The role of semantic congruence on body ownership illusions within immersive virtual environments
Konstantina Kilteni · Dipòsit Digital de la Universitat de Barcelona (Universitat de Barcelona) · 2014
[eng] During the last two decades, a plethora of experimental studies in neuroscience and psychology have challenged the rigidity of our feelings that our body belongs to us and is the source of our associated sensations, by demonstrating the possibility of experiencing similar feelings towards artificial body-parts or bodies. Recent experimental evidence suggests that the visual form of these fake body counterparts plays a significant role in the development of such Body Ownership Illusions, having at the same time an influential impact on our body and self-perception. The aim of this thesis is to study the contribution of Semantic Congruence between the real and such alternative body representations. Using Immersive Virtual Reality, we created perceptual illusions of Body Ownership towards virtual bodies that differed substantially from the real ones in terms of body proportions, body integrity and demographic characteristics. We addressed systematically the role of semantic violations in terms of body proportions to the induction of Body Ownership Illusions, and we further explored how feelings of having a different body in terms of demographic or body impairment characteristics can influence one’s behavioural and physiological state. Three different studies were designed, implemented and tested on healthy adults to address perceptual, behavioural, physiological and neurophysiological correlates of Body Ownership Illusions towards transformed bodies. In the Long Arm Study, we tested the extent to which gross asymmetries in the fake body can be assimilated. A body ownership illusion was induced to healthy adults towards an asymmetric virtual body with a very long limb. Despite the substantial violation of human body proportions, our results showed that participants experienced the illusion of ownership towards the virtual limb of length up to three times the real one, and indicated an adaptation of their body space and its associate defensive mechanisms to match the transformed virtual body. Overall, our findings extended and enriched previous results that multisensory and sensorimotor information can reconstruct our perception of the body shape, size and symmetry even when this is not consistent with normal body proportions. In the Drumming Study, we investigated the perceptual, behavioural and attitudinal consequences of a body ownership illusion towards an artificial body that diverged significantly from the real in terms of demographic characteristics including skin colour. Despite the morphological differences, our results revealed that participants experienced the body ownership illusion towards the virtual body and that they further adapted their behavioural patterns according to their new body representation. Overall, our findings demonstrated that body ownership illusions can lead to substantial behavioural and possibly cognitive changes depending on the appearance of the virtual body. In the Amputee Study, we explored whether intact human adults can experience a body ownership illusion towards an artificial body that appeared anatomically impaired, that is missing a part of its right limb. Despite the impairment of the virtual body, the pattern of our results provided evidence that participants experienced the body ownership illusion towards the virtual body together with an apparent loss of their real limb, which was sequentially reflected in changes of its physiological and neurophysiological state. All together, the outcome of our research argues in favour of great flexibility in our body perception in overcoming semantic violations with respect to the real body,at least at the level of body proportions, body integrity and demographic characteristics.