Which is my body and how do I distinguish it from the bodies of others, or from objects in the surrounding environment? The perception of our own body and more particularly our sense of body ownership is taken for granted. Nevertheless experimental findings from body ownership illusions (BOIs), show that under specific multisensory conditions, we can experience artificial body parts or fake bodies as our own body parts or body respectively. (...) The aim of the present paper is to discuss how and why BOIs are induced. We review several experimental findings concerning the spatial, temporal and semantic principles of crossmodal stimuli that have been applied to induce BOIs. On the basis of these principles, we discuss theoretical approaches concerning the underlying mechanism of BOIs. We propose a conceptualization based on Bayesian causal inference for addressing how our nervous system could infer whether an object belongs to our own body, using multisensory, sensorimotor and semantic information, and we discuss how this can account for several experimental findings. Finally, we point to neural network models as an implementational framework within which the computational problem behind BOIs could be addressed in the future. (shrink)

We investigate two issues about the subjective experience of one's body: first, is the experience of owning a full-body fundamentally different from the experience of owning a body-part?Second, when I experience a bodily sensation, does it guarantee that I cannot be wrong about whether it is me who feels it? To address these issues, we conducted a series of experiments that combined the rubber hand illusion (RHI) and the “body swap illusion.” The subject wore a head (...) mounted display (HMD) connected with a stereo camera set on the experimenter's head. Sitting face to face, they used their right hand holding a paintbrush to brush each other's left hand. Through the HMD, the subject adopted the experimenter's first-person perspective (1PP) as if it was his/her own 1PP: the subject watched either the experimenter's hand from the adopted 1PP, and/or the subject's own hand from the adopted third-person perspective (3PP) in the opposite direction (180°), or the subject's full body from the adopted 3PP (180°, with or without face). The synchronous full-body conditions generate a “self-touching illusion”: many participants felt that “I was brushing my own hand!” We found that (1) the sense of body-part ownership and the sense of full-body ownership are not fundamentally different from each other; and (2) our data present a strong case against the mainstream philosophical view called the immunity principle (IEM). We argue that it is possible for misrepresentation to occur in the subject's sense of “experiential ownership” (the sense that I am the one who is having this bodily experience). We discuss these findings and conclude that not only the sense of body ownership but also the sense of experiential ownership call for further interdisciplinary studies. (shrink)

Recent studies of the rubber hand illusion (RHI) have shown that the sense of body ownership is constrained by several factors and yet is still very flexible. However, exactly how flexible is our sense of body ownership? In this study, we address this issue by investigating the following question: is it possible that one may have the illusory experience of owning four hands? Under visual manipulation, the participant adopted the experimenter’s first-person perspective (1PP) as if it (...) was his/her own. Sitting face to face, the participant saw four hands—the experimenter’s two hands from the adopted 1PP together with the subject’s own two hands from the adopted third-person perspective (3PP). We found that: (1) the four-hand illusion did not occur in the passive four-hand condition. (2) In the active four-hand condition, the participants tapped their index fingers, imitated by the experimenter. When tactile stimulations were not provided, the key illusion was not induced, either. (3) Strikingly, once all four hands began to act with the same pattern and received synchronous tactile stimulations at the same time, many participants felt as if they had two more hands. These results show that the sense of body ownership is much more flexible than most researchers have suggested. (shrink)

This paper analyzes in the use of virtual reality when used to induce full-body ownership in violent offenders in order to elicit empathetic feelings by allowing them to embody the virtual body of a victim of domestic abuse. The authors explore potentially harmful effects to individuals participating in this kind of therapy and question whether consent is fully informed. The paper concludes with guidelines for ethical research and rehabilitation using this innovative technology.

Body ownership concerns what it is like to feel a body part or a full body as mine, and has become a prominent area of study. We propose that there is a closely related type of bodily self-consciousness largely neglected by researchers—experiential ownership. It refers to the sense that I am the one who is having a conscious experience. Are body ownership and experiential ownership actually the same phenomenon or are they genuinely (...) different? In our experiments, the participant watched a rubber hand or someone else’s body from the first-person perspective and was touched either synchronously or asynchronously. The main findings: (1) The sense of body ownership was hindered in the asynchronous conditions of both the body-part and the full-body experiments. However, a strong sense of experiential ownership was observed in those conditions. (2) We found the opposite when the participants’ responses were measured after tactile stimulations had ceased for 5 s. In the synchronous conditions of another set of body-part and full-body experiments, only experiential ownership was blocked but not body ownership. These results demonstrate for the first time the double dissociation between body ownership and experiential ownership. Experiential ownership is indeed a distinct type of bodily self-consciousness. (shrink)

