There is a debate between David Barnett and Rory Madden concerning the features that “our naïve conception of conscious subjects” has. While Barnett claims that our conception demands that conscious subjects be simple, Madden holds that our conception demands that conscious beings be topologically integrated. In this paper, I aim to bring some empirical results concerning the rubber-hand illusions and bilocation illusions to bear on this topic. While I do not reach a definitive resolution to the dispute between Barnett and (...) Madden, I suggest that, provisionally, the empirical results favor Barnett’s proposal. (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)

What grounds my experience of my body as my own? The body that one experiences is always one’s own, but it does not follow that one always experiences it as one’s own. One might even feel that a body part does not belong to oneself despite feeling sensations in it, like in asomatognosia. The article aims at understanding the link between bodily sensations and the sense of ownership by investigating the role played by the body schema.

The brain represents the body in different ways for different purposes. Several concepts and even more numerous labels have historically been proposed to define these representations in operational terms. Recent evidence of embodiment of external objects has added complexity to an already quite intricate picture. In particular, because of their perceptual and motor effects, both rubber hands and tools can be conceived as embodied, that is, represented in the brain as if they were parts of one's own body. But are (...) there any limits to what we can embody? What constraints lay upon embodiment? And are they similar both for motor embodiment and for perceptual embodiment? Here, we consider the implications emerging from the different, and up-to-now relatively separate research domains of tool use and rubber hand illusion for understanding the rules of embodiment. In particular, we compare what the embodiment of tools and prostheses may or may not have in common. We conclude that in both cases, although for different reasons and with different constraints, embodiment is only partial. (shrink)

I introduce and defend the notion of a cognitive account of the sense of ownership. A cognitive account of the sense of ownership holds that one experiences something as one's own only if one thinks of something as one's own. By contrast, a phenomenal account of the sense of ownership holds that one can experience something as one's own without thinking about anything as one's own. I argue that we have no reason to favour phenomenal accounts over cognitive accounts, that (...) cognitive accounts are plausible given that much of our mental activity has unnoticed effects on our mental life, and that certain illusory experiences of body ownership sometimes described as thought-independent may be best explained as imaginative perceptual experiences. (shrink)

Since Aristotle, touch has been found especially hard to define. One of the few unchallenged intuition about touch, however, is that tactile awareness entertains some especially close relationship with bodily awareness. This article considers the relation between touch and bodily awareness from two different perspectives: the body template theory and the body map theory. According to the former, touch is defined by the fact that tactile content matches proprioceptive content. We raise some objections against such a bodily definition of touch (...) and suggest, as an alternative, to revive the proposal according to which touch is essentially a sense of pressure. According to the body map theory, tactile sensations are localized within the frame of reference provided by the mental representation of the space of the body. We argue that this approach of the location of bodily sensations fares better that the Local Sign theory that denies intrinsic spatiality to touch. (shrink)

In rubber hand illusions and full body illusions, touch sensations are projected to non-body objects such as rubber hands, dolls or virtual bodies. The robustness, limits and further perceptual consequences of such illusions are not yet fully explored or understood. A number of experiments are reported that test the limits of a variant of the rubber hand illusion. Methodology/Principal Findings -/- A variant of the rubber hand illusion is explored, in which the real and foreign hands are aligned in personal (...) space. The presence of the illusion is ascertained with participants' scores and temperature changes of the real arm. This generates a basic illusion of touch projected to a foreign arm. Participants are presented with further, unusual visuotactile stimuli subsequent to onset of the basic illusion. Such further visuotactile stimulation is found to generate very unusual experiences of supernatural touch and touch on a non-hand object. The finding of touch on a non-hand object conflicts with prior findings, and to resolve this conflict a further hypothesis is successfully tested: that without prior onset of the basic illusion this unusual experience does not occur. Conclusions/Significance -/- A rubber hand illusion is found that can arise when the real and the foreign arm are aligned in personal space. This illusion persists through periods of no tactile stimulation and is strong enough to allow very unusual experiences of touch felt on a cardboard box and experiences of touch produced at a distance, as if by supernatural causation. These findings suggest that one's visual body image is explained away during experience of the illusion and they may be of further importance to understanding the role of experience in delusion formation. The findings of touch on non-hand objects may help reconcile conflicting results in this area of research. In addition, new evidence is provided that relates to the recently discovered psychologically induced temperature changes that occur during the illusion. (shrink)

