensely.	Deleted		0.81
	Conscious Attention	I like to know more about this video-game.	0.87	0.89	Deleted
		I like to learn more about this video-game.	0.92		0.82	0.88	0.92	0.74
		I notice information related to this video-game.	0.83		0.85
		I pay a lot of attention to anything about this video-game.	0.74		0.88
		I keep up with things related to this video-game.	0.65		0.88
	Dedication	This video-game inspires me.	0.71	0.84	0.84	0.86	0.91	0.71
		I am enthusiastic about playing this video-game.	0.85		0.85
		I am proud of playing this video-game.	0.65		0.84
		I find this video-game full of meaning and purpose.	0.84		0.84
		I am excited when playing this video-game.	0.82		0.82

Table 2 : Discriminant Validity (HTMT Ratio)

 2

		Absorp	ConsAtten	Dedicate	Enthusi	Interact	SocialConn
	Absorp
	ConsAtten	0.683
	Dedicate	0.656	0.836
	Enthusi	0.806	0.73	0.697
	Interact	0.582	0.618	0.654	0.661
	SocialConn	0.414	0.576	0.46	0.561	0.621

Table 3 : Evaluation of Formative Constructs Construct Scale Measurement model Items Weights Full Collinearity (VIFs) T - Values P-Values

 3

	Enthusiasm	I spend a lot of my discretionary time playing this video-game.	0.8	0.85	0.75	0.86	0.90	0.65
		I am heavily into playing this video-game.		0.91		0.85
		I am passionate about playing this video-game.		0.67		0.84
		I enjoy spending time playing this video-game.		0.52		0.81
		I try to fit playing this video-game into my schedule.	0.85		0.77
		In general, I like to get involved in the discussions about this video-game
	Interaction	playing.			0.75	0.88	0.83	0.88	0.91	0.68
		I am someone who enjoys playing this video-game with others like-minded
		video-game players.			0.73		0.81
		I am someone who likes actively participating in the discussions about this
		video-game playing.			0.95		0.87
		In general, I thoroughly enjoy exchanging ideas on this video-game with
		other video-game players.			0.84		0.82
		I often participate in activities relating to this video-game.	0.77		0.79
	Social Connection I love playing this video-game with my friends.		0.91	0.86	0.89	0.83	0.90	0.75
		I enjoy playing this video-game more when I am with others.	0.91		0.85
		Playing this video-game is more fun when other people around me play it
		too.			0.88		0.86
		I receive social fulfillment from playing this video-game.	0.59		Deleted
		Cognitive Engagement	Formative	Absorption	0.40	3.1	3.16		0.00
				ConsAtten	0.71		6.91		0.00
		Affective Engagement	Formative	Dedication	0.50	3.3	4.90		0.00
				Enthusiasm	0.62		6.12		0.00
		Behavioral Engagement	Formative	Interaction	0.78	1.7	10.15		0.00
			Social connection	0.34		3.51		0.00


Alexander Golombek

Michael Lankes

Jürgen Hagler
email: juergen.hagler@fh-hagenberg.at

Vancouver Maneuver: Designing a Cooperative Augmented Reality Board Game

Keywords: augmented reality, board games, co-located play

In this paper we present Vancouver Maneuver, a game for mobile devices using Augmented Reality software to create a cooperative board game experience. Utilizing principles from both digital and analogue board game design, a hybrid game design approach is proposed in order to identify applicable mechanics. By doing so we combine the physical and social aspects of co-located tabletop gaming with the computing power and aesthetics of digital games.

Introduction

With recent developments in the field of smartphones or tablets, the market for mobile computer games is still growing. Technological improvements, both regarding computing power and the handling of advanced 3D graphics, make it possible for game developers to create games with demanding hardware specifications in mind. Current generations of mobile devices even allow Augmented Reality (AR) applications to be available for a majority of smartphone users.

According to Zagal et al. [START_REF] Zagal | Collaborative Games: Lessons Learned from Board Games[END_REF] all games have their roots in the physical world, whether it is sports on wide fields or strategical board games with game pieces. While digital games tend to be more solitary and are experienced individually, traditional games are often played with others. When looking at digital games, the majority of games are played on desktop computers or game consoles, and are either singleplayer games or multiplayer online games where players interact on a mediated basis. One reason for this can be seen in the nature of how computers are typically used-one user at a time and physically separated from other players. Handheld everyday devices like smartphones, on the other hand, break up these restrictions. AR can combine co-located, collaborative gaming, like it is associated with board games, with the processing power and the possibilities of real-time visual feedback known from digital games. The idea is to take the basic concept of a board game and use the device to source out tasks like checking rules, calculating scores and resources or apply chance based numbers. Apart from utilizing well established mechanics from digital games, new concepts and ideas can be introduced, since the combination of analogue and digital games is more as the sum of its parts.

