What is it like to have a body?

Few questions in psychology are as fundamental or as elusive as the sense of one’s own body. Despite widespread recognition of the link between body and self, psychology has only recently developed methods for the scientific study of bodily awareness. Experimental manipulations of embodiment in healthy volunteers have allowed important advances in knowledge. Synchronous multisensory inputs from different modalities play a fundamental role in producing ‘body ownership’, the feeling that my body is ‘mine’. Indeed, appropriate multisensory stimulation can induce ownership over external objects, virtual avatars, and even other people’s bodies. We argue that bodily experience is not monolithic, but has measurable internal structure and components that can be identified psychometrically and psychophysically, suggesting the apparent phenomenal unity of self-consciousness may be illusory. We further review evidence that the sense of one’s own body is highly plastic, with representations of body structure and size particularly prone to multisensory influences

Deficits in agency in schizophrenia, and additional deficits in body image, body schema, and internal timing, in passivity symptoms

Individuals with schizophrenia, particularly those with passivity symptoms, may not feel in control of their actions, believing them to be controlled by external agents. Cognitive operations that contribute to these symptoms may include abnormal processing in agency as well as body representations that deal with body schema and body image. However, these operations in schizophrenia are not fully understood, and the questions of general versus specific deficits in individuals with different symptom profiles remain unanswered. Using the projected-hand illusion (a digital video version of the rubber-hand illusion) with synchronous and asynchronous stroking (500 ms delay), and a hand laterality judgment task, we assessed sense of agency, body image, and body schema in 53 people with clinically stable schizophrenia (with a current, past, and no history of passivity symptoms) and 48 healthy controls. The results revealed a stable trait in schizophrenia with no difference between clinical subgroups (sense of agency) and some quantitative (specific) differences depending on the passivity symptom profile (body image and body schema). Specifically, a reduced sense of self-agency was a common feature of all clinical subgroups. However, subgroup comparisons showed that individuals with passivity symptoms (both current and past) had significantly greater deficits on tasks assessing body image and body schema, relative to the other groups. In addition, patients with current passivity symptoms failed to demonstrate the normal reduction in body illusion typically seen with a 500 ms delay in visual feedback (asynchronous condition), suggesting internal timing problems. Altogether, the results underscore self-abnormalities in schizophrenia, provide evidence for both trait abnormalities and state changes specific to passivity symptoms, and point to a role for internal timing deficits as a mechanistic explanation for external cues becoming a possible source of self-body input

Demand characteristics confound the rubber hand illusion

Reports of experiences of ownership over a fake hand following simple multisensory stimulation (the ‘rubber hand illusion’) have generated an expansive literature. Because such reports might reflect suggestion effects, demand characteristics are routinely controlled for by contrasting agreement ratings for ‘illusion’ and ‘control’ conditions. However, these methods have never been validated, and recent evidence that response to imaginative suggestion (‘phenomenological control’) predicts illusion report prompts reconsideration of their efficacy. A crucial assumption of the standard approach is that demand characteristics are matched across conditions. Here, a quasi-experiment design was employed to test demand characteristics in rubber hand illusion reports. Participants were provided with information about the rubber hand illusion procedure (text description and video demonstration) and recorded expectancies for standard ‘illusion’ and ‘control’ statements. Expectancies for control and illusion statements in synchronous and asynchronous conditions were found to differ similarly to published illusion reports. Therefore, rubber hand illusion control methods which have been in use for 22 years are not fit for purpose. Because demand characteristics have not been controlled in illusion report in existing studies, the illusion may be, partially or entirely, a suggestion effect. Methods to develop robust controls are proposed. That confounding demand characteristics have been overlooked for decades may be attributable to a lack of awareness that demand characteristics can drive experience in psychological science

A robot hand testbed designed for enhancing embodiment and functional neurorehabilitation of body schema in subjects with upper limb impairment or loss.

Many upper limb amputees experience an incessant, post-amputation "phantom limb pain" and report that their missing limbs feel paralyzed in an uncomfortable posture. One hypothesis is that efferent commands no longer generate expected afferent signals, such as proprioceptive feedback from changes in limb configuration, and that the mismatch of motor commands and visual feedback is interpreted as pain. Non-invasive therapeutic techniques for treating phantom limb pain, such as mirror visual feedback (MVF), rely on visualizations of postural changes. Advances in neural interfaces for artificial sensory feedback now make it possible to combine MVF with a high-tech "rubber hand" illusion, in which subjects develop a sense of embodiment with a fake hand when subjected to congruent visual and somatosensory feedback. We discuss clinical benefits that could arise from the confluence of known concepts such as MVF and the rubber hand illusion, and new technologies such as neural interfaces for sensory feedback and highly sensorized robot hand testbeds, such as the "BairClaw" presented here. Our multi-articulating, anthropomorphic robot testbed can be used to study proprioceptive and tactile sensory stimuli during physical finger-object interactions. Conceived for artificial grasp, manipulation, and haptic exploration, the BairClaw could also be used for future studies on the neurorehabilitation of somatosensory disorders due to upper limb impairment or loss. A remote actuation system enables the modular control of tendon-driven hands. The artificial proprioception system enables direct measurement of joint angles and tendon tensions while temperature, vibration, and skin deformation are provided by a multimodal tactile sensor. The provision of multimodal sensory feedback that is spatiotemporally consistent with commanded actions could lead to benefits such as reduced phantom limb pain, and increased prosthesis use due to improved functionality and reduced cognitive burden