We show how an epistemology informed by cognitive science promises to shed light on an ancient problem in the philosophy of mathematics: the problem of exactness. The problem of exactness arises because geometrical knowledge is thought to concern perfect geometrical forms, whereas the embodiment of such forms in the natural world may be imperfect. There thus arises an apparent mismatch between mathematical concepts and physical reality. We propose that the problem can be solved by emphasizing the ways in which the (...) brain can transform and organize its perceptual intake. It is not necessary for a geometrical form to be perfectly instantiated in order for perception of such a form to be the basis of a geometrical concept. (shrink)

According to one theory, the brain is a sophisticated hypothesis tester: perception is Bayesian unconscious inference where the brain actively uses predictions to test, and then refine, models about what the causes of its sensory input might be. The brain’s task is simply continually to minimise prediction error. This theory, which is getting increasingly popular, holds great explanatory promise for a number of central areas of research at the intersection of philosophy and cognitive neuroscience. I show how the theory can (...) help us understand striking phenomena at three cognitive levels: vision, sensory integration, and belief. First, I illustrate central aspects of the theory by showing how it provides a nice explanation of why binocular rivalry occurs. Then I suggest how the theory may explain the role of the unified sense of self in rubber hand and full body illusions driven by visuotactile conflict. Finally, I show how it provides an approach to delusion formation that is consistent with one-deficit accounts of monothematic delusions. (shrink)

What grounds my experience of my body as my own? The body that one experiences is always one’s own, but it does not follow that one always experiences it as one’s own. One might even feel that a body part does not belong to oneself despite feeling sensations in it, like in asomatognosia. The article aims at understanding the link between bodily sensations and the sense of ownership by investigating the role played by the body schema.

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)

In the current study we look at whether subjective and proprioceptive aspects of selfrepresentation are separable components subserved by distinct systems of multisensory integration. We used the rubber hand illusion to draw the location of the ‘self’ away from the body, towards extracorporeal space , thereby violating top-down information about the body location. This was compared with the traditional RHI which drew position of the ‘self’ towards the body . We were successfully able to draw proprioceptive position of the limbs (...) in and out from the body suggesting body perception is a purely bottom-up process, resistant to top-down effects. Conversely, we found subjective self-representation was altered by the violation of top-down body information – as the strong association of subjective and proprioceptive factors found in the In Condition became non-significant in the Out Condition. Interestingly, we also found evidence that subjective embodiment can modulate tactile perception. (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)

In this model consciousness is a form of memory. We are essentially “living in the past” as our experience, the qualia, is always of past events. Consciousness represents the storage of past events for use in future situations and it is altered by external experience of the organism. Psychological frameworks of conditioning and learning theory are used to explain this model along with recent neuropsychological research on synaesthesia and phantom limb pain. Consciousness results from the gradual evolutionary development of the (...) human information processing function. Language is hypothesised to have evolved at a pre-conscious stage of human development as a function of the need for ‘within-organism’ data storage. Communication with others may not have been the initial evolutionary advantage conferred by language. The later incidental use of language as a communication tool, which results in the reflecting back of one’s experience through others, is what has triggered a conscious experience. (shrink)