Related Work

For mobile AR settings there are several interaction studies like gesture tracking or works related to traditional image and marker tracking (e.g. Peitz et al. [START_REF] Peitz | Wizard's Apprentice Gameplay-oriented Design of a Computer-augmented Board Game[END_REF]) or the recognition of finger movement via camera [START_REF] Hürst | Mobile Augmented Reality Interaction via Finger Tracking in a Board Game Setting[END_REF]. With all these new concepts being available, it is the main challenge for game designers to work with the technology and develop applicable games that use them extensively. There also have been studies regarding actual game piece tracking in order to maintain a certain physicality [START_REF] Molla | Augmented Reality for Board Games[END_REF]. A new medium will always take some time to explore its full potential, and work like Art of Defense by Duy-Nguyen et al. [START_REF] Nguyen | Art of defense: a Collaborative Handheld Augmented Reality Board game[END_REF] demonstrates how the use of tangible objects is a step in the right direction. As the team explicates in their paper about the game, tangible elements are a vital part in AR games in order to interact with the merged environments of reality and the virtual world. The Sphero [START_REF] Jones | Designing an Immersive and Entertaining Pervasive Gameplay Experience with Spheros as Game and Interface Elements[END_REF] is an AR installation that focuses on the physical environment around players and thus increases immersion and enjoyability. However, until now, apart from the technological advancements in the mobile AR game domain, little is known about the design approaches and procedures.

Our Game Design Approach: Vancouver Maneuver

Designing an AR board game contains practices from both design fields, since developers create games with the physical and social dimension of board games in mind, while simultaneously having the tools and experience of digital game development at their disposal. As a starting point for our game design approach we picked one specific form of game: the cooperative puzzle. While competitive games also have a strong social component they often tend to cause tactical avoidance of conversation and self-restraint. Since it is a common approach for board games we began with an analogue paper prototype which then got transferred into a digital one. Based on these findings we created our game prototype of Vancouver Maneuver (VM). Each player controls a burglar via his/her mobile device, working together to get a key and open a safe. Obstacles include security cameras, laser sensors and locked doors. By rotating rooms players solve different puzzles with increasing difficulty (see Figure 1). When thinking about board games and its differences in comparison to digital games, there are three interdependent factors to account for regarding game design: the general setting of players, the physicality of game pieces and the social interaction [START_REF] Andersen | Designing an Augmented Reality Board Game with Children: The Battleboard 3D Experience[END_REF]. Regarding the first factor the obvious design choice for VM was to position the two player opposite to one another to establish differing vantage points onto the game board in order to encourage social interaction. For example one player has vision over a certain area of the game world and has to describe it to his teammate. Apart from the physical vantage point AR can achieve this through different renderings on the respective players device. There are parts of the game world which are only visible to one player, regardless of his position, but rather linked to his avatar. This also helps to engage the players in real-world movement, an aspect that other AR games like BloxAR [8] also valued highly.

The second big aspect of board games is the physicality of game pieces and their interaction. In VM this factor is covered by separate board tiles for each rotatable room (see Figure 2). One thing to take account is the mobile device itself. Players tend to look through their virtual camera very often, so a secondary interaction with the other hand is not easy to manage -especially for new players. While interaction with real world objects is mandatory, it is still more reliable to fall back on well-known interaction methods players know from traditional video games. For example, an earlier prototype had single markers on the board to be pushed around like conventional pegs. While this added an additional layer of physical interaction, the flow of the game was much better when players controlled their avatar with pointing the cursor to the desired field on the grid. The third and most important part is the social interaction between players. For VM, cooperation is inherent regarding basic gameplay, since players get confronted with the same problems at the same time. Examples are the previously mentioned vantage points that require describing elements to a teammate or demanding switch puzzles. Moreover you have individual tasks to perform with your avatar while coordinating those with your teammate. The main challenge for collaborative play forms the solving of puzzles by observation and discussion.

It aims at a certain level of difficulty that is sufficient enough to force players to share information and argue over the best line of action [START_REF] Zagal | Collaborative Games: Lessons Learned from Board Games[END_REF].

