It Takes Two To Tango: Conflicts Between Users on the Reality-Virtuality Continuum and Their Bystanders Jonas Auda Uwe Gruenefeld Sven Mayer University of Duisburg-Essen University of Duisburg-Essen LMU Munich Essen, Germany Essen, Germany Munich, Germany jonas.auda@uni-due.de uwe.gruenefeld@uni-due.de sven.mayer@i.lmu.de ABSTRACT entering person starts a conversation (cause), which slightly aects Over the last years, Augmented and Virtual Reality technology be- the VR user’s immersion and transports the user away from their came more immersive. However, when users immerse themselves virtual environment (eect). is example shows an interaction in these digital realities, they detach from their real-world environ- across multiple realities with some adverse side-eects on immer- ments. This detachment creates conicts that are problematic in sion. In general, the caused eects can be positive and intentional, public spaces such as planes but also private settings. Consequently, but in many situations in which these eects are not considered on the one hand, the detaching from the world creates an immerse and the challenges that come along remain unaddressed, they can experience for the user, and on the other hand, this creates a social induce negative side-eects, limiting users’ experiences. Here, both, conict with bystanders. With this work, we highlight and catego- user and bystander, need to be considered to guarantee a good user rize social conicts caused by using immersive digital realities. We experience. To reect this, we titled our work“it takes two to tango.” rst present dierent social seings in which social conicts arise and then provide an overview of investigated scenarios. Finally, we 2 INTRODUCTION present research opportunities that help to address social conicts In the past few years, there has been great progress in the areas between immersed users and bystanders. of AR and VR. In particular, technological developments and the availability of head-mounted displays (HMDs) for end-users have CCS CONCEPTS made great strides. This enables users both at home and on the go • Human-centered computing  Mixed / augmented reality; Vir- to superimpose digital information in the form of graphic represen- tual reality. tations over the world or even to immerse themselves completely in virtual realities. Over the past years, technical availability has made KEYWORDS it possible for researchers to understand, for the rst time, how Reality-Virtuality Continuum, Augmented Reality, Virtual Reality, people can use AR and VR. The main focus here was on how users Transitional Interfaces, Bystander can better interact with digital information and how information can be better presented to create a better user experience (UX) and Reference Format: Jonas Auda, Uwe Gruenefeld, and Sven Mayer. 2020. It Takes Two To Tango: better immersion. Conf icts Between Users on the Reality-Virtuality Continuum and Their The various realities such as AR, augmented virtuality (AV), Bystanders. In Cross-Reality (XR) Interaction, ACM ISS 2020 (International and VR can be mapped on a continuum – the reality-virtuality Workshop on XR Interaction 2020). continuum [28]. Many applications currently use a specic area on the continuum called a manifestation. For example, training 1 WHAT IS CROSS-REALITY INTERACTION? in VR [9, 14, 20], extended environments/workplaces with AR [ 2, We interpret cross-reality interaction as a cause-eect relation- 10, 21], and the collaboration of several people in AV [ 4, 26, 29]. ship that involves at least two dierent manifestations of the real- However, the continuum is a smooth continuance between two ity–virtuality continuum [28], whereas a manifestation represents extremes, reality and virtuality, that allows endless congurations. an experience located at a concrete area on the continuum. In other mixed reality (MR) expresses everything that is not completely left words, an event happening in one reality causes an eect that im- (reality) or right (virtuality) on the continuum. Improving the UX pacts another form of reality, e.g., augmented reality (AR) or virtual for users present in dierent realities has been the great goal of the reality (VR). In this paper, we limit ourselves to cross-reality in- last few years. teractions in which users are co-located, and their presence in the Clearly, the real world never stops surrounding the user