Obsessive-compulsive disorder (OCD) is a deeply enigmatic psychiatric condition associated with immense suffering worldwide. Efficacious therapies for OCD, like exposure and response prevention (ERP) are sometimes poorly tolerated by patients. As many as 25 percent of patients refuse to initiate ERP mainly because they are too anxious to follow exposure procedures. Accordingly, we proposed a simple and tolerable (immersive yet indirect) low-cost technique for treating OCD that we call “multisensory stimulation therapy.” This method involves contaminating a rubber hand during the (...) so-called “rubber hand illusion” (RHI) in which tactile sensations may be perceived as arising from a fake hand. Notably, Jalal and Ramachandran (2015), showed that such fake hand contamination during the RHI provokes powerful disgust reactions in healthy volunteers. In the current study, we explored the therapeutic potential of this novel approach. OCD patients (n = 29) watched as their hidden real hand was being stroked together with a visible fake hand; either synchronously (inducing the RHI) (i.e., the experimental condition; n = 16) or asynchronously (i.e., the control condition; n = 13). After 5 minutes of tactile stimulation, the rubber hand was contaminated with fake feces, simulating conventional exposure therapy. Intriguingly, results suggested sensory assimilation of contamination sensations into the body image via the RHI: patients undergoing synchronous stimulation did not report greater contamination sensations when the fake hand was initially contaminated relative to asynchronous stroking. But contrary to expectations, they did so after the rubber hand had been contaminated for 5 minutes; as assessed via disgust facial expressions (a secondary outcome) and in vivo exposure (upon discontinuing the illusion). Further to our surprise, synchronous and asynchronous stroking induced an equally vivid and fast emerging illusion, which helps explain why both conditions initially (5 minutes after initiating tactile stimulation) provoked contamination reactions of equal magnitude. This study is the first to suggest heightened malleability of body image in OCD. Importantly, it may pave the way for a tolerable technique for the treatment of OCD—highly suitable for poorly resourced and emergency settings, including low-income and developing countries with minimal access to high-tech solutions like virtual reality. (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)

Dijkerman & de Haan (D&dH) propose a somatosensory perceptual pathway that informs a consciously accessible body image, and an action pathway that provides information to a body schema, which is not consciously accessible. We argue that the body schema may become accessible to consciousness in some circumstances, possibly resulting from cross talk, but that this may be detrimental to skilled movement production.

The main suggestions and objections raised by Don Ihde and Charles Lenay to my ‘Technology and the body: the (im)possibilities of re-embodiment’ are summarized and discussed. On the one hand, I agree that we should pay more attention to whole body experience and to further resisting Cartesian assumptions in the field of cognitive neuroscience and philosophy of cognition. On the other hand, I explain that my account in no way presupposes the myth of ‘natural man’ or of a natural, delineated (...) body from before the fall into technology. (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)

This paper investigates the role of a pre-existing body-model that is an enabling constraint for the incorporation of objects into the body. This body-model is also a basis for the distinction between body extensions (e.g., in the case of tool-use) and incorporation (e.g., in the case of successful prosthesis use). It is argued that, in the case of incorporation, changes in the sense of body-ownership involve a reorganization of the body-model, whereas extension of the body with tools does not involve (...) changes in the sense of body-ownership. (shrink)

The parietal cortex is divided into two major functional regions: the anterior parietal cortex that includes primary somatosensory cortex, and the posterior parietal cortex (PPC) that includes the rest of the parietal lobe. The PPC contains multiple representations of space. In Dijkerman & de Haan's (D&dH's) model, higher spatial representations are separate from PPC functions. This model should be developed further so that the functions of the somatosensory system are integrated with specific functions within the PPC and higher spatial representations. (...) Through this further specification of the model, one can make better predictions regarding functional interactions between somatosensory and visual systems. (shrink)

Clinically significant delusion is a symptom of a number of mental illnesses. We rely on what a person says and how she behaves in order to identify if she has this symptom and it is clear from the literature that delusions are heterogeneous and extremely difficult to define. People with active delusions were interviewed to explore what it is like to develop and experience delusion. The transcribed interview data was analysed to identify themes and narrative trajectories that help to explain (...) the phenomenon. Results showed that delusions can sometimes provide pragmatic benefits and that the genesis of some delusions can be characterised in terms of the enactivist notion of affective framing. Affective framing is a term that captures the background emotions that enable know-how in terms of goal directed action and cognition. If a person’s affective frame alters the world is no longer understood and know-how is lost. The way in which a person relates to her environment can be highly anomalous thus requiring her to find an extraordinary explanation. I argue that delusions arise as a result of a breakdown in affective framing and offer a conceptualisation of delusion supported by empirical findings. (shrink)

Recent studies have shown the importance of integrating multisensory information in the body representation for constituting self-consciousness. However, one idea that has received only scant attention is that our body representation is also constituted by knowledge of bodily visual characteristics . Here in two experiments we used a full body crossmodal congruency task in which visual distractors were presented on a photograph of the participant, another person, who was either familiar or unfamiliar, or an object. Results revealed that during the (...) ‘self-condition’ CCEs were enhanced compared to the ‘other condition’. The CCE was similar for unfamiliar and familiar others. CCEs for the object condition were significantly smaller. The results show that presentation of an irrelevant image of a body affects multimodal processing and that the effect is enhanced when that image is of the self. The results hold intriguing implications for body representation in social situations. (shrink)

