Background: Many researchers have been evaluating how digital media may impact the emotional and ... more Background: Many researchers have been evaluating how digital media may impact the emotional and perspective taking aspects of empathy in both clinical and nonclinical settings. Despite the growing interest in using virtual reality (VR) and VR games to motivate empathy, few studies have focused on empathy for people who live with chronic pain. Objective: Chronic pain affects, by conservative estimates, 1 in 5 people in industrialized countries. Despite this prevalence, public awareness of chronic pain was remarkably low until the recent opioid crisis; as a result, stigma remains a problem frequently faced by people who live with this condition. To address this, the VR game AS IF was developed to increase nonpatients' empathy toward the growing number of people who live with long-term chronic pain. On the basis of our prior work, we overhauled our approach, designed and built a VR prototype and evaluated it, and offered design suggestions for future research. Methods: We introduced the design features of the VR game AS IF and described the study we devised to evaluate its effectiveness. We adopted a mixed methods approach and compared the empathy-related outcomes in both pre-and posttesting. A total of 19 participants were recruited. Results: The findings of this study suggest that the VR game was effective in improving implicit and explicit empathy as well as its emotional and perspective taking aspects. More specifically, for the Empathy Scale, the total pretest scores (mean 47.33, SD 4.24) and posttest scores (mean 59.22, SD 4.33) did not reach statistical significance (P=.08). However, we did find differences in the subscales. The kindness subscale showed a statistically significant increase in the posttest score (mean 15.61, SD 2.85) compared with the pretest score (mean 17.06, SD 2.65;P=.001). For the Willingness to Help Scale, a significant increase was observed from a t test analysis (P<.001) of scores before (mean 7.17, SD 2.28) and after (mean 8.33, SD 2.03) the gameplay. The effect size for this analysis was large (d=−1.063). Conclusions: The contributions of this research are as follows: AS IF provides a promising approach for designing VR games to motivate people's empathy toward patients with chronic pain, the study evaluates the potential effectiveness of such a VR approach, and the general design suggestions devised from this study could shed light on future VR game systems.
Communications in computer and information science, 2017
In this extended abstract, we discuss the interaction design of AS IF, a serious game that employ... more In this extended abstract, we discuss the interaction design of AS IF, a serious game that employs embodied interaction in order to facilitate perspective taking. The goal of this game is to offer non-patients an insight into what it may feel like to function with a body that is, at times, disabled or limited because of Chronic Pain. The interactor controls an avatar by means of skeletal tracking. In this way, the avatar mimics the interactor's movements and gestures in the virtual environment where they complete a series of tasks. The tasks require the interactor to reach out in physical space with their hands to have the avatar touch objects in the virtual space. During the game, we introduce range of motion limitations to the avatar, effectively making it more difficult to complete the motor tasks in the game environment. Through this "disabling" feature, the interactor's actions are deliberately mapped incorrectly to the avatar; the aim is to give the interactor a glimpse into what it may be like to live with constraints-a frustrating experience.
Virtual reality event. A collaborative work between Diane Gromala and Yacov Sharir. Body, archite... more Virtual reality event. A collaborative work between Diane Gromala and Yacov Sharir. Body, architecture, and virtual reality. Choreographic material from the first Dervish Dance. Pursued and designed in Banff Center for the Arts. First performed in the spring of 1992. Sponsored by Banff Centre for the Arts (Canada), and the National Endowment for the Arts.
Wearable trackers and mobile applications can facilitate self-reflection of doing physical activi... more Wearable trackers and mobile applications can facilitate self-reflection of doing physical activity. The gamification process incorporates game design elements with persuasive systems in order to encourage more physical activity. However, few gamification strategies have been rigorously evaluated; these investigations showed that using the same gamification mechanism to promote physical activity could have contradictory effects. Therefore, I developed FitPet, a virtual pet-keeping mobile game for encouraging activity. I evaluated its effectiveness, and compared it with the goal-setting and social community strategies in a six-week field study. The findings revealed social interaction were the most effective intervention. Contrary to prior research, goal-setting was not perceived as an effective way to provide motivation compared to social interaction overall. Although FitPet was not able to promote significantly higher activity, participants showed great interests in this approach and provided design insights for future research: implementing social components and more challenging gameplay.
