Obesity Therapy in VR: The Influence of Immersion on Presence, Embodiment and Body Perception

Closed Human-Computer Interaction Master Thesis No Affiliation

Motivation

The numbers for obesity and overweight have risen worldwide in recent decades (WHO, 2016). This results in secondary diseases such as diabetes or cardiovascular disorders, a correspondingly higher mortality rate, and the associated high costs for our social system (Klein, Krupka, Behrendt, Pulst, & Bleß, 2016). Existing therapies show good short-term successes, but in many cases, a renewed weight gain occurs in the long term. The reasons for the high number of cases and the lack of sustainability of therapies are manifold (Clark, 2015). A substantial part, however, is allegedly due to a disturbed body image (Thompson, 2001). Various studies show that obesity patients often perceive their body dimensions differently (Moelbert et al., 2017). Through the use of Virtual Reality (VR), a sustainable reorientation of the self-image can be encouraged (Normand, Giannopoulos, Spanlang, & Slater, 2011). However, studies on body perception with the help of avatars in VR show different results. Many factors such as the personalization and quality of the avatars, the degree of embodiment, and the degree of immersion of the medium used seem to influence the perception of a virtual mirror image’s appearance (Nimcharoen, Zollmann, Collins, & Regenbrecht, 2019; Piryankova et al., 2014; Thaler et al., 2018). In this thesis, the effects of the degree of immersion of a medium on the perception of a virtual mirror image shall be investigated. Specifically, we will investigate how the type of medium (VR vs. AR) affects the sense of embodiment, presence, and body size perception. It is assumed that a higher immersion increases the sense of embodiment as well as the presence and thus enables a more precise perception of the body dimensions of a self-embodied avatar.

Goal

The aim of this work is to gain new insights into the influence of immersion on body perception in VR and it’s mediation through presence and embodiment.

System Description

The experimental environment is implemented in Unity and displayed via HTC Vive HMD. In this environment, the participant receives a fully animated generic avatar animated according to his own body movements. The virtual environment corresponds to the physical space. The avatars used are either generated with the dynamic avatar generator “UMA” or unpersonalized scanned avatars. The body tracking is realized by a combination of Vive Trackers and Inverse Kinematic (Final IK). The experimental data is collected via Unity logfiles and LimeSurvey.

Experimental Design

The design was developed according to various preliminary works (Latoschik, Lugrin, & Roth, 2016; Latoschik et al., 2017; Lugrin, Latt, & Latoschik, 2015; Nimcharoen et al., 2019; Thaler, Geuss, et al., 2018; Waltemate, Gall, Roth, Botsch, & Latoschik, 2018). In a virtual environment, test persons see a mirror image in the form of an avatar animated by their own body movements in a virtual mirror. The mirror is located in a simple, physical space.

Tasks

In order to create visuomotor synchronicity, the participant receives various motor tasks, which he must perform. After the performance of the tasks, the respondent has to answer appropriate questionnaires.

Movement instructions to induce presence and embodiment e.g.:

1. “Stretch out both arms to the front and perform circular movements.”
2. “Look at the movement in the mirror and afterward on your own body.“
3. „Please do not touch your own body.”
4. „Please answer to the following questions.“

Independent variables

• Degree of immersion (High immersion vs. Low immersion)

Properties of immersion:

• Type of Display ( VR HMD vs. AR HMD)
• Field of View (Wide vs. Narrow)
• Object Occlusion (Full occlusion vs. Partly see-through)

Dependent variables

Mid-immersion:

• Presence (Mid-immersion question)
• Embodiment (Mid-immersion questions)
• Body perception (Mid-immersion weight estimation / big or smaller question)

Post-immersion:

• Presence (MEC-SPQ)
• Embodiment (Gold IVBO)

Participant variables

Pre:

• Demographic data
• Self-information on eating disorders
• Body mass index (BMI)
• Pre-simulator sickness questionnaire (SSQ)
• Self-esteem questionnaire
• Body image assessment for obesity (BIA-O)
• Body shape questionnaire short version (BSQ)
• Sociocultural Attitudes Towards Appearance Questionnaire (SATAQ-4)

Post:

• Post-simulator sickness (SSQ)
• Post-experimental qustionnaire

Design

• Between-subjects design (Degree of Immersion)

Analysis

• Pair comparisons (ANOVA)

Figure 1. Analysingthe influence of immersion on presence and embodiment.