and same physical space induces specic challenges that need to be moves at its own pace. People around the user could inuence the considered. For example, a person enters a room where another user’s experience in a virtually enhanced or purely virtual environ- person enjoys a virtual environment with a VR headset. Then, the ment [26]. Additionally, physical structures from the real world can also inuence the user [26] or even incoming digital information Copyright © 2020 for this paper by its authors. Use permied under Creative in the form of notications [ 11, 13, 35, 41]. Understanding these Commons License Aribution 4.0 International (CC BY 4.0). Cross-Reality (XR) Interaction, ACM ISS 2020, November 8 2020, Lisbon, Portugal experiences made by the user will become even more important in the coming years and will increasingly crystallize into a new research direction. Today, the question arises of how the real world can be appro- priately integrated into alternative realities to raise the feeling of International Workshop on XR Interaction 2020, November 8 2020, Lisbon, Portugal Auda, et al. immersion for the user on the one hand, but on the other hand, well [8]. To understand potential con�icts between users manifest- not to lose complete contact with the outside world. Today there ing somewhere on the reality-virtuality continuum and the people are �rst attempts to explore how persons around the user can around them, we analyzed and categorized related work into three be directly integrated into the interaction or even enable a con- groups: private, semi-private (e.g. school/work), and public. In the versation between di�erent realities [26]. It is often best to shift following, we present the three di�erent settings of use and their manifestation of bystanders and artifacts over time on the reality- di�erent user expectations and norms. virtuality continuum to make an interaction possible [26]. That means either shifting the user towards the real world or bringing 4.1 Private the bystanders into an alternate reality. In the simplest case, the Mostly for entertainment purposes, users experience digital real- VR user would drop their VR HMD and thus would be completely ities in private settings. The number of bystanders is relatively abandon the alternative reality, which would make a conversation low, and users and their activities are known to the bystanders. An possible, but also completely destroys the immersion. Alternatively, example is a group of friends that takes turns on a VR headset. For the bystander could put on an HMD and dive into the VR, which the additional involvement of bystanders in these gaming activi- would also enable interaction, but here comes the problem that the ties, di�erent collaborative games exist [7]. Nevertheless, private bystander also loses contact with the real world. Consequently, it settings are not limited to indoor but extend to other locations as becomes clear that the two simple solutions are not good solutions well. For example, users can experience VR while being in a driving and that a good solution lies between the two extremes. car [16, 27, 30]. Therefore, the focus should be on the technical realization of alternative realities, as seen up to now, and on the social component of disconnecting the user [38]. This is a main challenge that needs to 4.2 Semi-Private - Work/School be addressed in the future. The �rst signs that isolating oneself from In work or school environments, users and bystanders likely know the real world by immersing oneself in an alternative world is caus- each other as they are mostly access controlled so that only au- ing social challenges that can already be seen in planes and trains thorized people can enter and visitors often stand out (e.g. visitor [39], for instance, social norms for intractability are not clear [12]. badge). Thus, the users’ experience is not necessarily of interest for An example is the use of noise-canceling headphones. Although bystanders and the hurdle to engage in an interaction lower due to such headphones only overwrite the user’s auditory perception, the connection they share by being allowed in the space. Moreover, this causes problems, especially at the beginning of conversations education often requires collaboration between subjects [25, 31]. [19]. Also, alternative realities are usually �xated on the visual per- ception of