Conclusion and Future Work

Mobile gaming is more prominent than ever, and with the current and future technology in smartphones there is a lot of potential regarding AR. While technical improvements are important, it is equally vital to catch up with the design side of this new medium. We have discussed that a hybrid approach between analogue board games and digital games opens up a research field on its own, since it is more than just a simple combination of two game types. VM addresses this issue and first play tests show that the approach is very promising. However, it is only the first step toward gathering knowledge regarding the creation and design of AR board games. The next steps will therefore be a refinement of the game design based on thorough formalized and controlled play testing. To take into account all social experiences and receptions of the game, we plan to set up different game sessions with both dedicated desktop and mobile AR versions of the game in order to compare traditional video gaming to the AR board game. Overall this work provides an illustration of our design experience and hopefully will serve as inspiration for other games of similar type to be developed.

Fig. 1 .

 1 Fig. 1. The board as seen through a mobile device (left) and the screen view (right).

Fig. 2 .

 2 Fig. 2. Diagram of different image trackers representing rooms.


Elisabeth Hackner
email: elisabeth.hackner@students.fh-hagenberg.atmichael.lankes@fh-hagenberg.at

Michael Lankes

Mindtraining: Playful Interaction Techniques for People with Dementia

Keywords: Serious games, dementia, Alzheimer's disease, tablet interaction, cognitive impairment, tablet activation

The paper presents the preliminary studies regarding applicable interaction techniques in the field of tablet games for dementia. Serious games in the dementia context are a well-researched topic. However, there is very little knowledge about performing gestures and interactions on tablet computers by users suffering from dementia. Since they already encounter many restrictions, a touch interface might be another obstacle. Tablet games often require a different kind of interaction, such as single tap, swipe, or drag and drop. We developed the Android application Mindtraining for dementia patients, which integrates multiple interaction techniques. The purpose of the tablet game is to facilitate an intuitive and efficient usage of gestures for people with early-and middle-stage dementia aged over 65 years. In our study we will investigate how people with dementia perform different gestures and how much help they need each time they use the application.

Introduction

The number of people with dementia, especially Alzheimer's disease (AD), is increasing and no cure has yet been found [START_REF]Alzheimer's Disease International: Global Knowledge, Dementia statistics[END_REF]. In addition to medicine-based therapies, also non-medicine-based therapies exist to slow down the progress of the disease. Current studies present a meaningful integration of tablet computers, such as iPads, into the therapy context with the aim of benefiting cognitive abilities or acting as trigger for the patient [START_REF] Mccallum | A Taxonomy of Serious Games for Dementia[END_REF][START_REF] Tom | Using Serious Games for Cognitive Disabilities[END_REF]. Particularly mobile games show great potential to stimulate dementia patients [START_REF]Aktivierung von Menschen mit Demenz im Pflegeheim[END_REF][START_REF] Kong | Conducting Cognitive Exercises for Early Dementia With the Use of Apps on iPads[END_REF]. An advantage of mobile technology is that the hardware is affordable and easy to handle as no external input control (such as a mouse or a keyboard) is needed. Studies often choose children games and educational games for evaluation in the dementia context [START_REF]Aktivierung von Menschen mit Demenz im Pflegeheim[END_REF][START_REF] Mccallum | A Taxonomy of Serious Games for Dementia[END_REF]. Although these types of games seem to be easy to use, they still often require too complex interactions or result in a cognitive overload for people with dementia. A major problem is that most technologies are not designed for people with cognitive disabilities and therefore making operating the device very hard to use.

Many dementia patients, especially people over an age of 65 years, also suffer from visual and/or hearing impairment due to their advanced age. However, mobile applications integrate assistive technologies very infrequently. These applications need to fulfill special requirements to ease the usage for people who are cognitively impaired. Basically, designing for dementia patients means moving back in time and thinking of events that happened in the past of one individual and the respective generation [START_REF]Aktivierung von Menschen mit Demenz im Pflegeheim[END_REF]. Metaphors, which are frequently used in mobile applications, have to tie in with the level of knowledge, the experiences and the cultural background of earlier years. Required gestures for touch displays have to be simple or alternatively be explained in a tutorial-like style. As dementia patients tend to have almost no short-term memory, they might need a tutorial with every time they use the application.

