While recently binge watching Game of Thrones, I frequently found myself reacting to particularly graphic scenes of violence as though I were about to directly experience those horrors. We have all had moments when we physically feel like we can feel the pain of others. But some experiences can feel like much more – like in a first-person video game or the famous rubber hand illusion. In those cases, it is unclear whether it is empathy at work – via mirror neurons that allow us to anticipate pain – or if it is case of embodiment, where we feel a sense of body ownership or an extension of ourselves. A new study seeks to disentangle the phenomenon, suggesting that perspective could be the key.
To explore the role of body-ownership in how people perceive pain, subjects observed video clips showing either a needle penetrating or a Q-tip touching a hand-model, presented either in first-person or in third-person perspective. The study used a combined non-invasive brain stimulation technique (TMS) with a technique called electromyography, which records electrical activity in muscles, to see the physical response to the observation of pain.
Past studies of this topic have all involved subjects observing pain on others from the first person, thus inviting the question of whether subjects viewed the external hand as part of their own body (embodiment) or whether it was truly the result of anticipating pain and thus the physiological basis for empathy. “In the present study, we aimed at disentangling the empathy and the ownership hypothesis by manipulating the perspective of the observed hand model receiving pain, so that it could be a first-person perspective, the one in which embodiment occurs, or a third-person perspective, the one in which, in everyday life, we perceive the body parts of others,” says Francesca Garbarini of the University of Turin, senior author on the new study in the Journal of Cognitive Neuroscience.
The “empathy hypothesis” predicts a freezing motor response in both the first and third person scenarios. However, the researchers found that subjects experienced a freezing effect only when observing the hand in first person
CNS spoke with Garbarini about the motivation for the study and its implications.
CNS: How did you become personally interested in this research area?
Garbarini: The general idea of the study has been formulated during a review-round of a previous paper of ours, when an anonymous reviewer suggested we consider for our discussion some studies related to the empathy for pain (in particular a series of paper of an Italian colleague, Alessio Avenanti). These papers were strongly influenced by the mirror neurons paradigm that, in the first decade of the 21st century, has greatly influenced cognitive neuroscience. From being first identified in the domain of motor movement, a “mirror-matching” simulation mechanism has been extended to other domains, including emotional experience – whereby the emotional state of an individual activates corresponding representations in another individual observing that state.
In a seminal paper, Avenanti and colleagues demonstrated that motor responses, similar to those present in one’s own pain, occur as a result of pain observation in others. Our reading of the Avenanti’s works, during the above-mentioned paper revision, has been influenced by a very different concept (i.e. the sense of body ownership) on which we focus in our lab in Turin, thus generating the idea of the present study.
CNS: What have we known previously about pain and empathy?
Garbarini: We have previously known from the literature that a close link between actual pain and motor system activity exists. For instance, when a part of our body comes in contact with painful stimuli, we usually withdraw the affected body part from the source of pain. Different avoidance behaviors may be adopted during pain experiences. Together with “fight and flight” behaviors, a “freezing” behavior has been described as a third option in prey animals, feigning death so that the predator stops the attack. In human, a freezing-like effect has been described in several studies demonstrating that actual pain induces an inhibitory modulation on the motor system, by recording, motor responses from the muscles of the body district receiving pain (corticospinal activity).
In this context, it has been shown that the observation of painful stimuli induces corticospinal inhibition in the observer similar to those recorded during the actual pain. According to the above-mentioned Avenanti and colleagues’ works, this suggests that the observation of other people’s pain may reflect the anticipation of pain in oneself and has been interpreted as the physiological basis of empathy, a conclusion that has had a great impact in the field. Interestingly, all previous studies have presented the visual image of the hand receiving pain from a first person point of view, which is problematic because the hand and the pain stimuli could be attributed to self rather than another person. Thus, the “empathy response” might in fact be due to an embodiment phenomenon (i.e. the experience of another person’s body part as belonging to the own body), related to the sense of body ownership.
CNS: What have we known previously about the sense of body ownership?
Garbarini: The sense of body ownership is a crucial component of the self-consciousness and can be defined as the belief that a specific body part belongs to one’s own body. One of the more compelling demonstrations of the mechanisms subserving the sense of body ownership has been obtained in healthy participants by means of an experimental procedure known as the rubber hand illusion. Essentially, watching a rubber hand being stroked while one’s own unseen hand is stroked synchronously can lead to a sense of ownership over the rubber hand (as self-reported at the body-ownership questionnaire) and to a shift in the perceived position of the real hand (as measured by the proprioceptive drift).
In our lab in Turin, we usually investigate this topic from a neuropsychological perspective, thus using pathological conditions, where the sense of body ownership is dramatically impaired, as a model to understand the construction of self-awareness in normal functioning brain. In recent years, increasing interest for the concept of body-ownership has focused on the perspective through which a body-part is observed and the possibility for the subjects to experience it as part of their own body (i.e., embodiment phenomenon). Converging evidence, coming from both rubber hand illusion in healthy subjects and pathological conditions after brain damage, shows that the embodiment occurs only when a specific body part is located in a position coherent with the subjects’ higher-order and pre-existing body representation, whenever it is perceived from a first-person perspective.
CNS: What were you most excited to find? Were any findings surprising?
Garbarini: In the present study, we demonstrated that a freezing-like motor response, comparable to that found when the subjects receive nociceptive (pain arising from the stimulation of nerve cells) stimuli on their own body, also occurs when the nociceptive stimuli were delivered to someone’s else hand, whenever it is perceived in a first-person perspective, automatically leading to a sort of embodiment. On the contrary, no freezing effect was found when stimuli were presented in a third-person perspective. Thus, we were very excited to find this perspective-dependent effect, suggesting that the motor response of the onlooker can be interpreted as connecting to the concept of body ownership.
Furthermore, we were positively surprised for the results of an additional experiment we devised to answer to a critical comment of an anonymous reviewer. During the paper revision process, we called back the participants and tested them by using the above-described rubber hand procedure, in order to investigate correlations between physiological measures and subjective embodiment disposition. We were very excited to find that the corticospinal excitability was directly related both to the subject’s propensity to experience embodiment, as measured by the rubber hand illusion, and to the extent to which the subjects reported, while observing the hand model being penetrated, to feel “as if” the penetrated hand was part of their own body.
CNS: What is the takeaway message you most want people to understand about this work?
Does it change how we should think about empathy?
Garbarini: In the specific context of this experiment, our data suggest that the motor response under discussion is related to an embodiment phenomenon, related to the sense of body ownership. More in general, the present findings make me think about the importance of the theoretical paradigms we have in mind while we designed our study and interpreted our results. Although, as previously described by the mirror-matching simulation theory, the emotional state of an individual activates corresponding representations in another individual observing that state, the present findings underline the importance, in the normal functioning of the human brain, of a specific neural process that binds self-awareness to one’s own body, as opposed to other bodies. In particular, these data are suggestive of an “affective” conception of body-ownership, recently proposed by the French philosopher Frederique de Vignemont, indicating that the body I feel as my own is the body I care more about, the one to which I react when under threat.
-Lisa M.P. Munoz