humans. This highlights the problem of social isolation 4.3 Public since visual perception is dominant over other senses [33]. In recent years, public settings became more relevant as a social In the following, we �rst discuss di�erent social settings in which setting for experiencing digital realities. Compared to private or the use of alternative realities have been envisioned. In detail, we semi-private settings, users and bystanders likely do not know each discuss the di�erent characteristics from which we, in a second step, other. In detail, we can divide the settings in public (e.g. streets, and derive three di�erent relationships between users and bystanders. parks) and semi-public setting (e.g., co�eehouses, and shops). Usage of, for example, VR in public spaces can result in the unperceived 3 METHODOLOGY presence of others or a less immersive experience due to external To derive the di�erent classes of social settings and correspond- interruptions [22, 24]. Nevertheless, using VR in public spaces can ing characteristics, we crawled relevant literature using Google have various use cases, such as improving the travel experience Scholar and focused on two online libraries in particular (ACM during long �ights [37, 39]. Digital Library and IEEE Xplore), considering work published in the last �ve years in topic-related conferences (CHI, UIST, VRST, 5 RESEARCH SCENARIOS IEEE VR, IEEE ISMAR). To �nd relevant papers, we searched for one In previous work, di�erent scenarios that involve users on the of the following keywords and their abbreviations in title or ab- reality-virtuality continuum and their bystanders have been inves- stract: “Mixed Reality,” “Augmented Reality,” “Virtual Reality,” and tigated. When studying these scenarios, it becomes visible that often “Reality-Virtuality Continuum.” We collected all relevant papers in a the relationship between users and their bystander di�ers. Here, re- spreadsheet and iteratively added information dimensions classify- lationship refers to the relative position of users and bystanders on ing the publications. For this paper, we identi�ed di�erent contexts the continuum. In the following, we grouped the research scenarios of users and their interaction between them. In the following, we from previous work based on the described relationship between introduce these settings and scenarios in more detail. users and bystanders (see Figure 1). 4 SOCIAL SETTINGS 5.1 Isolated Experiences Users can experience digital realities in di�erent social settings. Isolated experiences exploit the circumstances that users detach While VR often is experienced for entertainment purposes in pri- from their real-world environments. While this seems to contradict vate settings alone or with friends, the technology becomes more our work’s motivation, it still can make sense in certain situations. relevant for professional contexts. Furthermore, previous research For example, in a noisy o�ce environment with lots of visual ele- suggests that public settings can become relevant in the future as ments causing distraction from work, a virtual environment may It Takes Two To Tango International Workshop on XR Interaction 2020, November 8 2020, Lisbon, Portugal Mixed Reality (MR) Reality Virtuality Bystander User User is somewhere on the continuum Isolated Experiences far away, no transition Bystander Inclusion uni-directional transition Collaboration bi-directional transition Figure 1: Groups of scenarios that share the same relationship between users on the continuum and their bystanders. be a good idea to isolate from these negative in�uences [34]. An- 6 RESEARCH OPPORTUNITIES other example is a situation in which multiple VR users share the In the following, we highlight future research opportunities derived same space but not the same virtual experience [3], or a situation from the introduced social settings and classes of relationships in which bystanders cross the playing area of a user[40]. These between users and their bystanders. examples have in common that both bystanders and users do not have an interest in one another. Hence, the larger the relative dis- Expanding to Public and Work Places. First-generation VR and tance between them on the continuum, the better is the overall AR devices are designed for single-user experiences in private con- experience. texts. However, designing devices that foster