• Covariance analysis (ANCOVA)

Figure 2. Analysing the influence of immersion on body weight perception purged by the influence of BMI

• Mediation analysis

Figure 3. Mediation analysis of presence and embodiment on body weight perception.

Hypotheses

• H1: Participants with a higher degree of immersion perceive a higher subjective sense of presence and sense of embodiment.
• H2: BMI purged body weight perception differs between a high and low degree of immersion.
• H3: The influence of immersion on body perception is mediated by presence and embodiment.

Time Schedule

Figure 4. Time schedule of the project

Contribution

• Insights on what and how immersive factors influence presence, embodiment, and body perception in VR
• Development of a software framework to test the influence of immersive factors on psychophysical factors

Future Work

• Investigation of the influence of different immersive factors on presence, embodiment, and body perception in VR
• In long term, development of methods to support obesity therapy in VR

References

Clark, J. E. (2015). Diet, exercise or diet with exercise: comparing the effectiveness of treatment options for weight-loss and changes in fitness for adults (18–65 years old) who are overfat, or obese; systematic review and meta-analysis. Journal of Diabetes & Metabolic Disorders, 14(1), 31.

Klein, S., Krupka, S., Behrendt, S., Pulst, A., & Bleß, H.-H. (2016). Weißbuch Adipositas. Versorgungssituation in Deutschland. MWVMedizinisch Wissenschaftliche Verlagsgesellschaft, Berlin.

Latoschik, M. E., Lugrin, J.-L., & Roth, D. (2016). FakeMi: a fake mirror system for avatar embodiment studies. Paper presented at the Proceedings of the 22nd ACM Conference on Virtual Reality Software and Technology.

Latoschik, M. E., Roth, D., Gall, D., Achenbach, J., Waltemate, T., & Botsch, M. (2017). The effect of avatar realism in immersive social virtual realities. Paper presented at the Proceedings of the 23rd ACM Symposium on Virtual Reality Software and Technology.

Lugrin, J.-L., Latt, J., & Latoschik, M. E. (2015). Anthropomorphism and illusion of virtual body ownership. Paper presented at the Proceedings of the 25th International Conference on Artificial Reality and Telexistence and 20th Eurographics Symposium on Virtual Environments.

Moelbert, S. C., Klein, L., Thaler, A., Mohler, B. J., Brozzo, C., Martus, P., . . . Giel, K. E. (2017). Depictive and metric body size estimation in anorexia nervosa and bulimia nervosa: A systematic review and meta-analysis. Clinical psychology review, 57, 21-31.

Nimcharoen, C., Zollmann, S., Collins, J., & Regenbrecht, H. (2019). Is That Me?—Embodiment and Body Perception with an Augmented Reality Mirror. Paper presented at the 2018 IEEE International Symposium on Mixed and Augmented Reality Adjunct (ISMAR-Adjunct).

Normand, J.-M., Giannopoulos, E., Spanlang, B., & Slater, M. (2011). Multisensory stimulation can induce an illusion of larger belly size in immersive virtual reality. PloS one, 6(1).

Piryankova, I. V., Stefanucci, J. K., Romero, J., De La Rosa, S., Black, M. J., & Mohler, B. J. (2014). Can I recognize my body’s weight? The influence of shape and texture on the perception of self. ACM Transactions on Applied Perception (TAP), 11(3), 13.

Thaler, A., Geuss, M. N., Mölbert, S. C., Giel, K. E., Streuber, S., Romero, J., . . . Mohler, B. J. (2018). Body size estimation of self and others in females varying in BMI. PloS one, 13(2).

Thaler, A., Piryankova, I., Stefanucci, J. K., Pujades, S., de la Rosa, S., Streuber, S., . . . Mohler, B. J. (2018). Visual Perception and Evaluation of Photo-Realistic Self-Avatars From 3D Body Scans in Males and Females. Frontiers in ICT, 5.

Thompson, J. (2001). Body image, eating disorders, and obesity: An integrative guide for assessment and treatment. American Psychological Association.

Waltemate, T., Gall, D., Roth, D., Botsch, M., & Latoschik, M. E. (2018). The Impact of Avatar Personalization and Immersion on Virtual Body Ownership, Presence, and Emotional Response. IEEE transactions on visualization and computer graphics, 24(4), 1643-1652.

WHO. (2016). Obesity and overweight. Retrieved from https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight

Contact Persons at the University Würzburg