In the rubber hand illusion (RHI), a rubber hand is placed in front of the participant with the participant's hand out of sight. If both hands are touched simultaneously, the illusion typically occurs. Between RHI studies, differences can be seen in the setup, and results of the illusion strength are inconsistent. One of these differences can be the moving RHI, where the real and rubber hand make the same movements to induce the illusion. The differences led to uncertainty regarding the influence of spatial configuration (i.e., an arrangement of the setup within three-dimensional space) on the illusion of body ownership. With this meta-analysis, I quantify the illusion strength in the moving RHI to be able to conclude if spatial configuration influences the results. A total of nine studies were included that had a total of 391 participants. The results show that the synchronous condition has a stronger illusory effect than the asynchronous condition. However, due to heterogeneity, the sample size may not represent the general population. Sub-group analysis showed no major difference in the illusion strength between a vertical and horizontal setup. These observations do not correspond with classical RHI studies in which vertical and horizontal setups were compared. However, in this meta-analysis, only moving RHI studies were included. In the moving RHI, the experimenter does not enter the visual receptive field of the participant, which may explain why no differences between the setups were found. The results of this meta-analysis cannot be seen as definitive; more research is necessary.

Embodiment is the experience of one's own body. It is often studied using the Rubber Hand Illusion (RHI). This illusion varies the consistency between visual, tactile and proprioceptive signals to elicit a change to embodiment. Changes to embodiment are typically measured using a single sensory outcome measure of proprioceptive drift, which is interpreted as a proxy measure of embodiment. This approach obscures the unique contribution of other modalities such as vision and touch. The work presented in this thesis uses a mixed method approach to investigate the unique contribution of visual, tactile and proprioceptive modalities within the multisensory process of embodiment. In study one, a qualitative analysis showed that when visual-tactile discrepancies were present in the RHI, participants described both body ownership and body extension type changes to embodiment, and changes to tactile perception. In study two, psychophysical measurements of the RHI showed changes to visual, tactile and proprioceptive aspects of embodiment, suggesting that embodiment in the RHI could be measured using multiple sensory outcomes. Studies three and four assessed the utility of measuring multiple sensory outcomes of the RHI, by exploring changes to embodiment following internal and external forms of body perception training. Study three showed that brief body scan meditation, as a form of internal body perception training, reduced the longevity of the visual sensory outcome of the RHI and that this reduction was negatively correlated with improvements in interoceptive sensitivity. Study four showed that learning about the body through anatomical dissection training, as a form of external body perception training, reduced the longevity of the visual sensory outcome measure and decreased interoceptive sensitivity, but only in medical students who were high in trait personal distress. Collectively, these findings suggest that aspects of the multisensory processes of embodiment can become specialised and identify some unique contributions of individual sensory modalities to embodiment. The proprioceptive sensory outcome appears to be stable over time but the visual sensory outcome is a longer-term change to embodiment, which is susceptible to interference from body perception training. In study five, confirmatory factor analysis was used to assess the psychometric properties of an embodiment change questionnaire measuring body ownership, body extension and perceived causality in the RHI. Factor scores from the questionnaire were correlated with visual and proprioceptive outcome measures of the RHI and measures of trait empathy. The results suggested factor scores had better convergent validity than the standard illusion score used in previous research. This work has improved subjective and perceptual measures of the RHI and specified ways that individual sensory modalities provide a unique contribution to embodiment. The methods developed have further applications for studying the multisensory process of embodiment and investigating embodiment in a number of clinical groups.

The feeling of owning a body part is often investigated by conducting and manipulating the rubber hand illusion, a three-way integration of vision, touch, and proprioception. In the last decade, more research on the role of interoception, the sense of the body's’ internal state, in the illusion has been made. One of the studied factors has been the affective touch, a caress-like, gentle, touch that is performed at a slow specific speed (1-10 cm/sec). Affective touch activates the C tactile afferents which send interoceptive signals to the brain, specifically the insula. The present systematic review investigated the role affective touch has on the strength of the rubber hand illusion. A range of electronic databases was searched for papers reporting research findings published in English before March 20, 2020. Twelve different articles were identified, but only five papers met the inclusion criteria. This thesis looked at the results from these five different studies and compared the effect of affective touch and discriminative, regular, touch have on the rubber hand illusion to see whether there is a significant difference. The results could not show a main effect of stroking velocity, site of stimulation, or social touch, which are components of affective touch. The results was based on four different measurements, the subjective experience of the illusion, pleasantness ratings, proprioceptive drift, and temperature difference in the skin. Opposed what was hypothesized, it could not be demonstrated that affective touch would induce a stronger rubber hand illusion than discriminative touch.

