A simple experimental paradigm creates the powerful illusion that one is touching one’s own hand even when the two hands are separated by 15 cm. The participant uses her right hand to administer stimulation to a prosthetic hand while the Examiner provides identical stimulation to the participant’s receptive left hand. Change in felt position of the receptive hand toward the prosthetic hand has previously led to the interpretation that the participant experiences self-touch at the location of the prosthetic hand, and (...) experiences a sense of ownership of the prosthetic hand. Our results argue against this interpretation. We assessed change in felt position of the participant’s receptive hand but we also assessed change in felt position of the participant’s administering hand. Change in felt position of the administering hand was significantly greater than change in felt position of the receptive hand. Implications for theories of ownership are discussed. (shrink)

The effect of the body transfer illusion on the perceived strength of self- and externally-generated “tickle” sensations was investigated. As expected, externally generated movement produced significantly higher ratings of tickliness than those associated with self-generated movements. Surprisingly, the body transfer illusion had no influence on the ratings of tickliness, suggesting that highly surprising, and therefore hard to predict, experiences of body image and first-person perspective do not abolish the attenuation of tickle sensations. In addition, evidence was found that a version (...) of the rubber hand illusion exists within the body transfer illusion. We situate our findings within the larger debate over sensory attenuation: there is an attenuation of prediction errors that depends upon the context in which sensory input is predicted , and sensory attenuation is a necessary consequence of self-generated movement irrespective of context . The results support the notion of active inference. (shrink)

Two experiments report on the construction of the Sense of Agency Rating Scale (SOARS), a new measure for quantifying alterations to agency. In Experiment 1, 370 participants completed a preliminary version of the scale following hypnosis. Factor analysis revealed two underlying factors: Involuntariness and Effortlessness. In Experiment 2, this two factor structure was confirmed in a sample of 113 low, medium and high hypnotisable participants. The two factors, Involuntariness and Effortlessness, correlated significantly with hypnotisability and pass rates for ideomotor, challenge (...) and cognitive items. Twelve week test-retest correlations showed that Involuntariness was highly stable, but Effortlessness only moderately stable. Analysis of the combined datasets from Experiments 1 and 2 showed both SOARS scores were significantly related to the derived factors of Woody, Barnier, and McConkey's (2005) 4-factor model of hypnotisability. This scale clarifies conceptual confusion around agentive action and provides empirical support for a multifactorial account of sense of agency. (shrink)

A recent report in Consciousness and Cognition provided evidence from a study of the rubber hand illusion that supports the multisensory principle of inverse effectiveness . I describe two methods of assessing the principle of inverse effectiveness , and discuss how the post-hoc method is affected by the statistical artefact of ‘regression towards the mean’. I identify several cases where this artefact may have affected particular conclusions about the PoIE, and relate these to the historical origins of ‘regression towards the (...) mean’. Although the conclusions of the recent report may not have been grossly affected, some of the inferential statistics were almost certainly biased by the methods used. I conclude that, unless such artefacts are fully dealt with in the future, and unless the statistical methods for assessing the PoIE evolve, strong evidence in support of the PoIE will remain lacking. (shrink)

Artificial stimulation of the peripheral vestibular system has been shown to improve ownership of body parts in neurological patients, suggesting vestibular contributions to bodily self-consciousness. Here, we investigated whether galvanic vestibular stimulation interferes with the mechanisms underlying ownership, touch, and the localization of one’s own hand in healthy participants by using the “rubber hand illusion” paradigm. Our results show that left anodal GVS increases illusory ownership of the fake hand and illusory location of touch. We propose that these changes are (...) due to vestibular interference with spatial and/or temporal mechanisms of visual-tactile integration leading to an enhancement of visual capture. As only left anodal GVS lead to such changes, and based on neurological data on body part ownership, we suggest that this vestibular interference is mediated by the right temporo-parietal junction and the posterior insula. (shrink)

Emerging evidence is now challenging the view that patients diagnosed with schizophrenia experience a selective deficit in their sense of agency. Additional disturbances seem to exist in their sense of body ownership. However, the factors underlying this disturbance in body ownership remain elusive. Knowledge of these factors, and increased understanding of how body ownership is related to other abnormalities seen in schizophrenia, could ultimately advance development of new treatments. Research on body ownership in schizophrenia has mainly been investigated with the (...) rubber hand illusion (RHI). Schizophrenia patients show higher susceptibility to the RHI, which may be explained by a stronger reliance on multisensory information over weaker stored body representations. This review shows that a coherent sense of body ownership arises from the integration of both bottom-up sensory processes and higher order, top-down bodily- and perceptual representations. Multisensory integration, temporal binding, anticipation, intention and efferent signals all partly modulate the complex experience of body ownership. Specifically, we propose that patients with schizophrenia have weaker stored body representations, and rely to a greater extent on external stimuli, such as visual information, due to imprecise or highly variable internal predictions on the consequences of action. Moreover, the reduced sense of agency in schizophrenia may additionally contribute to the disturbed sense of body ownership, as evidence from healthy participants suggests that agency and body ownership are interrelated. Vice versa, a reduced sense of body ownership may also contribute to a reduced sense of agency. Future studies should explicitly target the precise relation between the two in schizophrenia. (shrink)