Manipulating sensory and motor cues can cause an illusionary perception of ownership of a fake body part. Presumably, the illusion can work as long as the false body part’s position and appearance are anatomically plausible. Here, we introduce an illusion that challenges past assumptions on body ownership. We used virtual reality to switch and mirror participants’ views of their hands. When a participant moves their physical hand, they see the incongruent virtual hand moving. The result (...) is an anatomically implausible configuration of the fake hand. Despite the hand switch, participants reported significant body ownership sensations over the virtual hands. In the first between-group experiment, we found that the strength of body ownership over the incongruent hands was similar to that of congruent hands. Whereas, in the second within-group experiment, anatomical incongruency significantly decreased body ownership. Still, participants reported significant body ownership sensations of the switched hands. Curiously, we found that perceived levels of agency mediate the effect of anatomical congruency on body ownership. These findings offer a fresh perspective on the relationship between anatomical plausibility and assumed body ownership. We propose that goal-directed and purposeful actions can override anatomical plausibility constraints and discuss this in the context of the immersive properties of virtual reality. (shrink)

When subjects view stimulation of a rubber hand while feeling congruent stimulation of their own hand, they may come to feel that the rubber hand is part of their own body. This illusion of body ownership is termed ‘Rubber Hand Illusion’ . We investigated sensitivity of RHI to spatial mismatches between visual and somatic experience. We compared the effects of spatial mismatch between the stimulation of the two hands, and equivalent mismatches between the postures of the two (...) hands. We created the mismatch either by adjusting stimulation or posture of the subject’s hand, or, in a separate group of subjects, by adjusting stimulation or posture of the rubber hand. The matching processes underlying body ownership were asymmetrical. The illusion survived small changes in the subject’s hand posture, but disappeared when the same posture transformations were applied to the rubber hand. Mismatch between the stimulation delivered to the subject’s hand and the rubber hand abolished the illusion. The combination of these two situations is of particular interest. When the subject’s hand posture was slightly different from the rubber hand posture, the RHI remained as long as stimulation of the two hands was congruent in a hand-centred spatial reference frame, even though the altered posture of the subject’s hand meant that stimulation was incongruent in external space. Conversely, the RHI was reduced when the stimulation was incongruent in hand-centred space but congruent in external space. We conclude that the visual–tactile correlation that causes the RHI is computed within a hand-centred frame of reference, which is updated with changes in body posture. Current sensory evidence about what is ‘me’ is interpreted with respect to a prior mental body representation. (shrink)

Objects which a human agent controls by efferent activities can be perceived by the agent as belonging to his or her body. This suggests that what an agent counts as “body” is plastic, depending on what she or he controls. Yet there are possible limitations for such momentary plasticity. One of these limitations is that sensations stemming from the body and sensations stemming from objects outside the body are not integrated if they do not sufficiently “match”. (...) What “matches” and what does not is conceivably determined by long–term experience with the perceptual changes that body movements typically produce. Children have accumulated less sensorimotor experience than adults have. Consequently, they express higher flexibility to integrate body-internal and body-external signals, independent of their “match” as suggested by rubber hand illusion studies. However, children’s motor performance in tool use is more affected by mismatching body-internal and body-external action effects than that of adults, possibly because of less developed means to overcome such mismatches. We review research on perception-action interactions, multisensory integration, and developmental psychology to build bridges between these research fields. By doing so, we account for the flexibility of the sense of body ownership for actively controlled events and its development through ontogeny. This gives us the opportunity to validate the suggested mechanisms for generating ownership by investigating their effects in still developing and incomplete stages in children. We suggest testable predictions for future studies investigating both body ownership and motor skills throughout the lifespan. (shrink)

This article examines the inflationary view of the body ownership. It reviews a growing body of empirical research on the sense of body ownership that suggests that the deflationary depends on the integration of somatosensory signals. It discusses the results of recent research on out-of-body experiences and shows that the neurocognitive processes involved in the Rubber Hand Illusion are also involved in OBE. It suggests that this experience of bodily ownership may be a (...) critical component of self-specificity. (shrink)