interaction between users and bystanders can facilitate communication and interplay 5.2 Bystander Inclusion in various contexts. In many situations, users manifesting on certain spots on the reality- virtuality continuum would like to include bystanders in their ex- Transitional Experiences. New technology might allow easy tran- perience, or bystanders would like to participate in the user’s expe- sitions along the continuum (e.g. video see-through HMDs). De- rience. Here, users’ experience on the continuum is at focus, and pending on the scenario, it makes sense to create experiences that, bystanders get included in various ways. For example, bystanders for example, allow the user to transit from reality into VR gradually. want to see what a user in VR experiences, and therefore, previ- Thereby users and bystanders can interact on di�erent levels de- ous work suggests using a CAVE [17, 18] or display attached to pending on how far they must transit into the reality of each other. the HMD [23, 32]. Another example is to have bystanders enrich Based on the bene�ts it provides, we expect transitional interfaces the experience by giving di�erent forms of haptic feedback [5, 6]. to become more relevant in the future. These examples share that bystanders transition on the continuum towards the user, while the user does not transit. The goal is to Visualization Helps Understanding. Researchers and developers keep the user immersed but to empower bystanders to participate might face challenges while investigating or developing MR sce- in the experience. narios and therefore need insights into the sessions of their users. Tools and Frameworks that help us describe or analyze these sce- 5.3 Collaboration narios [1]. Ways to stronger considerate di�erent social settings (public, work, and private) in research might be key to understand With collaboration, we refer to scenarios that involve achieving a the interplay of involved users, objects, and environments. shared goal. Compared to bystander inclusion, this means that both users and bystanders alter their experience and come closer to each other on the continuum, see Figure 1. An example would be a by- 7 CONCLUSION stander and user playing a game together where the bystander can In this paper, we present di�erent scenarios for the use of alterna- help the user reach their objective (e.g., to solve a maze puzzle [36]) tive realities. By categorizing them, we found three di�erent social or where both play against each other (e.g., in a sword �ght [15]). contexts: private, work, and public in which alternative realities In the latter scenario, we stretched the term collaboration a bit; can be used. From these, we derive characteristics of di�erent re- however, we argue that both users still share a goal – having fun lationships between the user and bystanders. Here, we argue that together. In sum, we understand this last class of user-bystander three types of interactions are important to explore in the future to relationships as scenarios in which both experiences are altered to enable easy switching between manifestations as this ultimately perceive each other’s presence. allows for a satisfying user-bystander interaction. International Workshop on XR Interaction 2020, November 8 2020, Lisbon, Portugal Auda, et al. REFERENCES Computing Systems (Denver, Colorado, USA) (CHI ’17). Association for Computing [1] Shivam Agarwal, Jonas Auda, Stefan Schneegaß, and Fabian Beck. 2020. A Design Machinery, New York, NY, USA, 4021–4033. https://doi.org/10.1145/3025453. and Application Space for Visualizing User Sessions of Virtual and Mixed Reality 3025683 Environments. In Vision, Modeling, and Visualization, Jens Krüger, Matthias [16] Philipp Hock, Sebastian Benedikter, Jan Gugenheimer, and Enrico Rukzio. 2017. Niessner, and Jörg Stückler (Eds.). The Eurographics Association. https://doi. CarVR: Enabling In-Car Virtual Reality Entertainment. In Proceedings of the 2017 org/10.2312/vmv.20201194 CHI Conference on Human Factors in Computing Systems (Denver, Colorado, USA) [2] Karan Ahuja, Sujeath Pareddy, Robert Xiao, Mayank Goel, and Chris Harri- (CHI ’17). Association for Computing Machinery, New York, NY, USA, 4034–4044. son. 2019. LightAnchors: Appropriating Point Lights for Spatially-Anchored https://doi.org/10.1145/3025453.3025665 Augmented Reality Interfaces. In Proceedings of the 32nd Annual ACM Sym- [17] Akira Ishii, Masaya Tsuruta, Ippei Suzuki, Shuta Nakamae, Tatsuya Minagawa, posium on User Interface Software and Technology (New Orleans, LA, USA) Junichi Suzuki, and Yoichi Ochiai. 