Non-technical end-users are silent and invisible users of the state-of-the-art explainable artifi... more Non-technical end-users are silent and invisible users of the state-of-the-art explainable artificial intelligence (XAI) technologies. Their demands and requirements for AI explainability are not incorporated into the design and evaluation of XAI techniques, which are developed to explain the rationales of AI decisions to end-users and assist their critical decisions. This makes XAI techniques ineffective or even harmful in high-stakes applications, such as healthcare, criminal justice, finance, and autonomous driving systems. To systematically understand end-users' requirements to support the technical development of XAI, we conducted the EUCA user study with 32 layperson participants in four AI-assisted critical tasks. The study identified comprehensive user requirements for feature-, example-, and rulebased XAI techniques (manifested by the enduser-friendly explanation forms) and XAI evaluation objectives (manifested by the explanation goals), which were shown to be helpful to directly inspire the proposal of new XAI algorithms and evaluation metrics. The EUCA study findings, the identified explanation forms and goals for technical specification, and the EUCA study dataset support the design and evaluation of end-user-centered XAI techniques for accessible, safe, and accountable AI.
The ability to explain decisions to end-users is a necessity to deploy AI as critical decision su... more The ability to explain decisions to end-users is a necessity to deploy AI as critical decision support. Yet making AI explainable to non-technical end-users is a relatively ignored and challenging problem. To bridge the gap, we first identify twelve end-userfriendly explanatory forms that do not require technical knowledge to comprehend, including feature-, example-, and rule-based explanations. We then instantiate the explanatory forms as prototyping cards in four AI-assisted critical decision-making tasks, and conduct a user study to co-design low-fidelity prototypes with 32 layperson participants. The results confirm the relevance of using explanatory forms as building blocks of explanations, and identify their proprieties-pros, cons, applicable explanation goals, and design implications. The explanatory forms, their proprieties, and prototyping supports (including a suggested prototyping process, design templates and exemplars, and associated algorithms to actualize explanatory forms) constitute the End-User-Centered explainable AI framework EUCA, and is available at http://weinajin.github.io/end-user-xai. It serves as a practical prototyping toolkit for HCI/AI practitioners and researchers to understand user requirements and build end-user-centered explainable AI. CCS Concepts: • Computing methodologies → Artificial intelligence; • Human-centered computing → User studies.
In this poster, we present a pilot study on the efficacy of adherence by adding social components... more In this poster, we present a pilot study on the efficacy of adherence by adding social components into LumaPath, an Immersive Virtual Environment (IVE) built for motivating chronic pain patients to perform range of motion (RoM) exercises, especially aging patients who live with Rheumatoid Arthritis (RA) and Osteoarthritis (OA). Based on results from this pilot study as well as from prior work, we propose that adding a certain level of social presence for patients in an IVE such as LumaPath may positively influence their adherence to using assistive tools for treating arthritis and chronic pain. CCS CONCEPTS • Human-centered computing → Virtual reality; Collaborative and social computing theory, concepts and paradigms.
ABSTRACT Body image/body schema (BIBS) is within the larger realm of embodied cognition. Its inte... more ABSTRACT Body image/body schema (BIBS) is within the larger realm of embodied cognition. Its interdisciplinary literature can inspire Virtual Reality (VR) researchers and designers to develop novel ideas and provide them with approaches to human perception and experience. In this paper, we introduced six fundamental ideas in designing interactions in VR, derived from BIBS literature that demonstrates how the mind is embodied. We discuss our own research, ranging from two mature works to a prototype, to support explorations VR interaction design from a BIBS approach. Based on our experiences, we argue that incorporating ideas of embodiment into design practices requires a shift in the perspective or understanding of the human body, perception and experiences, all of which affect interaction design in unique ways. The dynamic, interactive and distributed understanding of cognition guides our approach to interaction design, where the interrelatedness and plasticity of BIBS play a crucial role.
