Virtual reality allows users to experience a sense of ownership of a virtual body-a phenomenon commonly known as the body ownership illusion. Researchers and designers aim at inducing a body ownership illusion and creating embodied experiences using avatars-virtual characters that represent the user in the digital world. In accordance with the real world where humans own a body and interact via the body with the environment, avatars thereby enable users to interact with virtual worlds in a natural and intuitive fashion. Interestingly, previous work revealed that the appearance of an avatar can change the behavior, attitude, and perception of the embodying user. For example, research found that users who embodied attractive or tall avatars behaved more confidently in a virtual environment than those who embodied less attractive or smaller avatars. Alluding to the versatility of the Greek God Proteus who was said to be able to change his shape at will, this phenomenon was termed the Proteus effect. For designers and researchers of virtual reality applications, the Proteus effect is therefore an interesting and promising phenomenon to positively affect users during interaction in virtual environments. They can benefit from the limitless design space provided by virtual reality and create avatars with certain features that improve the users' interaction and performance in virtual environments. To utilize this phenomenon, it is crucial to understand how to design such avatars and their characteristics to create more effective virtual reality applications and enhanced experiences. Hence, this work explores the Proteus effect and the underlying mechanisms with the aim to learn about avatar embodiment and the design of effective avatars.
This dissertation presents the results of five user studies focusing on the body ownership of avatars, and how certain characteristics can be harnessed to make users perform better in virtual environments than they would in casual embodiments. Hence, we explore methods for inducing a sensation of body ownership of avatars and learn about perceptual and physiological consequences for the real body. Furthermore, we investigate whether and how an avatar's realism and altered body structures affect the experience. This knowledge is then used to induce body ownership of avatars with features connected with high performance in physical and cognitive tasks. Hence, we aim at enhancing the users' performance in physically and cognitively demanding tasks in virtual reality. We found that muscular and athletic avatars can increase physical performance during exertion in virtual reality. We also found that an Einstein avatar can increase the cognitive performance of another user sharing the same virtual environment. This thesis concludes with design guidelines and implications for the utilization of the Proteus effect in the context of human-computer interaction and virtual reality