In this paper, we present preliminary findings of interaction techniques in the tablet game Mindtraining in terms of ease of use and how good dementia patients are able to remember different kinds of gestures. The application serves as an interactive playful photo album, which shows various content on each page and integrates multiple different gestures, such as tap, drag and drop, and swipe. As there seems to be an absence of best-practice approaches for interaction techniques on tablet devices we focus on a mixture of gestures in our application. Intuitive interaction techniques could support a more independent usage of applications on tablets. Caretakers would benefit from this, as they cannot afford the time to provide technical support and training for every single patient. Already a small amount of additional workload for nurses can be an obstacle for using a beneficial serious game in a nursing home.

Related Work

A dementia disease can affect multiple cognitive abilities, such as memory, attention, language, reasoning, judgment, reading, and writing [START_REF] Gogia | Clinical Alzheimer Rehabilitation[END_REF]. Recent research shows that video games with cognitive content have the potential of delaying the cognitive decline [START_REF]Aktivierung von Menschen mit Demenz im Pflegeheim[END_REF]. But only a few games were created for the target group dementia patients in mind, addressing their specific health restrictions.

In a research project, a mobile app was developed that offered personalized music based on the patient's life, with a special focus on usability [START_REF] Nezerwa | Alive Inside: Developing mobile apps for the cognitively impaired[END_REF]. Music and photos also played an important role in a pilot study, where tablets were used in dementia therapy for over three months [START_REF]Aktivierung von Menschen mit Demenz im Pflegeheim[END_REF]. In this study, they proposed listening and singing to music or watching photos (animals, patients themselves, family, children, babies, etc.) and videos as initiating and ending practice in therapy. This inspires communication and affects the patient's mood in a positive way. In the same study they mentioned that the caretaker had to give continuous positive feedback, especially at the end of the tablet therapy to motivate and encourage the patient. Games, which integrate continuous positive feedback and encouragement, would relieve the caretaker [START_REF]Aktivierung von Menschen mit Demenz im Pflegeheim[END_REF].

Software, especially games, for dementia is a well researched area and there are many recommendations available for developing dementia games [START_REF] Bouchard | Developing Serious Games Specifically Adapted to People Suffering from Alzheimer[END_REF][START_REF] Tom | Using Serious Games for Cognitive Disabilities[END_REF]. How-ever, there seems to be a lack of guidelines for interaction techniques -especially regarding touch interfaces. Senior people might not have any prior knowledge of operating touch devices. Hence, performing different gestures in an application might be already too complex for people with dementia. The developed prototypes in past research projects integrate different interaction techniques, either input with mouse and keyboard, WiiMote controller, touch or ecological gestures. In conclusion, all researchers of the prototypes tried to find a simple and natural way to interact with the respective system to reduce the cognitive overload for people with dementia. Either touch interaction or ecological gestures seemed to be the most successful interaction paradigms. These do not require any external controller, such as a mouse or keyboard. In a study with mobile games and elderly people, the participants reported that it is much easier to touch the objects on the screen than using a mouse [START_REF] Cota | Niltom: Mobile game design for the elderly: A study with focus on the motivation to play[END_REF]. Learning how to interact with a software system is a complex task, in particular for users, who never used computer systems before. Yet, studies have shown that elderly people with dementia are willing to learn new technologies [START_REF] Lauriks | Review of ICT-based services for identified unmet needs in people with dementia[END_REF][START_REF] Lim | Usability of Tablet Computers by People with Early-Stage Dementia[END_REF]. In another study with dementia patients, half of the participants had never used a mobile device before. However, all of them indicated that they would like to see more technology and believed they could benefit from it [START_REF] Kong | Conducting Cognitive Exercises for Early Dementia With the Use of Apps on iPads[END_REF]. Moreover tablets cover many positive features like high-quality responsiveness multi-touch screen, mobility, accessibility and ease of aquition [START_REF] Tom | Using Serious Games for Cognitive Disabilities[END_REF].