Our understanding of body ownership largely relies on the Rubber Hand Illusion (RHI) paradigm where synchronous stroking of the real and fake hands leads to an illusion of ownership of RH provided its physical, anatomical, and spatial plausibility. Self-attribution of a fake hand also occurs during visuomotor synchrony, when the visual feedback of self-initiated movements follows the trajectory of the instantiated motor command. In both cases, the experience of ownership is established through bottom-up integration and top-down (...) prediction of multisensory (proximodistal) cues within the peripersonal space. It seems, however, that depending on whether the signals are externally or self-generated, top-down expectation signals are qualitatively different. On the one hand, in RHI, the sensory correlations are modulated by empirically induced priors about the internal model of the body. On the other hand, in mRHI, body ownership is actively shaped by processes allowing for continuous comparison between the actual and predicted sensory consequences of the actions. Ample research demonstrates that the differential processing of the predicted and the actual reafferent information is addressed by the central nervous system via an internal Forward Model (FM). Indeed, results from mRHI suggest that in action-contexts mechanism underlying body ownership could be similar to the FM. Crucially FMs integrate across all sensory input including not only proximodistal (visuomotor) but also purely distal sensory signals (visuoauditory). Thus if body ownership results from a consistency of FM, it would be affected by the (in)congruency of purely distal signals provided that they inform about the action-consequences relevant to the task. Here we explicitly address this question. To test our hypothesis, we devise an embodied VR-based task where action outcomes were signaled by distinct auditory cues. By manipulating the cues with respect to their spatial, temporal and semantic congruency, we show that purely distal feedback violating predictions about action outcomes compromises both body ownership and performance. These results demonstrate that body ownership is influenced by cues which not only pertain to the body itself but also those arising outside of the body, and suggest that in goal-oriented tasks body ownership might result from the consistency of forward models. (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)

We investigated how motor agency in the voluntary control of body movement influences body awareness. In the Rubber Hand Illusion , synchronous tactile stimulation of a rubber hand and the participant’s hand leads to a feeling of the rubber hand being incorporated in the participant’s own body. One quantifiable behavioural correlate of the illusion is an induced shift in the perceived location of the participant’s hand towards the rubber hand. Previous studies showed that the induced changes in (...) body awareness are local and fragmented: the proprioceptive drift is largely restricted to the stimulated finger. In the present study, we investigated whether active and passive movements, rather than tactile stimulation, would lead to similarly fragmented body awareness. Participants watched a projected image of their hand under three conditions: active finger movement, passive finger movement, and tactile stimulation. Visual feedback was either synchronous or asynchronous with respect to stimulation of the hand. A significant overall RHI, defined as greater drifts following synchronous than asynchronous stimulation, was found in all cases. However, the distribution of the RHI across stimulated and non-stimulated fingers depended on the kind of stimulation. Localised proprioceptive drifts, specific to the stimulated finger, were found for tactile and passive stimulation. Conversely, during active movement of a single digit, the proprioceptive drifts were not localised to that digit, but were spread across the whole hand. Whereas a purely proprioceptive sense of body-ownership is local and fragmented, the motor sense of agency integrates distinct body-parts into a coherent, unified awareness of the body. (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)

We previously showed that the illusory sense of ownership and agency over a moving body in immersive virtual reality can trigger subjective and physiological reactions on the real subject’s body and, therefore, an acute improvement of cognitive functions after a single session of high-intensity intermittent exercise performed exclusively by one’s own virtual body, similar to what happens when we actually do physical activity. As well as confirming previous results, here, we aimed at finding in the elderly (...) an increased improvement after a longer virtual training with similar characteristics. Forty-two healthy older subjects completed a parallel-group randomized controlled trial including an adapted version of the virtual training previously used: while sitting, participants observed the virtual body in a first-person perspective or a third-person perspective performing 20 min of virtual high-intensity intermittent exercise. This was repeated twice a week for 6 weeks. During the vHIE, we measured the heart rate and administered questionnaires to evaluate illusory body ownership and agency. Before the beginning of the intervention, immediately after the first session of vHIE, and at the end of the entire intervention, we evaluated the cognitive performance at the Stroop task with online recording of the hemodynamic activity over the left dorsolateral prefrontal cortex. While we confirm previous results regarding the virtual illusion and its physiological effects, we did not find significant cognitive or neural improvement immediately after the first vHIE session. As a novelty, in the 1PP group only, we detected a significant decrease in the response time of the Stroop task in the post-intervention assessment compared to its baseline; coherently, we found an increased activation on left dorsolateral prefrontal cortex after the entire intervention. While the current results strengthen the impact of the virtual full-body illusion and its physiological consequences on the elderly as well, they might have stronger and more established body representations. Perhaps, a longer and increased exposure to those illusions is necessary to initiate the cascade of events that culminates to an improved cognitive performance. (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)