2017. ReverseCAVE: Providing Reverse Perspec- (UIST ’19). Association for Computing Machinery, New York, NY, USA, 189–196. tives for Sharing VR Experience. In ACM SIGGRAPH 2017 Posters (Los Angeles, https://doi.org/10.1145/3332165.3347884 California) (SIGGRAPH ’17). Association for Computing Machinery, New York, [3] Mahdi Azmandian, Timofey Grechkin, and Evan S. Rosenberg. 2017. An evalua- NY, USA, Article 28, 2 pages. https://doi.org/10.1145/3102163.3102208 tion of strategies for two-user redirected walking in shared physical spaces. In [18] Akira Ishii, Masaya Tsuruta, Ippei Suzuki, Shuta Nakamae, Junichi Suzuki, and 2017 IEEE Virtual Reality (VR ’17). 91–98. https://doi.org/10.1109/VR.2017.7892235 Yoichi Ochiai. 2019. Let Your World Open: CAVE-Based Visualization Methods of [4] Gerd Bruder, Frank Steinicke, Kai Rothaus, and Klaus Hinrichs. 2009. Enhancing Public Virtual Reality towards a Shareable VR Experience. In Proceedings of the Presence in Head-Mounted Display Environments by Visual Body Feedback 10th Augmented Human International Conference 2019 (Reims, France) (AH2019). Using Head-Mounted Cameras. In 2009 International Conference on CyberWorlds. Association for Computing Machinery, New York, NY, USA, Article 33, 8 pages. 43–50. https://doi.org/10.1109/CW.2009.39 https://doi.org/10.1145/3311823.3311860 [5] Lung-Pan Cheng, Patrick Lühne, Pedro Lopes, Christoph Sterz, and Patrick Baud- [19] Francisco Kiss, Sven Mayer, and Valentin Schwind. 2020. Audio VR: Did Video isch. 2014. Haptic Turk: A Motion Platform Based on People. In Proceedings of the Kill the Radio Star? Interactions 27, 3 (April 2020), 46–51. https://doi.org/10. SIGCHI Conference on Human Factors in Computing Systems (Toronto, Ontario, 1145/3386385 Canada) (CHI ’14). Association for Computing Machinery, New York, NY, USA, [20] Changyang Li, Wei Liang, Chris Quigley, Yibiao Zhao, and Lap-Fai Yu. 2017. 3463–3472. https://doi.org/10.1145/2556288.2557101 Earthquake Safety Training through Virtual Drills. IEEE Transactions on Visual- [6] Lung-Pan Cheng, Thijs Roumen, Hannes Rantzsch, Sven Köhler, Patrick Schmidt, ization and Computer Graphics 23, 4 (2017), 1275–1284. https://doi.org/10.1109/ Robert Kovacs, Johannes Jasper, Jonas Kemper, and Patrick Baudisch. 2015. TVCG.2017.2656958 TurkDeck: Physical Virtual Reality Based on People. In Proceedings of the 28th [21] Hanchuan Li, Eric Whitmire, Alex Mariakakis, Victor Chan, Alanson P Sample, Annual ACM Symposium on User Interface Software & Technology (Charlotte, NC, and Shwetak N Patel. 2019. IDCam: Precise Item Identi�cation for AR Enhanced USA) (UIST ’15). Association for Computing Machinery, New York, NY, USA, Object Interactions. In 2019 IEEE International Conference on RFID (RFID ’19). 1–7. 417–426. https://doi.org/10.1145/2807442.2807463 https://doi.org/10.1109/RFID.2019.8719279 [7] Arindam Dey, Thammathip Piumsomboon, Youngho Lee, and Mark Billinghurst. [22] Christian Mai and Mohamed Khamis. 2018. Public HMDs: Modeling and Under- 2017. E�ects of Sharing Physiological States of Players in a Collaborative Virtual standing User Behavior around Public Head-Mounted Displays. In Proceedings of Reality Gameplay. In Proceedings of the 2017 CHI Conference on Human Factors in the 7th ACM International Symposium on Pervasive Displays (Munich, Germany) Computing Systems (Denver, Colorado, USA) (CHI ’17). Association for Computing (PerDis ’18). Association for Computing Machinery, New York, NY, USA, Article Machinery, New York, NY, USA, 4045–4056. https://doi.org/10.1145/3025453. 21, 9 pages. https://doi.org/10.1145/3205873.3205879 3026028 [23] Christian Mai, Lukas Rambold, and Mohamed Khamis. 2017. TransparentHMD: [8] Pouya Eghbali, Kaisa Väänänen, and Tero Jokela. 2019. Social Acceptability of Revealing the HMD User’s Face to Bystanders. In Proceedings of the 16th Inter- Virtual Reality in Public Spaces: Experiential Factors and Design Recommenda- national Conference on Mobile and Ubiquitous Multimedia (Stuttgart, Germany) tions. In Proceedings of the 18th International Conference on Mobile and Ubiquitous (MUM ’17). Association for Computing Machinery, New York, NY, USA, 515–520. Multimedia (Pisa, Italy) (MUM ’19). Association for Computing Machinery, New https://doi.org/10.1145/3152832.3157813 York, NY, USA, Article 28, 11 pages. https://doi.org/10.1145/3365610.3365647 [24] Christian Mai, Tim Wiltzius, Florian Alt, and Heinrich Hußmann. 