Multisensory stimulation has been shown to alter the sense of body-ownership. Given that perceived similarity between one’s own body and those of others is crucial for social cognition, we investigated whether multisensory stimulation can lead participants to experience ownership over a hand of different skin colour. Results from two studies using introspective, behavioural and physiological methods show that, following synchronous visuotactile stimulation, participants can experience body-ownership over hands that seem to belong to a different racial group. Interestingly, a baseline measure (...) of implicit racial bias did not predict whether participants would experience the RHI, but the overall strength of experienced body-ownership seemed to predict the participants’ post-illusion implicit racial bias with those who experienced a stronger RHI showing a lower bias. These findings suggest that multisensory experiences can override strict ingroup/outgroup distinctions based on skin colour and point to a key role for sensory processing in social cognition. (shrink)

Multisensory stimulation has been shown to alter the sense of body-ownership. Given that perceived similarity between one’s own body and those of others is crucial for social cognition, we investigated whether multisensory stimulation can lead participants to experience ownership over a hand of different skin colour. Results from two studies using introspective, behavioural and physiological methods show that, following synchronous visuotactile stimulation, participants can experience body-ownership over hands that seem to belong to a different racial group. Interestingly, a baseline measure (...) of implicit racial bias did not predict whether participants would experience the RHI, but the overall strength of experienced body-ownership seemed to predict the participants’ post-illusion implicit racial bias with those who experienced a stronger RHI showing a lower bias. These findings suggest that multisensory experiences can override strict ingroup/outgroup distinctions based on skin colour and point to a key role for sensory processing in social cognition. (shrink)

There are two main pathways to investigate the sense of body ownership, (i) through the study of the conditions of embodiment for an object to be experienced as one's own and (ii) through the analysis of the deficits in patients who experience a body part as alien. Here, I propose that E is embodied if some properties of E are processed in the same way as the properties of one's body. However, one must distinguish among different types of embodiment, and (...) only self-specific embodiment can lead to feelings of ownership. I address issues such as the functional role and the dynamics of embodiment, degrees and measures of ownership, and shared body representations between self and others. I then analyse the interaction between ownership and disownership. On the one hand, I show that there is no evidence that in the Rubber Hand Illusion, the rubber hand replaces the biological hand. On the other hand, I argue that the sense of disownership experienced by patients towards their body part cannot be reduced to the mere lack of ownership. (shrink)

Visual, somatosensory, and perspectival cues normally provide congruent information about where the self is experienced. Separating those cues by virtual reality techniques, recent studies found that self-location was systematically biased to where a visual–tactile event was seen. Here we developed a novel, repeatable and implicit measure of self-location to compare and extend previous protocols. We investigated illusory self-location and associated phenomenological aspects in a lying body position that facilitates clinically observed abnormal self-location . The results confirm that the self is (...) located to where touch is seen. This leads to either predictable lowering or elevation of self-localization, and the latter was accompanied by sensations of floating, as during out-of-body experiences. Using a novel measurement we show that the unitary and localized character of the self can be experimentally separated from both the origin of the visual perspective and the location of the seen body, which is compatible with clinical data. (shrink)

When participants observed a rubber hand being touched, their sense of touch was activated . While this illusion might be caused by multi-modal integration, it may also be related to empathic function, which enables us to simulate the observed information. We examined individual differences in the RHI, including empathic and schizotypal personality traits, as previous research had suggested that schizophrenic patients would be more subject to the RHI. The results indicated that people who experience a stronger RHI might have stronger (...) empathic and schizotypal personalites simultaneously. We discussed these relationships in terms of self-other representations. (shrink)

How do we acquire a mental representation of our own face? Recently, synchronous, but not asynchronous, interpersonal multisensory stimulation between one’s own and another person’s face has been used to evoke changes in self-identification . We investigated the conscious experience of these changes with principal component analyses that revealed that while the conscious experience during synchronous IMS focused on resemblance and similarity with the other’s face, during asynchronous IMS it focused on multisensory stimulation. Analyses of the identified common factor structure (...) revealed significant quantitative differences between synchronous and asynchronous IMS on self-identification and perceived similarity with the other’s face. Experiment 2 revealed that participants with lower interoceptive sensitivity experienced stronger enfacement illusion. Overall, self-identification and body-ownership rely on similar basic mechanisms of multisensory integration, but the effects of multisensory input on their experience are qualitatively different, possibly underlying the face’s unique role as a marker of selfhood. (shrink)

The nonvisual self-touch rubber hand paradigm elicits the compelling illusion that one is touching one’s own hand even though the two hands are not in contact. In four experiments, we investigated spatial limits of distance and alignment on the nonvisual self-touch illusion and the well-known visual rubber hand illusion. Common procedures and common assessment methods were used. Subjective experience of the illusion was assessed by agreement ratings for statements on a questionnaire and time of illusion onset. The nonvisual self-touch illusion (...) was diminished though never abolished by distance and alignment manipulations, whereas the visual rubber hand illusion was more robust against these manipulations. We assessed proprioceptive drift, and implications of a double dissociation between subjective experience of the illusion and proprioceptive drift are discussed. (shrink)