Open peer commentary on the article “The Plasticity of the Bodily Self: Head Movements in Bodily Illusions and Their Relation to Gallagher’s Body Image and Body Schema” by Marte Roel Lesur, Michael Gaebler, Philippe Bertrand & Bigna Lenggenhager.: In my commentary, I raise some questions about the applicability of Gallagher’s distinction between body image and body schema to the experimental research reported and discussed in the target article. I suggest that the distinction between body (...) image and body schema is of limited help in this context, and that Gallagher’s distinction between sense of ownership and sense of agency provides a more natural and fruitful theoretical framework to discuss that research. (shrink)

Previous studies on body ownership illusions have shown that under certain multimodal conditions, healthy people can experience artificial body-parts as if they were part of their own body, with direct physiological consequences for the real limb that gets ‘substituted’. In this study we wanted to assess (a) whether healthy people can experience ‘missing’ a body-part through illusory ownership of an amputated virtual body, and (b) whether this would cause corticospinal excitability changes in (...) muscles associated with the ‘missing’ body-part. Forty right-handed participants saw a virtual body from a first person perspective but for half of them the virtual body was missing a part of its right arm. Single pulse transcranial magnetic stimulation was applied before and after the experiment to left and right motor cortices. Motor evoked potentials (MEPs) were recorded from the first dorsal interosseous (FDI) and the extensor digitorum communis (EDC) of each hand. We found that the stronger the illusion of amputation and arm ownership, the more the reduction of MEP amplitudes of the EDC muscle for the contralateral sensorimotor cortex. In contrast, no association was found for the EDC amplitudes in the ipsilateral cortex and for the FDI amplitudes in both contralateral and ipsilateral cortices. Our study provides evidence that a short-term illusory perception of missing a body-part can trigger inhibitory effects on corticospinal pathways and importantly in the absence of any limb deafferentation or disuse. (shrink)

In a recent study (Chen et al., 2018), we conducted a series of experiments that induced the “four-hand illusion”: using a head-mounted display (HMD), the participant adopted the experimenter’s first-person perspective (1PP) as if it was his/her own 1PP. The participant saw four hands via the HMD: the experimenter’s two hands from the adopted 1PP and the subject’s own two hands from the adopted third-person perspective (3PP). In the active four-hand condition, the participant tapped his/her index fingers, imitated by the (...) experimenter. Once all four hands acted synchronously and received synchronous tactile stimulations at the same time, many participants felt as if they owned two more hands. In this paper, we argue that there is a philosophical implication of this novel illusion. According to Merleau-Ponty (1945/1962) and Legrand (2010), one can experience one’s own body or body-part either as-object or as-subject but cannot experience it as both simultaneously, i.e., these two experiences are mutually exclusive. Call this view the Experiential Exclusion Thesis. We contend that a key component of the four-hand illusion—the subjective experience of the 1PP-hands that involved both “kinesthetic sense of movement” and “visual sense of movement” (the movement that the participant sees via the HMD)—provides an important counter-example against this thesis. We argue that it is possible for a healthy subject to experience the same body-part both as-subject and as-object simultaneously. Our goal is not to annihilate the distinction between body-as-object and body-as-subject, but to show that it is not as rigid as suggested by the phenomenologists. (shrink)

The rubber hand illusion is one of the most commonly used paradigms to examine the sense of body ownership. Touches are synchronously applied to the real hand, hidden from view, and a false hand in an anatomically congruent position. During the illusion one may perceive that the feeling of touch arises from the false hand, and that the false hand is one's own. The relationship between referral of touch and body ownership in the illusion is unclear, (...) and some articles average responses to statements addressing these experiences, which may be inappropriate depending on the research question of interest. To address these concerns, we re-analyzed three freely available datasets to better understand the relationship between referral of touch and feeling of ownership in the RHI. We found that most participants who report a feeling of ownership also report referral of touch, and that referral of touch and ownership show a moderately strong positive relationship that was highly replicable. In addition, referral of touch tends to be reported more strongly and more frequently than the feeling of ownership over the hand. The former observations confirm that referral of touch and ownership are related experiences in the RHI. The latter, however, indicate that when pooling the statements one may obtain a higher number of illusion ‘responders’ compared to considering the ownership statements in isolation. These results have implications for the RHI as an experimental paradigm. (shrink)