Ghost hand: My hand is not mine

Synchronous visuo-tactile stimulation of the type in the rubber hand illusion (RHI)^1-3^ and in out of body experience (OBE)^4,5^ can induce the brain to incorporate external objects or images into a part or whole of body image. Whether in the context of RHI or OBE, since the participant passively receives visuo-tactile stimulations, body image appears only with the sense of ownership (SoO), not with the sense of agency (the registration that we are the initiators of our actions; SoA)^6,7^. Insofar as self-consciousness as a body image is a unity acting in its environments, body image has to be investigated in the relationship between SoO and SoA^8,9^. It requires an experimental condition in which SoO and SoA can be independently separated in an active condition. However, no experimental condition that is opposite to RHI and OBE in which a subject can feel SoA but not SoO has been proposed to date^10^. Here, we show that a person loses SoO for his own hand that he can freely move by his own will when he sees himself in a lateral view through a head mounted display. It was previously thought that SoO can be represented by synchronous inter-modal stimulations^10^, and that SoO appears to be complemented by SoA11. Our findings show that SoO can be lost under a synchronous visuo-proprioceptive condition while SoA can be maintained. SoO and SoA are two aspects of body representation, and similar dissociations have been proposed in various contexts, such as body image and body schema^12,13^, and 'Acting I' and 'Mine'^14^. Our result suggests that the two-centric-self consisting of SoA and SoO can enhance dynamically robust self-consciousness

Real Virtuality: A Code of Ethical Conduct. Recommendations for Good Scientific Practice and the Consumers of VR-Technology

The goal of this article is to present a first list of ethical concerns that may arise from research and personal use of virtual reality (VR) and related technology, and to offer concrete recommendations for minimizing those risks. Many of the recommendations call for focused research initiatives. In the first part of the article, we discuss the relevant evidence from psychology that motivates our concerns. In Section “Plasticity in the Human Mind,” we cover some of the main results suggesting that one’s environment can influence one’s psychological states, as well as recent work on inducing illusions of embodiment. Then, in Section “Illusions of Embodiment and Their Lasting Effect,” we go on to discuss recent evidence indicating that immersion in VR can have psychological effects that last after leaving the virtual environment. In the second part of the article, we turn to the risks and recommendations. We begin, in Section “The Research Ethics of VR,” with the research ethics of VR, covering six main topics: the limits of experimental environments, informed consent, clinical risks, dual-use, online research, and a general point about the limitations of a code of conduct for research. Then, in Section “Risks for Individuals and Society,” we turn to the risks of VR for the general public, covering four main topics: long-term immersion, neglect of the social and physical environment, risky content, and privacy. We offer concrete recommendations for each of these 10 topics, summarized in Table 1

Malleability of the self: electrophysiological correlates of the enfacement illusion

Self-face representation is fundamentally important for self-identity and self-consciousness. Given its role in preserving identity over time, self-face processing is considered as a robust and stable process. Yet, recent studies indicate that simple psychophysics manipulations may change how we process our own face. Specifically, experiencing tactile facial stimulation while seeing similar synchronous stimuli delivered to the face of another individual seen as in a mirror, induces 'enfacement' illusion, i.e. the subjective experience of ownership of the other’s face and a bias in attributing to the self, facial features of the other person. Here we recorded visual Event-Related Potentials elicited by the presentation of self, other and morphed faces during a self-other discrimination task performed immediately after participants received synchronous and control asynchronous Interpersonal Multisensory Stimulation (IMS). We found that self-face presentation after synchronous as compared to asynchronous stimulation significantly reduced the late positive potential (LPP; 450-750 ms), a reliable electrophysiological marker of self-identification processes. Additionally, enfacement cancelled out the differences in LPP amplitudes produced by self- and other-face during the control condition. These findings represent the first direct neurophysiological evidence that enfacement may affect self-face processing and pave the way to novel paradigms for exploring defective self-representation and self-other interactions

The Evolution of Stop-motion Animation Technique Through 120 Years of Technological Innovations

Stop-motion animation history has been put on paper by several scholars and practitioners who tried to organize 120 years of technological innovations and material experiments dealing with a huge literature. Bruce Holman (1975), Neil Pettigrew (1999), Ken Priebe (2010), Stefano Bessoni (2014), and more recently Adrián Encinas Salamanca (2017), provided the most detailed even tough partial attempts of systematization, and designed historical reconstructions by considering specific periods of time, film lengths or the use of stop-motion as special effect rather than an animation technique. This article provides another partial historical reconstruction of the evolution of stop-motion and outlines the main events that occurred in the development of this technique, following criteria based on the innovations in the technology of materials and manufacturing processes that have influenced the fabrication of puppets until the present day. The systematization follows a chronological order and takes into account events that changed the technique of a puppets’ manufacturing process as a consequence of the use of either new fabrication processes or materials. Starting from the accident that made the French film-pioneer Georges Méliès discover the trick of the replacement technique at the end of the nineteenth century, the reconstruction goes through 120 years of experiments and films. “Build up” puppets fabricated by the Russian puppet animator Ladislaw Starevicz with insect exoskeletons, the use of clay puppets and the innovations introduced by LAIKA entertainment in the last decade such as Stereoscopic photography and the 3D computer printed replacement pieces, and then the increasing influence of digital technologies in the process of puppet fabrication are some of the main considered events. Technology transfers, new materials’ features, innovations in the way of animating puppets, are the main aspects through which this historical analysis approaches the previously mentioned events. This short analysis is supposed to remind and demonstrate that stop-motion animation is an interdisciplinary occasion of both artistic expression and technological experimentation, and that its evolution and aesthetic is related to cultural, geographical and technological issues. Lastly, if the technology of materials and processes is a constantly evolving field, what future can be expected for this cinematographic technique? The article ends with this open question and without providing an answer it implicitly states the role of stop-motion as a driving force for innovations that come from other fields and are incentivized by the needs of this specific sector