Avatar Weight Illusion - The Impact of Embodying Muscular Avatars on Weight Perception of Lifted Objects

Virtual Reality (VR) provides an immersive environment to investigate different aspects of human psychology. One phenomen even investigated back at the mind and end of the 19th century evolves around the size-wight illusion. By giving different weights in various sizes to be judged by a human participant, it could be observed that the smaller the object is, the heavier it is estimated. This was reasoned as a mainly mental effect, given that with closed eyes this effect couldn't be reproduced in the same work [1].

With the ability to create immersive environments in VR it can be investigated how strong this effect is when manipulating different variables in regard to the visual stimuli as well as the combination of haptic and visual cues. Research shows, that a higher amount of precevied immersion strengthens this illusion, while also setting different factors like the size and weight into conflict with the help of VR [2].

Another effect which is highly researched is the body ownership illusion, which is nduced by visual stimuli of the own avatar towards the player, which makes him feel that he is embodiing the avatar [3]. The illusion is often hinted to induce an additional proteus effect, which reflects different effects to the player given the avatar he is embodiing [4]. These can be improvements in their strength when embodiing muscular avatars as well as improvements in cognitive tasks when embodiing famous intelligent people while doing those [5], [6].

Keeping the effects of the proteus effect in mind, those might not just be investigated around performance aspects but also around the actual estimation and perception of weights parallel to the size-weight illusion. This hypothesis might be supported by psychological studies outside of VR, which showed the effect of assimilated action in regard to estimations [7], [8].

The main objective of the work is to investigate different influential factors of the avatar in regard to the estimation of weight. Especially influences on an avatar weight-illusion in reference to the size-weight illusion should be investigated. The main research question Q should be examined: Q: How does the avatars' muscular appearance influence percieved estimation by adjusting visual stimuli via athletic and non atheltic avatars?

Given the background around the proteus effect, the following hypothesis H can be formulated and investigatzed: H: Embodying a musuclar avatar results in a lighter estimation of the weight of the presented visual objects.

• Create one or more sample weights (ranging between 20g to 150g)
• Create and conduct a study with different avatars and weights inducing the size weight illusion.
• Usage of quesitonnaires like IPQ and analyze data from objective measures such a perceived weight, grip force, etc.
• Set data into relation with related studies using the same setup.

• Knowledge in Unity, VR and hardware
• Knowledge in perfoming studies

[1] Murray, D.J., Ellis, R.R., Bandomir, C.A. et al. Charpentier (1891) on the size—weight illusion. Perception & Psychophysics 61, 1681–1685 (1999). https://doi.org/10.3758/BF03213127

[2] Heineken, E., & Schulte, F. P. (2007). Seeing size and feeling weight: the size-weight illusion in natural and virtual reality. Human factors, 49(1), 136–144. https://doi.org/10.1518/001872007779598028

[3] Slater M, Pérez Marcos D, Ehrsson H and Sanchez-Vives MV (2009). Inducing illusory ownership of a virtual body.Front. Neurosci. 3,2:214- 220.doi: 10.3389/neuro.01.029.2009

[4] Anna Samira Praetorius and Daniel Görlich. 2020. How Avatars Influence User Behavior: A Review on the Proteus Effect in Virtual Environments and Video Games. In <i>International Conference on the Foundations of Digital Games</i> (<i>FDG '20</i>). Association for Computing Machinery, New York, NY, USA, Article 49, 1–9. DOI:https://doi.org/10.1145/3402942.3403019

[5] Martin Kocur, Melanie Kloss, Valentin Schwind, Christian Wolff, and Niels Henze. 2020. Flexing Muscles in Virtual Reality: Effects of Avatars' Muscular Appearance on Physical Performance. <i>Proceedings of the Annual Symposium on Computer-Human Interaction in Play</i>. Association for Computing Machinery, New York, NY, USA, 193–205. DOI:https://doi.org/10.1145/3410404.3414261

[6] Martin Kocur, Philipp Schauhuber, Valentin Schwind, Christian Wolff, and Niels Henze. 2020. The Effects of Self- and External Perception of Avatars on Cognitive Task Performance in Virtual Reality. In <i>26th ACM Symposium on Virtual Reality Software and Technology</i> (<i>VRST '20</i>). Association for Computing Machinery, New York, NY, USA, Article 27, 1–11. DOI:https://doi.org/10.1145/3385956.3418969

[7] Bhalla, M., & Proffitt, D. R. (1999). Visual–motor recalibration in geographical slant perception. Journal of Experimental Psychology: Human Perception and Performance, 25(4), 1076–1096. https://doi.org/10.1037/0096-1523.25.4.1076

[8] Kirsch, W., Kunde, W. Moving further moves things further away in visual perception: position-based movement planning affects distance judgments. Exp Brain Res 226, 431–440 (2013). https://doi.org/10.1007/s00221-013-3455-y