Abstract: What grounds the experience of our body as our own? Can we rationally doubt that this is our own body when we feel sensations in it? This article shows how recent empirical evidence can shed light on issues on the body and the self, such as the grounds of the sense of body ownership and the immunity to error through misidentification of bodily self-ascriptions. In particular, it discusses how bodily illusions (e.g., the Rubber (...) Hand Illusion), bodily disruptions (e.g., somatoparaphrenia), and the multimodal nature of bodily self-knowledge challenge a classic view of ownership and immunity that puts bodily sensations at its core. (shrink)

_Riassunto_: Il concetto di modello corporeo è un’acquisizione relativamente recente della neuropsicologia. Studiosi attivi in questo ambito di ricerca interpretano il concetto di modello corporeo come facente riferimento ad un modello interno, una rappresentazione cognitiva delle proprietà anatomiche, volumetriche e posturali del corpo umano. È stato dimostrato come il modello corporeo fornisca un _background_ cognitivo stabile a processi d’integrazione dell’informazione multisensoriale riferita al corpo proprio. In questo senso, si ritiene che esso concorra a generare una forma elementare di autocoscienza corporea, (...) il cosiddetto sé corporeo minimale. Il presente contributo intende fornire un’aggiornata rassegna tematica sul modello corporeo trattato contestualmente alla teoria neuropsicologica del sé corporeo minimale. A tale scopo, saranno discussi studi teorici di rilievo che condividono una comune base sperimentale: le _Illusioni della Proprietà Corporea_ (IPC). Attenzione verrà riservata anche alle principali ricadute che un tale lavoro di sistematizzazione teorica ha recentemente conosciuto in psicopatologia, filosofia della neuroscienza e neurofilosofia. Saranno infine segnalati alcuni problemi aperti nella contemporanea ricerca sul modello corporeo. _Parole chiave_: Neuropsicologia; Modello corporeo; Sé corporeo minimo; Illusioni della proprietà corporea _The body model and the neuropsychological theory of the minimal bodily self. A thematic revie _ _Abstract_: The body model is a relatively new concept developed by neuropsychologists that refers to an internal model or cognitive representation of the anatomical, volumetric, and structural aspects of the human body. The body model has been shown to provide a stable cognitive background for body-related multisensory integration, thereby contributing to the formation of an elementary kind of corporeal self-consciousness, the so-called minimal bodily self. Here, I provide an updated thematic review of research on the body model in the context of the neuropsychological theory of the minimal bodily self. It examines theoretical studies based on experiments on _Body Ownership Illusions_ (BOI) and the important implications this work has for psychopathology, the philosophy of neuroscience and neurophilosophy. Finally, it points to some unanswered questions in contemporary research on the body model. _Keywords_: Neuropsychology;_ _Body Model; Minimal Bodily Self; Body Ownership Illusions. (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)

In recent years, a debate has emerged on whether bodily sensations are typically accompanied by a sense of body ownership, namely a distinctive experience of one's body or body part as one's own. Realists about the sense of body ownership heavily rely on evidence from experimentally-induced bodily illusions (e.g., the rubber hand illusion) and pathological disownership syndromes (e.g. somatoparaphrenia). In this chapter, I will introduce novel evidence regarding body disownership syndromes induced by (...) psychoactive drugs rather than pathological conditions, and discuss its relevance to the debate on the sense of body ownership. (shrink)

In this article, we explore the effect of a modification of one aspect of body awareness, the so-called sense of body-ownership, on pain perception. In order to do so, we modify body-ownership in healthy participants by using a visuo-tactile illusion called the 'rubber hand illusion'.We combine the classical experimental paradigm of the RHI with a method to induce pain by thermal stimulation. We present and discuss two experiments that show interesting but conflicting results. In the (...) first experiment our results show the RHI has the effect of decreasing pain estimations, whereas in the second experiment the RHI has the effect of increasing pain estimations. We discuss the different factors that could be involved in this difference, and suggest that different types of changes in participants' body schema might have been involved in the two experiments. We propose that an approach that considers participants' subjective experience of the illusion will help us to solve this puzzle. (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)