Game Prototype Mindtraining

Based on related work, we established the requirements for Mindtraining and extended the application with different interaction techniques. The requirements include: (1) providing visual and auditory help; (2) matching the mental model with the conceptional model; (3) giving motivational messages and positive feedback when achieving a goal or making a mistake; (4) providing short and simple messages; and (5) counteracting the declining cognitive abilities of the persona [START_REF] Bouchard | Developing Serious Games Specifically Adapted to People Suffering from Alzheimer[END_REF][START_REF]Aktivierung von Menschen mit Demenz im Pflegeheim[END_REF][START_REF] Lim | Usability of Tablet Computers by People with Early-Stage Dementia[END_REF]. Mindtraining is an interactive photo album with a playful integration of cognitive games. A photo album is an item, which is also known from the earlier years of nowadays dementia patients, hence it should present a good mental model for the players. Visual aids, especially photos, can stimulate the memories and are therefore a proofed concept in dementia therapy [START_REF]Aktivierung von Menschen mit Demenz im Pflegeheim[END_REF]. Playing the game requires different gestures and interaction techniques. In the album you have to swipe through the pages, tap on photos to see them in full screen and use tap for turning on and off a music radio. The radio plays songs of the earlier years of the patients and should serve as alternate stimulation of the user. Also a cognitive game with completing of sayings is implemented on multiple pages with two different scenarios: (1) tapping on the right answer, [START_REF] Mccallum | A Taxonomy of Serious Games for Dementia[END_REF] dragging the right answer to a target location. Wordplays, including sayings, are widely used in mind training therapies for dementia patients to exercise their mind.

The system is complemented with a logging module which tracks the interaction of the user and logs the data in JSON format to files on the device. The module logs single tap, double tap, long press, swipe from left to right and vice versa, swipe from top to bottom and vice versa and dragging interactions of draggable elements. The logging is applied to the following view types of Android: TextView, Image, Button, ImageView and ImageButton.

Our objective is to investigate how people with dementia cope with different gestures in a mobile playful application. On the one hand it is interesting how good people can remember gestures and how intuitive they are. On the other hand we want to find out if one of the gestures might be easier to perform than another one and give recommendations of applying gestures in a mobile application.

Preliminary Study

The application was tested by eight participants, see Fig. 1 (age: 56-90, gender: 3 male, 5 female). Three of the participants have early-stage dementia, one has middle-stage dementia, the others don't have dementia. The results of these tests were used to optimize the application and eradicate remaining usability problems of Mindtraining. The device used is a 10.1" sized ASUS MeMO Pad 10 Android tablet. A protection case covers the back of the device, which firstly gives additional grip and secondly provides a stable base to position it on a table in the right angle. In total, four main iterations, each included planning, implementing, testing and evaluation, took place. Besides adapting sizes for fonts and graphics, two important issues were optimized during these iterations. At first people were instructed which gestures had to be performed, such as tapping on a photo or swiping for flipping a page. When it came to dementia patients, switching between the different gestures caused problems. As they had learned that swiping from right to left resulted in the intended outcome, they also tried swiping on photos and buttons. To solve the cognitive overload of switching between different gestures, simple animations for tapping and swiping were implemented at the desired positions to provide a visual instruction how to perform the gesture on the element. This optimization showed that dementia patients needed fewer instructions from the caretaker on how to interact with the different elements.

The second main usability problem, which had been observed, is that a single tap is often difficult to perform by elderly people including dementia patients. The main issues are sideslipping of the finger and the duration of the tap. Also the user sometimes touches the screen with the fingernails, which has no effect on a capacitive display. With Android's standard functionality of clickable elements the action is only executed when performing a single tap on the element. To solve this issue we extended Android's standard functionality for clickable elements in a way that these elements also react to gestures, such as swipe, double tap and long press. The logging module tracks, which gesture has been performed on an element. This will allow an analysis of the usage of gestures afterwards. Due to the single tap problem, the scenario with dragging the right answer to a target location in the sayings game, could be performed much faster and more fluently than single tapping on the right answer.

As next step, a field test with three participants with early-stage dementia with 75-90 years in age, will be conducted to observe the interactions. The test will take place in a small day-care facility where dementia patients get cared for three times a week. To examine which gestures on a tablet device are best suited for this target group, we integrated an automatic logging module in the final prototype. The logging module tracks how a user interacts with visible elements on the screen. Additional to the logging module, an observation protocol will serve as a documentation of qualitative data during the field test.

Conclusion and Future Work

In this paper we presented the purpose of serious games in the dementia context and introduced Mindtraining, an Android application that facilitates an intuitive usage of gestures. Software design guidelines for people with dementia are a common topic in research, but there seems to be a lack of recommendations when it comes to touch devices and their interaction techniques. In our application we are tracking and observing the user's interaction with the tablet to find out which gestures can be performed better than others. The next step will be conducting a field test with dementia patients and analysing the used interactions in the application Mindtraining.

Fig. 1 .

 1 Fig. 1. Typical setting of the the field tests: Subject playing the game, a carer sitting next to her and supporting her when questions arise and the observer in the background, taking notes.