We plan to conduct a longitudinal mixed-methods study to evaluate the impact of home-use Virtual ... more We plan to conduct a longitudinal mixed-methods study to evaluate the impact of home-use Virtual Reality (VR) for chronic pain (CP) management with cancer survivors over a six-week period. The participants will play VR games for a minimum of 30 min per day for at least three days per week. Each week, the participants are required to use randomly assigned VR content from a group of VR titles that ranged from commercially-available VR games to VR meditation designed specifically for people with CP. Well before launching the longitudinal study, we compiled, tested, categorized and eliminated commercial VR titles, and developed a short list that varied by genre and methods of interaction. Therefore, to better understand which are the best VR games to use, how to offer good VR gaming experiences, and validate our choices, we compared CP patients’ experiences of some selected games in VR and non-VR conditions in this research. Seven pain patients took part in the focus group study; initial results suggest participants preferred VR conditions compared to PC games according to both of the quantitative ratings and the qualitative interviews. They also liked puzzle-solving game mechanism comparing to exploration games. Participants also mentioned that the platform (VR vs. PC monitor) is more important than the actual content. This result will be helpful for the researchers to select proper VR games to test in the longitudinal study for pain distraction and management purposes since it has been done with patients.
One in five people in North America experience chronic pain. The primary non-pharmacological appr... more One in five people in North America experience chronic pain. The primary non-pharmacological approach to treat chronic pain is to 'manage' pain by practices like Mindfulness-based Stress Reduction (MBSR) Meditation. Previous research shows the potential of mindfulness meditation to help foster patients' emotional wellbeing and pain self-modulation. Thus, the Virtual Reality (VR) system named "Virtual Meditative Walk" (VMW) was developed to help patients direct their attention inward through mindfulness meditation, which incorporates biofeedback sensors, an immersive virtual environment, and stereoscopic sound. It was specifically designed to help patients to learn MBSR meditation by providing real-time feedback, and to provide further training reinforcement. VMW enables patients to manage their chronic pain by providing real-time immersive visual signals and sonic feedback, which are mapped to their physiological biofeedback data. In the proof-of-concept study, this combination of immersive VR and MBSR meditation pain self-modulation technique proved to be effective for managing chronic pain.
IS&T International Symposium on Electronic Imaging Science and Technology, Feb 14, 2016
Immersive Virtual Reality (VR) has been shown to work as a non-pharmacological analgesic by induc... more Immersive Virtual Reality (VR) has been shown to work as a non-pharmacological analgesic by inducing [sic] cognitive distraction in acute pain patients. Researchers have shown that VR games have the potential to distract patients cognitively and function as a type of pain management therapy. In this paper, we introduce the gameplay and design metaphors of Mobius Floe (MF), an immersive VR pain distraction game for acute and chronic pain patients. MF introduces an experimental approach with more engaging game interactivity to improve cognitive distraction for pain relief. In MF, we designed game mechanics with specific pain metaphors and therapeutic elements in immersive VR. In this paper, we analyze and explain the overall gameplay design principles and each pain metaphor element implemented in the game. We believe the design procedures and the way we implemented pain metaphors will inspire game design ideas in VR health game design and provide potentially useful references for other researchers and game designers.
Although Virtual Reality (VR) applications have been shown to reduce many forms of acute pain, su... more Although Virtual Reality (VR) applications have been shown to reduce many forms of acute pain, such research of VR applications and their effects on chronic pain is still at its infancy. In this study, we designed a VR game Cryoslide, and examined its analgesic effect on chronic pain patients, its end users, in a clinical setting. In this randomized, controlled crossover clinical study of 20 chronic pain patients, Cryoslide significantly reduced perceived pain compared to the baseline and the control group. The results demonstrate that Cryoslide can be effectively used as an analgesic intervention for chronic pain management to lessen pain intensity during short-term symptom spikes.
In this paper, we address the issue of sound mapping in virtual environments (VEs). Currently, th... more In this paper, we address the issue of sound mapping in virtual environments (VEs). Currently, the use of sound in virtual environments is shifting towards adaptive or generative techniques in which sound no longer has a static quality but is dynamic via real-time controls that modify the tonal characteristics over time. We build upon the acoustic communication model posited by Barry Truax by examining two aspects: how sound mediates information and its importance to the listener through cognitive processing. Using this model and investigating the qualitative aspects of soundwalks, soundscape composition, and sound in virtual reality (VR), we present a hybrid model, which addresses the use of procedural sound design techniques to enhance the communicative and pragmatic role of sound in virtual environments. The end result produces a sonic environment that heightens the listeners' experience and cognitively engages them to sounds within a specific time and space.