This paper presents a gamified motor imagery brain-computer interface (MI-BCI) training in immersive virtual reality. Aim of the proposed training method is to increase engagement, attention, and motivation in co-adaptive event-driven MI-BCI training. This was achieved using gamification, progressive increase of the training pace, and virtual reality design reinforcing the body ownership transfer (embodiment) into the avatar. From the 20 healthy participants performing 6 runs of 2-class MI-BCI training (left/right hand), 19 were trained for a basic level of (...) MI-BCI operation, with average peak accuracy in the session equal to 75.84\%. This confirms the proposed training method succeeded in improvement of the MI-BCI skills; moreover, participants were leaving the session in high positive affect. Although the performance was not directly correlated to the degree of embodiment, subjective magnitude of the body ownership transfer illusion correlated with the abilities to modulate the sensorimotor rhythm. (shrink)

Our own body seems to be the object that we know the best for we constantly receive a flow of internal information about it. Yet bodily awareness has attracted little attention in the literature, possibly because it seems reducible to William James’s description of a “feeling of the same old body always there” (1890, p. 242). But it is not true that our body always feels so familiar. In particular, puzzling neurological disorders and new bodily illusions (...) raise a wide range of questions about the relationship between the body and the self. Although most of the time we experience our body as our own, it is possible to report feeling parts of our body as alien. It is also possible to experience extraneous objects, such as prosthetic hands, as our own. Hence, what makes us feel this particular body as our own? The fact that we feel sensations there? The fact that we can voluntarily move it? Or the fact that it needs protection for self-preservation? To answer these questions, we need a better understanding of the various aspects of bodily self-awareness, including the spatiality of bodily sensations, their multimodality, their role in social cognition, their relation to action, and to self-defence. Mind the Body thus provides a comprehensive treatment of bodily awareness and of the sense of bodily ownership, combining philosophical analysis with recent experimental results from cognitive science. (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)

Self-location—the sense of where I am in space—provides an experiential anchor for one's interaction with the environment. In the studies of full-body illusions, many researchers have defined self-location solely in terms of body-location—the subjective feeling of where my body is. Although this view is useful, there is an issue regarding whether it can fully accommodate the role of 1PP-location—the sense of where my first-person perspective is located in space. In this study, we investigate self-location by comparing (...) body-location and 1PP-location: using a head-mounted display (HMD) and a stereo camera, the subjects watched their own body standing in front of them and received tactile stimulations. We manipulated their senses of body-location and 1PP-location in three different conditions: the participants standing still (Basic condition), asking them to move forward (Walking condition), and swiftly moving the stereo camera away from their body (Visual condition). In the Walking condition, the participants watched their body moving away from their 1PP. In the Visual condition, the scene seen via the HMD was systematically receding. Our data show that, under different manipulations of movement, the spatial unity between 1PP-location and body-location can be temporarily interrupted. Interestingly, we also observed a “double-body effect.” We further suggest that it is better to consider body-location and 1PP-location as interrelated but distinct factors that jointly support the sense of self-location. (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)