2018. Feeling [9] Markus Funk, Mareike Kritzler, and Florian Michahelles. 2017. HoloCollab: A Alone in Public: Investigating the In�uence of Spatial Layout on Users’ VR Shared Virtual Platform for Physical Assembly Training Using Spatially-Aware Experience. In Proceedings of the 10th Nordic Conference on Human-Computer Head-Mounted Displays. In Proceedings of the Seventh International Conference Interaction (Oslo, Norway) (NordiCHI ’18). Association for Computing Machinery, on the Internet of Things (Linz, Austria) (IoT ’17). Association for Computing New York, NY, USA, 286–298. https://doi.org/10.1145/3240167.3240200 Machinery, New York, NY, USA, Article 19, 7 pages. https://doi.org/10.1145/ [25] Stefan Marks and David White. 2020. Multi-Device Collaboration in Virtual 3131542.3131559 Environments. In Proceedings of the 2020 4th International Conference on Virtual [10] Markus Funk, Sven Mayer, and Albrecht Schmidt. 2015. Using In-Situ Projection and Augmented Reality Simulations (Sydney, NSW, Australia) (ICVARS 2020). to Support Cognitively Impaired Workers at the Workplace. In Proceedings of Association for Computing Machinery, New York, NY, USA, 35–38. https://doi. the 17th International ACM SIGACCESS Conference on Computers & Accessibility org/10.1145/3385378.3385381 (Lisbon, Portugal) (ASSETS ’15). Association for Computing Machinery, New [26] Mark McGill, Daniel Boland, Roderick Murray-Smith, and Stephen Brewster. York, NY, USA, 185–192. https://doi.org/10.1145/2700648.2809853 2015. A Dose of Reality: Overcoming Usability Challenges in VR Head-Mounted [11] Ceenu George, Manuel Demmler, and Heinrich Hussmann. 2018. Intelligent Displays. In Proceedings of the 33rd Annual ACM Conference on Human Factors in Interruptions for IVR: Investigating the Interplay between Presence, Workload Computing Systems (Seoul, Republic of Korea) (CHI ’15). Association for Comput- and Attention. In Extended Abstracts of the 2018 CHI Conference on Human Factors ing Machinery, New York, NY, USA, 2143–2152. https://doi.org/10.1145/2702123. in Computing Systems (Montreal QC, Canada) (CHI EA ’18). Association for 2702382 Computing Machinery, New York, NY, USA, 1–6. https://doi.org/10.1145/3170427. [27] Mark McGill, Alexander Ng, and Stephen Brewster. 2017. I Am The Passenger: 3188686 How Visual Motion Cues Can In�uence Sickness For In-Car VR. In Proceedings [12] Ceenu George, Philipp Janssen, David Heuss, and Florian Alt. 2019. Should I of the 2017 CHI Conference on Human Factors in Computing Systems (Denver, Interrupt or Not? Understanding Interruptions in Head-Mounted Display Settings. Colorado, USA) (CHI ’17). Association for Computing Machinery, New York, NY, In Proceedings of the 2019 on Designing Interactive Systems Conference (San Diego, USA, 5655–5668. https://doi.org/10.1145/3025453.3026046 CA, USA) (DIS ’19). Association for Computing Machinery, New York, NY, USA, [28] Paul Milgram and Fumio Kishino. 1994. A taxonomy of mixed reality visual 497–510. https://doi.org/10.1145/3322276.3322363 displays. IEICE TRANSACTIONS on Information and Systems 77, 12 (1994), 1321– [13] Sarthak Ghosh, Lauren Winston, Nishant Panchal, Philippe Kimura-Thollander, 1329. Je� Hotnog, Douglas Cheong, Gabriel Reyes, and Gregory D. Abowd. 2018. [29] David Nahon, Geo�rey Subileau, and Benjamin Capel. 2015. “Never Blind VR” Noti�VR: Exploring Interruptions and Noti�cations in Virtual Reality. IEEE enhancing the virtual reality headset experience with augmented virtuality. In Transactions on Visualization and Computer Graphics 24, 4 (2018), 1447–1456. 2015 IEEE Virtual Reality (VR ’15). 347–348. https://doi.org/10.1109/VR.2015. https://doi.org/10.1109/TVCG.2018.2793698 7223438 [14] Scott W Greenwald, Wiley Corning, Gavin McDowell, Pattie Maes, and John [30] Pablo E. Paredes, Stephanie Balters, Kyle Qian, Elizabeth L. Murnane, Francisco Belcher. 2019. ElectroVR: An Electrostatic Playground for Collaborative, Ordóñez, Wendy Ju, and James A. Landay. 2018. Driving with the Fishes: Towards Simulation-Based Exploratory Learning in Immersive Virtual Reality. In Pro- Calming and Mindful Virtual Reality Experiences for the Car. Proc. ACM Interact. ceedings of the 13th International Conference on Computer Supported Collabora- Mob. Wearable Ubiquitous Technol. 