Background: Many researchers have been evaluating how digital media may impact the emotional and ... more Background: Many researchers have been evaluating how digital media may impact the emotional and perspective taking aspects of empathy in both clinical and nonclinical settings. Despite the growing interest in using virtual reality (VR) and VR games to motivate empathy, few studies have focused on empathy for people who live with chronic pain. Objective: Chronic pain affects, by conservative estimates, 1 in 5 people in industrialized countries. Despite this prevalence, public awareness of chronic pain was remarkably low until the recent opioid crisis; as a result, stigma remains a problem frequently faced by people who live with this condition. To address this, the VR game AS IF was developed to increase nonpatients' empathy toward the growing number of people who live with long-term chronic pain. On the basis of our prior work, we overhauled our approach, designed and built a VR prototype and evaluated it, and offered design suggestions for future research. Methods: We introduced the design features of the VR game AS IF and described the study we devised to evaluate its effectiveness. We adopted a mixed methods approach and compared the empathy-related outcomes in both pre-and posttesting. A total of 19 participants were recruited. Results: The findings of this study suggest that the VR game was effective in improving implicit and explicit empathy as well as its emotional and perspective taking aspects. More specifically, for the Empathy Scale, the total pretest scores (mean 47.33, SD 4.24) and posttest scores (mean 59.22, SD 4.33) did not reach statistical significance (P=.08). However, we did find differences in the subscales. The kindness subscale showed a statistically significant increase in the posttest score (mean 15.61, SD 2.85) compared with the pretest score (mean 17.06, SD 2.65;P=.001). For the Willingness to Help Scale, a significant increase was observed from a t test analysis (P<.001) of scores before (mean 7.17, SD 2.28) and after (mean 8.33, SD 2.03) the gameplay. The effect size for this analysis was large (d=−1.063). Conclusions: The contributions of this research are as follows: AS IF provides a promising approach for designing VR games to motivate people's empathy toward patients with chronic pain, the study evaluates the potential effectiveness of such a VR approach, and the general design suggestions devised from this study could shed light on future VR game systems.
Communications in computer and information science, 2017
In this extended abstract, we discuss the interaction design of AS IF, a serious game that employ... more In this extended abstract, we discuss the interaction design of AS IF, a serious game that employs embodied interaction in order to facilitate perspective taking. The goal of this game is to offer non-patients an insight into what it may feel like to function with a body that is, at times, disabled or limited because of Chronic Pain. The interactor controls an avatar by means of skeletal tracking. In this way, the avatar mimics the interactor's movements and gestures in the virtual environment where they complete a series of tasks. The tasks require the interactor to reach out in physical space with their hands to have the avatar touch objects in the virtual space. During the game, we introduce range of motion limitations to the avatar, effectively making it more difficult to complete the motor tasks in the game environment. Through this "disabling" feature, the interactor's actions are deliberately mapped incorrectly to the avatar; the aim is to give the interactor a glimpse into what it may be like to live with constraints-a frustrating experience.
Virtual reality event. A collaborative work between Diane Gromala and Yacov Sharir. Body, archite... more Virtual reality event. A collaborative work between Diane Gromala and Yacov Sharir. Body, architecture, and virtual reality. Choreographic material from the first Dervish Dance. Pursued and designed in Banff Center for the Arts. First performed in the spring of 1992. Sponsored by Banff Centre for the Arts (Canada), and the National Endowment for the Arts.
Wearable trackers and mobile applications can facilitate self-reflection of doing physical activi... more Wearable trackers and mobile applications can facilitate self-reflection of doing physical activity. The gamification process incorporates game design elements with persuasive systems in order to encourage more physical activity. However, few gamification strategies have been rigorously evaluated; these investigations showed that using the same gamification mechanism to promote physical activity could have contradictory effects. Therefore, I developed FitPet, a virtual pet-keeping mobile game for encouraging activity. I evaluated its effectiveness, and compared it with the goal-setting and social community strategies in a six-week field study. The findings revealed social interaction were the most effective intervention. Contrary to prior research, goal-setting was not perceived as an effective way to provide motivation compared to social interaction overall. Although FitPet was not able to promote significantly higher activity, participants showed great interests in this approach and provided design insights for future research: implementing social components and more challenging gameplay.