In lieu of an abstract, here is a brief excerpt of the content:Philosophy, Psychiatry, & Psychology 9.1 (2002) 41-46 [Access article in PDF] On What There Really Is to Our Notion of Ownership of a Thought Annalisa Coliva JOHN CAMPBELL'S REPLY to my paper aims at reestablishing the point that there are two strands to our notion of ownership of a thought. There are two ways of cashing out this idea. 1 First, one could say that A is (...) the owner of a thought if and only if both the following two independent conditions apply 2 : (1) X is introspectively aware of a token thought and (2) X is the person who formed that token thought. Second, one may hold that there are twodifferent and independent notions of ownership of a thought, call it O1 and O2, corresponding to (1) and (2), respectively. For brevity, I will refer only to the first interpretation. But what I will be saying will apply, mutatis mutandis, to both.On this view, thought insertion would be a case in which someone thinks that (1) is satisfied, while (2) is not and, therefore, denies that the thought she is introspectively aware of is her own. 3 Campbell's explanation of thought insertion is quite clear: the subject has prima facie reasons to think that she is not the person who formed that token thought—maybe because she does not experience that thought as formed by herself—and, therefore, has prima facie reasons to deny that she is its owner, but she is mistaken in identifying the producer of the thought and what she says is false, yet reasonable. 4 Notice, however, an important consequence of Campbell's model. If (1) and (2) are independent conditions, then one could obtain without the other. Hence, it must be conceivable that one is introspectively aware of a thought that one has not produced. Indeed, cases of multiple personality, if taken literally, might be taken as examples of this kind of situation: person A and person B inhabit the same body, A can have access to B's thoughts, yet B remains their producer. So A could actually say something like "I'm thinking (i.e. I am immediately aware) that p, but this is not my thought (it is not the thought I produced), it's B's (the thought that B produced)" and what she would be saying would in fact be true.Yet, a simple-minded reaction one may have toward this line of explanation is this: If the subject is either saying something false, but reasonable, or, indeed, something altogether true, when she says "I'm thinking 'Kill God,' but this isn't my thought, it's Chris'," why should we consider her report as an expression of some kind of cognitive illusion, 5 which we take as a symptom of mental illness, as opposed to, at most, a possible mistake in identifying the producer of the thought? And, connectedly, why should we try to cure her, rather than just, at most, correct her? [End Page 41]Hence, the whole dispute between Campbell and me hinges on whether it is logically possible for one to be introspectively aware of a thought and yet not be its producer. Campbell claims that it is, whereas I deny that this is a genuine possibility. He holds that these are two independent conditions and that the one can obtain without the other, whereas I hold that they are not independent and that they stand or fall together. Campbell is fully aware of being making a surprising claim because, as he points out, "[The two strands in the ordinary notion of ownership of a thought] do not ordinarily even seem to come apart" (Campbell 2002, italics mine). Yet he offers in its support no more than an analogy between being the person who produced a certain signature and being the person who produced a given token thought. Let us look at it closer.Consider the following situation: a person NN looks at a piece of paper with NN written on it and wonders whether she is the... (shrink)

On the one hand, it is often assumed that the Rubber Hand Illusion (RHI) is constrained by a structural body model so that one cannot implement supernumerary limbs. On the other hand, several recent studies reported illusory duplication of the right hand in subjects exposed to two adjacent rubber hands. The present study tested whether spatial constraints may affect the possibility of inducing the sense of ownership to two rubber hands located side by side to the left of (...) the subject's hand. We found that only the closest rubber hand appeared both objectively (proprioceptive drift) and subjectively (ownership rating) embodied. Crucially, synchronous touch of a second, but farther, rubber hand disrupted the objective measure of the RHI, but not the subjective one. We concluded that, in order to elicit a genuine RHI for multiple rubber hands, the two rubber hands must be at the same distance from the subject's hand/body. (shrink)

Monique Wittig's The Lesbian Body subverts the authority of the anatomy teaching text, and challenges its claim to objectivity, by writing to the texts of Andreas Vesalius. Vesalius, working in the late 15th century, is recognized as having set the precedent for how the anatomy of the human body is taught even today. By writing a ‘lesbian body’ in disarray, Wittig metaphorically topples the authority and order of the standard Vesalian anatomy. By writing that body as (...) a desiring subject, she also invites us to question the desire for knowledge and ownership of that knowledge, and the illusion of scientific objectivity. Indeed, she offers us a celebration of the subjectivity of the production of texts and identities. But in her rewriting, she must also adopt a particular subject position and guard that position from the ‘wrong’ interpretations. The Lesbian Body is then, despite its literary and political force, a text which fears the interpretive role of its reader. (shrink)

Inducing the rubber hand illusion (RHI) requires that participants look at an imitation hand while it is stroked in synchrony with their occluded biological hand. Previous explanations of the RHI have emphasized multisensory integration, and excluded higher cognitive functions. We investigated the relationship between the RHI and higher cognitive functions by experimentally testing task switch (as measured by switch cost) and mind wandering (as measured by SART score); we also included a questionnaire for attentional control that comprises two subscales, attention-shift (...) and attention-focus. To assess experience of RHI, the Botvinick and Cohen (1998) questionnaire was used and illusion onset time was recorded. Our results indicate that rapidity of onset reliably indicates illusion strength. Regression analysis revealed that participants evincing less switch cost and higher attention-shift scores had faster RHI onset times, and that those with higher attention-shift scores experienced the RHI more vividly. These results suggest that the multi-sensory hypothesis is not sufficient to explain the illusion: higher cognitive functions should be taken into account when explaining variation in the experience of ownership for the rubber hand. (shrink)