Body ownership can be studied via the rubber hand illusion (RHI), in which an artificial limb can be perceived as belonging to oneself. In the so-called moving RHI paradigm, both body ownership and sense of agency, induced by self-produced movements, can be investigated. The key question of this approach is whether movements generated by oneself increase the illusion of body ownership. Thus far, the results from moving RHI studies are inconsistent.This has led to uncertainty regarding the influences of the motor control mechanism on body ownership. Therefore, this study will present the first meta-analysis on moving RHI to estimate the illusory effectiveness induced by self-produced movements. A total of 23 experimental comparisons with 821 subjects were included in the meta-analysis. The results showed that the overall illusory effect induced by self-produced movements was superior toits control (e.g., asynchronous active movements) (Hedge’s g = 1.38, p < 0.001). However, due to dissimilarity in results between the studies, the sample size in the meta-analysis may not represent the general population. The subgroup analysis showed that studies using physical hands, such as wooden hands, yielded the largest effect compared to studies using a virtual projected hand or a video recorded image of the participant’s own hands. It can be speculated whether a three-dimensional hand with “realness” has an illusory advantage compared to hands presented in virtual or video image settings. Future studies need to apply aunified framework, particularly in experimental setups and measurements. This would obtain consistent results of the strength of the illusion within the moving RHI paradigm.

The rubber hand illusion is an experimental paradigm that induces the illusion of ownership over a fake hand. The illusion was originally induced using visuotactile stimulation but can also be induced using movements. Self-produced movements are active movements, and if they are produced by external force, they are passive movements. According to the comparator model, only active movements produce a sense of agency. As both passive and active movements can be used to induce the sense of ownership in the rubber hand illusion, but only active induce a sense of agency, they can be compared to determine the effect agency has on bodily ownership. This meta-analysis included nine studies with a total of 359 participants that compared the induced sense of ownership using active and passive movements in the rubber hand illusion to determine these effects. The results show that agency has a small but significant effect on body ownership.

No description available.

Body ownership is a complicated and multifaceted percept. Although we subjectively perceive body ownership to be a stable component of our identity, recent work has illustrated that body ownership is a dynamic construct that is constantly updated by the integration of current endogenous and exogenous body-related information. The goal of this study was to explore the relation between these endogenous (interoceptive) and exogenous (exteroceptive) channels of information. We investigated this by using a heartbeat perception (HBP) task to measure interoceptive accuracy, and the Rubber Hand Illusion (RHI) to measure malleability of body ownership. Based on prior findings, we hypothesized that the less accurate you are at counting your heartbeats, the more susceptible you will be to the RHI (i.e. the more malleable your sense of body ownership will be). In addition, we were also interested in exploring the relationship between interoception and emotion recognition ability (ERA). In this experiment, we failed to induce the RHI, and thus could not investigate the relationship between endogenous and exogenous body-related information. However, we successfully demonstrated the reliability of the interoceptive accuracy HBP task, as well as demonstrated that interoceptive accuracy is not related to ERA. / Thesis / Master of Science (MSc)

Our bodies are arguably one of the most intimate things we will ever know. But the comfort of our own physical boundaries can be altered in various ways. In this analysis, we will look at how vision contributes to the sense of owning a body by analysing six abnormal conditions: the rubber hand illusion, phantom limbs, somatoparaphrenia, the body-swap illusion, out-of-body experiences, and heautoscopy. Examinations of these experimental or pathological conditions has granted a greater understanding of body-ownership. It was discovered that vision plays different modulatory roles, being more intricately involved in full-body ownership than in part-body ownership. Vision appears to be highly connected to self-location and first-person perspective, which both are contributing factors in projecting the sense of ownership to an external location. In part-body ownership, however, vision can be overruled by other senses, such as proprioception. Though it is still able to contribute to the illusion of projecting ownership and proprioceptive displacement to a rubber hand.

No description available.

<p>Multiple reference frames are used to interact with our surroundings. When these reference frames are in conflict, processing errors can occur. For tactile stimuli, this conflict is highlighted when the hands are crossed over the midline of the body. In this posture, vibrotactile temporal order judgments (TOJs) presented to the hands are impaired compared to an uncrossed posture. This decrease in temporal processing is known as the crossed-hands deficit. The deficit was explored in depth throughout this thesis. In Chapters 2, 3 and 4 different elements of the crossed-hands deficit were evaluated including its connections to the rod and frame test, individual and sex differences within the TOJ task, as well as the influence of vision and body position. These elements were framed with underlying goal of investigating the root cause of the deficit. The data presented here provided evidence for a conflict model of crossed hands processing. A conflict between the internal and external reference frames produced the deficit in temporal processing when the hands were crossed. The role of the body’s midline in understanding multisensory integration was further considered in Chapter 5 through the rubber hand illusion, which is a visuotactile phenomenon whereby an unseen real hand is mislocalized towards a seen rubber hand. When the real hand, rubber hand, or both were crossed over the midline the illusion did not occur. It was hypothesized that a failure to integrate the tactile information presented to the real hand with the visual rubber hand was responsible for the absence of the illusion. Taken together, the data presented in this thesis contribute to the greater understanding of how reference frame conflicts are resolved, particularly when the conflict occurs across the body’s midline.</p> / Doctor of Philosophy (PhD)