Non-technical end-users are silent and invisible users of the state-of-the-art explainable artifi... more Non-technical end-users are silent and invisible users of the state-of-the-art explainable artificial intelligence (XAI) technologies. Their demands and requirements for AI explainability are not incorporated into the design and evaluation of XAI techniques, which are developed to explain the rationales of AI decisions to end-users and assist their critical decisions. This makes XAI techniques ineffective or even harmful in high-stakes applications, such as healthcare, criminal justice, finance, and autonomous driving systems. To systematically understand end-users' requirements to support the technical development of XAI, we conducted the EUCA user study with 32 layperson participants in four AI-assisted critical tasks. The study identified comprehensive user requirements for feature-, example-, and rulebased XAI techniques (manifested by the enduser-friendly explanation forms) and XAI evaluation objectives (manifested by the explanation goals), which were shown to be helpful to directly inspire the proposal of new XAI algorithms and evaluation metrics. The EUCA study findings, the identified explanation forms and goals for technical specification, and the EUCA study dataset support the design and evaluation of end-user-centered XAI techniques for accessible, safe, and accountable AI.
The ability to explain decisions to end-users is a necessity to deploy AI as critical decision su... more The ability to explain decisions to end-users is a necessity to deploy AI as critical decision support. Yet making AI explainable to non-technical end-users is a relatively ignored and challenging problem. To bridge the gap, we first identify twelve end-userfriendly explanatory forms that do not require technical knowledge to comprehend, including feature-, example-, and rule-based explanations. We then instantiate the explanatory forms as prototyping cards in four AI-assisted critical decision-making tasks, and conduct a user study to co-design low-fidelity prototypes with 32 layperson participants. The results confirm the relevance of using explanatory forms as building blocks of explanations, and identify their proprieties-pros, cons, applicable explanation goals, and design implications. The explanatory forms, their proprieties, and prototyping supports (including a suggested prototyping process, design templates and exemplars, and associated algorithms to actualize explanatory forms) constitute the End-User-Centered explainable AI framework EUCA, and is available at http://weinajin.github.io/end-user-xai. It serves as a practical prototyping toolkit for HCI/AI practitioners and researchers to understand user requirements and build end-user-centered explainable AI. CCS Concepts: • Computing methodologies → Artificial intelligence; • Human-centered computing → User studies.
In this poster, we present a pilot study on the efficacy of adherence by adding social components... more In this poster, we present a pilot study on the efficacy of adherence by adding social components into LumaPath, an Immersive Virtual Environment (IVE) built for motivating chronic pain patients to perform range of motion (RoM) exercises, especially aging patients who live with Rheumatoid Arthritis (RA) and Osteoarthritis (OA). Based on results from this pilot study as well as from prior work, we propose that adding a certain level of social presence for patients in an IVE such as LumaPath may positively influence their adherence to using assistive tools for treating arthritis and chronic pain. CCS CONCEPTS • Human-centered computing → Virtual reality; Collaborative and social computing theory, concepts and paradigms.
ABSTRACT Body image/body schema (BIBS) is within the larger realm of embodied cognition. Its inte... more ABSTRACT Body image/body schema (BIBS) is within the larger realm of embodied cognition. Its interdisciplinary literature can inspire Virtual Reality (VR) researchers and designers to develop novel ideas and provide them with approaches to human perception and experience. In this paper, we introduced six fundamental ideas in designing interactions in VR, derived from BIBS literature that demonstrates how the mind is embodied. We discuss our own research, ranging from two mature works to a prototype, to support explorations VR interaction design from a BIBS approach. Based on our experiences, we argue that incorporating ideas of embodiment into design practices requires a shift in the perspective or understanding of the human body, perception and experiences, all of which affect interaction design in unique ways. The dynamic, interactive and distributed understanding of cognition guides our approach to interaction design, where the interrelatedness and plasticity of BIBS play a crucial role.