To offer engaging neurorehabilitation training to neurologic patients, motor tasks are often visualized in virtual reality. Recently introduced head-mounted displays allow to realistically mimic the body of the user from a first-person perspective in a highly immersive VR environment. In this immersive environment, users may embody avatars with different body characteristics. Importantly, body characteristics impact how people perform actions. Therefore, alternating body perceptions using immersive VR may be a powerful tool to promote motor activity in neurologic (...) patients. However, the ability of the brain to adapt motor commands based on a perceived modified reality has not yet been fully explored. To fill this gap, we “tricked the brain” using immersive VR and investigated if multisensory feedback modulating the physical properties of an embodied avatar influences motor brain networks and control. Ten healthy participants were immersed in a virtual environment using an HMD, where they saw an avatar from first-person perspective. We slowly transformed the surface of the avatar from human to stone. We enforced this visual change by repetitively touching the real arm of the participant and the arm of the avatar with a hammer, while progressively replacing the sound of the hammer against skin with stone hitting sound via loudspeaker. We applied single-pulse transcranial magnetic simulation to evaluate changes in motor cortical excitability associated with the illusion. Further, to investigate if the “stone illusion” affected motor control, participants performed a reaching task with the human and stone avatar. Questionnaires assessed the subjectively reported strength of embodiment and illusion. Our results show that participants experienced the “stone arm illusion.” Particularly, they rated their arm as heavier, colder, stiffer, and more insensitive when immersed with the stone than human avatar, without the illusion affecting their experienced feeling of body ownership. Further, the reported illusion strength was associated with enhanced motor cortical excitability and faster movement initiations, indicating that participants may have physically mirrored and compensated for the embodied body characteristics of the stone avatar. Together, immersive VR has the potential to influence motor brain networks by subtly modifying the perception of reality, opening new perspectives for the motor recovery of patients. (shrink)

The distinction between the first-person perspective (1PP) and the third-person perspective (3PP) has been widely regarded as fundamental and rigid, and many researchers hold that genuine bodily illusions can only be experienced from the 1PP. We applied VR technology to investigate whether this mainstream view is correct. In our experiments, the participants were immersed in a VR environment in which they saw a life-sized virtual body either from the 1PP or from the 3PP. They either passively received tactile (...) stimulations and/or actively interacted with a virtual soccer ball. Our VR system created novel visuo-motor-tactile correlations between the real and the virtual world: when the participant interacted with a real plastic soccer ball, he/she would feel corresponding tactile sensations and see the avatar performing the exact same movements. We found that a clear sense of ownership over the avatar was induced not only in the 1PP condition but also in the Passive-3PP and the Active-3PP conditions. We also observed evidence suggesting that it is possible to experience one’s body-location, 1PP-location, as well as self-location, both from the 1PP and from the 3PP. Together, we demonstrate that there is in fact no fundamental gap between embodied 1PP and embodied 3PP in the virtual world. (shrink)

Lee and Schwartz procedures of separation offer a much needed interpretation of the literature on moral cleansing. However, body ownership as a grounded mechanism of separation and connection has been neglected. We argue that embodiment may be employed to connect the self to desirable aspects of cognitive and emotional interactions and disembodiment to disconnect from undesirable elements.

The recent distinction between sense of agency and sense of body-ownership has attracted considerable empirical and theoretical interest. The respective contributions of central motor signals and peripheral afferent signals to these two varieties of body experience remain unknown. In the present review, we consider the methodological problems encountered in the empirical study of agency and body-ownership, and we then present a series of experiments that study the interplay between motor and sensory information. In particular, we (...) focus on how multisensory signals interact with body representations to generate the sense of body-ownership, and how the sense of agency modulates the sense of body-ownership. Finally, we consider the respective roles of efferent and afferent signals for the experience of one’s own body and actions, in relation to self-recognition and the recognition of other people’s actions. We suggest that the coherent experience of the body depends on the integration of efferent information with afferent information in action contexts. Overall, whereas afferent signals provide the distinctive content of one’s own body experience, efferent signals seem to structure the experience of one’s own body in an integrative and coherent way. (shrink)