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 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)

There is an increasing amount of empirical work investigating the sense of agency, i.e. the registration that we are the initiators of our own actions. Many studies try to relate the sense of agency to an internal feed-forward mechanism, called the ‘‘comparator model’’. In this paper, we draw a sharp distinction between a non-conceptual level of feeling of agency and a conceptual level of judgement of agency. By analyzing recent empirical studies, we show that the comparator model is not able (...) to explain either. Rather, we argue for a two-step account: a multifactorial weighting process of different agency indicators accounts for the feeling of agency, which is, in a second step, further processed by conceptual modules to form an attribution judgement. This new framework is then applied to disruptions of agency in schizophrenia, for which the comparator model also fails. Two further extensions are discussed: We show that the comparator model can neither be extended to account for the sense of ownership (which also has to be differentiated into a feeling and a judgement of ownership) nor for the sense of agency for thoughts. Our framework, however, is able to provide a unified account for the sense of agency for both actions and thoughts. (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.

Although philosophical approaches to the self are diverse, several of them are relevant to cognitive science. First, the notion of a 'minimal self', a self devoid of temporal extension, is clarified by distinguishing between a sense of agency and a sense of ownership for action. To the extent that these senses are subject to failure in pathologies like schizophrenia, a neuropsychological model of schizophrenia may help to clarify the nature of the minimal self and its neurological underpinnings. Second, there is (...) good evidence to suggest that although certain aspects of the minimal self are primitive and embodied, other aspects may be accessed only in reflective consciousness. Employing a modified concept of the minimal self, it may be possible to construct a robotic form of non-conscious self-reference that depends on an interaction between the robotic body and its environment. In contrast to the minimal self, the narrative self involves continuity over time and is directly relevant to discussions of memory and personal identity. There is growing consensus among philosophers and cognitive scientists about the importance of narrative and its relation to episodic memory and left-hemisphere functions. There are, however, at least two different views of how the narrative self is structured. On one model it is nothing more than an abstract point. On a more extended view, proposed here, the self is a rich amalgam of narratives that allows for the equivocations, contradictions, and self-deceptions of personal life. Even in this case, however, neurocognitive models contribute to our understanding of how narrative identity is structured. (shrink)

The rubber hand illusion is a perceptual illusion in which a model hand is experienced as part of one’s own body. In the present study we directly compared the classical illusion, based on visuotactile stimulation, with a rubber hand illusion based on active and passive movements. We examined the question of which combinations of sensory and motor cues are the most potent in inducing the illusion by subjective ratings and an objective measure . In particular, we were interested in whether (...) the combination of afferent and efferent signals in active movements results in the same illusion as in the purely passive modes. Our results show that the illusion is equally strong in all three cases. This demonstrates that different combinations of sensory input can lead to a very similar phenomenological experience and indicates that the illusion can be induced by any combination of multisensory information. (shrink)