We plan to conduct a longitudinal mixed-methods study to evaluate the impact of home-use Virtual ... more We plan to conduct a longitudinal mixed-methods study to evaluate the impact of home-use Virtual Reality (VR) for chronic pain (CP) management with cancer survivors over a six-week period. The participants will play VR games for a minimum of 30 min per day for at least three days per week. Each week, the participants are required to use randomly assigned VR content from a group of VR titles that ranged from commercially-available VR games to VR meditation designed specifically for people with CP. Well before launching the longitudinal study, we compiled, tested, categorized and eliminated commercial VR titles, and developed a short list that varied by genre and methods of interaction. Therefore, to better understand which are the best VR games to use, how to offer good VR gaming experiences, and validate our choices, we compared CP patients’ experiences of some selected games in VR and non-VR conditions in this research. Seven pain patients took part in the focus group study; initial results suggest participants preferred VR conditions compared to PC games according to both of the quantitative ratings and the qualitative interviews. They also liked puzzle-solving game mechanism comparing to exploration games. Participants also mentioned that the platform (VR vs. PC monitor) is more important than the actual content. This result will be helpful for the researchers to select proper VR games to test in the longitudinal study for pain distraction and management purposes since it has been done with patients.
One in five people in North America experience chronic pain. The primary non-pharmacological appr... more One in five people in North America experience chronic pain. The primary non-pharmacological approach to treat chronic pain is to 'manage' pain by practices like Mindfulness-based Stress Reduction (MBSR) Meditation. Previous research shows the potential of mindfulness meditation to help foster patients' emotional wellbeing and pain self-modulation. Thus, the Virtual Reality (VR) system named "Virtual Meditative Walk" (VMW) was developed to help patients direct their attention inward through mindfulness meditation, which incorporates biofeedback sensors, an immersive virtual environment, and stereoscopic sound. It was specifically designed to help patients to learn MBSR meditation by providing real-time feedback, and to provide further training reinforcement. VMW enables patients to manage their chronic pain by providing real-time immersive visual signals and sonic feedback, which are mapped to their physiological biofeedback data. In the proof-of-concept study, this combination of immersive VR and MBSR meditation pain self-modulation technique proved to be effective for managing chronic pain.
IS&T International Symposium on Electronic Imaging Science and Technology, Feb 14, 2016
Immersive Virtual Reality (VR) has been shown to work as a non-pharmacological analgesic by induc... more Immersive Virtual Reality (VR) has been shown to work as a non-pharmacological analgesic by inducing [sic] cognitive distraction in acute pain patients. Researchers have shown that VR games have the potential to distract patients cognitively and function as a type of pain management therapy. In this paper, we introduce the gameplay and design metaphors of Mobius Floe (MF), an immersive VR pain distraction game for acute and chronic pain patients. MF introduces an experimental approach with more engaging game interactivity to improve cognitive distraction for pain relief. In MF, we designed game mechanics with specific pain metaphors and therapeutic elements in immersive VR. In this paper, we analyze and explain the overall gameplay design principles and each pain metaphor element implemented in the game. We believe the design procedures and the way we implemented pain metaphors will inspire game design ideas in VR health game design and provide potentially useful references for other researchers and game designers.
Although Virtual Reality (VR) applications have been shown to reduce many forms of acute pain, su... more Although Virtual Reality (VR) applications have been shown to reduce many forms of acute pain, such research of VR applications and their effects on chronic pain is still at its infancy. In this study, we designed a VR game Cryoslide, and examined its analgesic effect on chronic pain patients, its end users, in a clinical setting. In this randomized, controlled crossover clinical study of 20 chronic pain patients, Cryoslide significantly reduced perceived pain compared to the baseline and the control group. The results demonstrate that Cryoslide can be effectively used as an analgesic intervention for chronic pain management to lessen pain intensity during short-term symptom spikes.
In this paper, we address the issue of sound mapping in virtual environments (VEs). Currently, th... more In this paper, we address the issue of sound mapping in virtual environments (VEs). Currently, the use of sound in virtual environments is shifting towards adaptive or generative techniques in which sound no longer has a static quality but is dynamic via real-time controls that modify the tonal characteristics over time. We build upon the acoustic communication model posited by Barry Truax by examining two aspects: how sound mediates information and its importance to the listener through cognitive processing. Using this model and investigating the qualitative aspects of soundwalks, soundscape composition, and sound in virtual reality (VR), we present a hybrid model, which addresses the use of procedural sound design techniques to enhance the communicative and pragmatic role of sound in virtual environments. The end result produces a sonic environment that heightens the listeners' experience and cognitively engages them to sounds within a specific time and space.
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Papers by Diane Gromala