Modern computer-based applications often require the user to interact with avatars. Depending on the task at hand, spatial dissociation between the orientations of the user and the avatars might arise. As a consequence, the user has to adopt the avatar's perspective and identify herself/himself with the avatar, possibly changing the user's self-representation in the process. The present study aims to identify the conditions that benefit this change of perspective with objective performance measures and subjective self-estimations by integrating the idea of (...) avatar-ownership into the cognitive phenomenon of spatial compatibility. Two different instructions were used to manipulate a user's perceived ownership of an avatar used in otherwise identical situations. Users with the high-ownership instruction reported higher levels of perceived ownership of the avatar and showed larger spatial compatibility effects from the avatar's point of view in comparison to the low ownership instruction. This supports the hypothesis that perceived ownership benefits perspective taking. (shrink)

The body is made up of parts. This basic assumption is central in most neuroscientific studies of bodily sensation, body representation and motor action. Yet, the assumption has rarely been considered explicitly. We may indeed ask how the body is internally segmented and how body parts can be defined. That is, how can we sketch the mereology of the body? Here we distinguish between a somatosensory mereology and a motor mereology.

The functions of the somatosensory system are multiple. We use tactile input to localize and experience the various qualities of touch, and proprioceptive information to determine the position of different parts of the body with respect to each other, which provides fundamental information for action. Further, tactile exploration of the characteristics of external objects can result in conscious perceptual experience and stimulus or object recognition. Neuroanatomical studies suggest parallel processing as well as serial processing within the cerebral somatosensory system that (...) reflect these separate functions, with one processing stream terminating in the posterior parietal cortex (PPC), and the other terminating in the insula. We suggest that, analogously to the organisation of the visual system, somatosensory processing for the guidance of action can be dissociated from the processing that leads to perception and memory. In addition, we find a second division between tactile information processing about external targets in service of object recognition and tactile information processing related to the body itself. We suggest the posterior parietal cortex subserves both perception and action, whereas the insula principally subserves perceptual recognition and learning. (shrink)

I survey some unusual phenomena in which the body seems to be projected into other things. I argue that these phenomena should not be understood as illusions, as erroneous distortions of an objective body, but as indicating that the body is first of all a being absorbed in outside things. The usual questions about perception are thus reversed: the question is not how the outside world is represented in an inside, but how a moving body ecstatically absorbed in things ever (...) breaks out of that absorption. My suggested answer involves movement and has implications for rethinking nature. (shrink)

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)

Here, we assess the usefulness of first-person methods for the study of embodiment during the rubber hand illusion (RHI). Participants observed a rubber hand being stroked synchronously and asynchronously with their concealed hand after which they made proprioceptive judgments about the location of their hand and completed a self-report questionnaire. A randomly selected cohort was further interviewed during the illusion and their transcripts analyzed using interpretative phenomenological analysis (IPA). Results showed that the IPA group experienced a more intense embodied experience (...) during the RHI, measured by proprioceptive distortion and self-report. IPA revealed four main themes of embodied experience: recalibration of the body schema; violation of the body schema; multisensory integration; and illusory experience over time. The report of agency was a significant predictor of proprioceptive distortion. This study shows how first-person methodologies can be empirically rigorous and how the introspective interview provides a rich, detailed account of embodied experience. (shrink)

This article provides a phenomenological analysis of the difference between self-recognition and recognition of another, while referring to some contemporary neuroscientific studies on the rubber hand illusion. It examines the difference between these two forms of recognition on the basis of Husserl’s and Merleau-Ponty’s work. It argues that both phenomenologies, despite their different views on inter-subjectivity, allow for the specificity of recognition of another. In explaining self-recognition, however, Husserl’s account seems less convincing. Research concerning the rubber hand illusion has confirmed (...) that self-recognition involves more than an immediate experience of oneself. Merleau-Ponty’s later work, describing self-recognition as the result of assimilative identification, will be used to explain the possibility of illusion between one’s “hereness” and “thereness”. The possibility of this illusion is inherent to self-recognition, while it is lacking in recognition of another. (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)