2, 4, Article 184 (Dec. 2018), 21 pages. https: tive Learning (CSCL ’19). International Society of the Learning Sciences (ISLS). //doi.org/10.1145/3287062 https://repository.isls.org//handle/1/1761 [31] Krzysztof Pietroszek and Chao Cheng Lin. 2019. UniVResity: Face-to-Face Class [15] Jan Gugenheimer, Evgeny Stemasov, Julian Frommel, and Enrico Rukzio. 2017. Participation for Remote Students Using Virtual Reality. In 25th ACM Symposium ShareVR: Enabling Co-Located Experiences for Virtual Reality between HMD and on Virtual Reality Software and Technology (Parramatta, NSW, Australia) (VRST Non-HMD Users. In Proceedings of the 2017 CHI Conference on Human Factors in ’19). Association for Computing Machinery, New York, NY, USA, Article 97, 2 pages. https://doi.org/10.1145/3359996.3364730 It Takes Two To Tango International Workshop on XR Interaction 2020, November 8 2020, Lisbon, Portugal [32] Daniel Pohl and Carlos F. de Tejada Quemada. 2016. See what I see: Concepts and 3D User Interfaces Abstracts and Workshops (VRW ’20). 279–280. https: to improve the social acceptance of HMDs. In 2016 IEEE Virtual Reality (VR ’16). //doi.org/10.1109/VRW50115.2020.00058 267–268. https://doi.org/10.1109/VR.2016.7504756 [38] Valentin Schwind, Jens Reinhardt, Rufat Rzayev, Niels Henze, and Katrin Wolf. [33] Michael I Posner, Mary J Nissen, and Raymond M Klein. 1976. Visual dominance: 2018. Virtual reality on the go?: a study on social acceptance of VR glasses. In an information-processing account of its origins and signi�cance. Psychological Proceedings of the 20th International Conference on Human-Computer Interaction review 83, 2 (1976), 157. https://doi.org/10.1037/0033-295X.83.2.157 with Mobile Devices and Services Adjunct - MobileHCI ’18. ACM Press, Barcelona, [34] Anastasia Ruvimova, Junhyeok Kim, Thomas Fritz, Mark Hancock, and David C. Spain, 111–118. https://doi.org/10.1145/3236112.3236127 Shepherd. 2020. "Transport Me Away": Fostering Flow in Open O�ces through [39] Julie R. Williamson, Mark McGill, and Khari Outram. 2019. PlaneVR: Social Virtual Reality. In Proceedings of the 2020 CHI Conference on Human Factors in Acceptability of Virtual Reality for Aeroplane Passengers. In Proceedings of the Computing Systems (Honolulu, HI, USA) (CHI ’20). Association for Computing 2019 CHI Conference on Human Factors in Computing Systems (Glasgow, Scotland Machinery, New York, NY, USA, 1–14. https://doi.org/10.1145/3313831.3376724 Uk) (CHI ’19). Association for Computing Machinery, New York, NY, USA, 1–14. [35] Rufat Rzayev, Sven Mayer, Christian Krauter, and Niels Henze. 2019. Noti�cation https://doi.org/10.1145/3290605.3300310 in VR: The E�ect of Noti�cation Placement, Task and Environment. In Proceedings [40] Keng-Ta Yang, Chiu-Hsuan Wang, and Liwei Chan. 2018. ShareSpace: Facilitating of the Annual Symposium on Computer-Human Interaction in Play (Barcelona, Shared Use of the Physical Space by Both VR Head-Mounted Display and External Spain) (CHI PLAY ’19). Association for Computing Machinery, New York, NY, Users. In Proceedings of the 31st Annual ACM Symposium on User Interface Software USA, 199–211. https://doi.org/10.1145/3311350.3347190 and Technology (Berlin, Germany) (UIST ’18). Association for Computing Machin- [36] Pejman Sajjadi, Edgar Omar Cebolledo Gutierrez, Sandra Trullemans, and Olga ery, New York, NY, USA, 499–509. https://doi.org/10.1145/3242587.3242630 De Troyer. 2014. Maze Commander: A Collaborative Asynchronous Game Using [41] André Zenner, Marco Speicher, Sören Klingner, Donald Degraen, Florian Daiber, the Oculus Rift & the Sifteo Cubes. In Proceedings of the First ACM SIGCHI Annual and Antonio Krüger. 2018. Immersive Noti�cation Framework: Adaptive & Symposium on Computer-Human Interaction in Play (Toronto, Ontario, Canada) Plausible Noti�cations in Virtual Reality. In Extended Abstracts of the 2018 CHI (CHI PLAY ’14). Association for Computing Machinery, New York, NY, USA, Conference on Human Factors in Computing Systems (Montreal QC, Canada) 227–236. https://doi.org/10.1145/2658537.2658690 (CHI EA ’18). Association for Computing Machinery, New York, NY, USA, 1–6. [37] Thereza Schmelter and Kristian Hildebrand. 2020. Analysis of Interaction Spaces https://doi.org/10.1145/3170427.3188505 for VR in Public Transport Systems. In 2020 IEEE Conference on Virtual Reality