The Faces from China’s Uyghur Detention Camps – John Sudworth

Each person we encounter in the world is a unique perspective that is not the body, but the “self”, which is lodged in the face.

“Thousands of photographs from the heart of China’s highly secretive system of mass incarceration in Xinjiang, as well as a shoot-to-kill policy for those who try to escape, are among a huge cache of data hacked from police computer servers in the region.

The Xinjiang Police Files, as they’re being called, were passed to the BBC earlier this year. After a months-long effort to investigate and authenticate them, they can be shown to offer significant new insights into the internment of the region’s Uyghurs and other Turkic minorities.”

Read the article here.

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Meanings of Pain, Volume 3: Vulnerable or Special Groups of People (2022, Springer)

• First book to describe what pain means in vulnerable or special groups of people
• Clinical applications described in each chapter
• Provides insight into the nature of pain experience across the lifespan

This book, the third and final volume in the Meaning of Pain series, describes what pain means to people with pain in “vulnerable” groups, and how meaning changes pain – and them – over time.

Immediate pain warns of harm or injury to the person with pain. If pain persists over time, more complex meanings can become interwoven with this primitive meaning of threat. These cognitive meanings include thoughts and anxiety about the adverse consequences of pain. Such meanings can nourish existential sufferings, which are more about the person than the pain, such as loss, loneliness, or despair.

Although chronic pain can affect anyone, there are some groups of people for whom particular clinical support and understanding is urgently needed. This applies to “vulnerable” or “special” groups of people, and to the question of what pain means to them. These groups include children, women, older adults, veterans, addicts, people with mental health problems, homeless people, or people in rural or indigenous communities. Several chapters in the book focus on the lived experience of pain in vulnerable adults, including black older adults in the US, rural Nigerians, US veterans, and adults with acquired brain injury. The question of what pain experience could mean in the defenceless fetus, neonate, pre-term baby, and child, is examined in depth across three contributions.

This book series aspires to create a vocabulary on the “meanings of pain” and a clinical framework with which to use it. It is hoped that the series stimulates self-reflection about the role of meaning in optimal pain management.

Meanings of Pain is intended for people with pain, family members or caregivers of people with pain, clinicians, researchers, advocates, and policy makers. Volume I was published in 2016; Volume II in 2019.

Request a sample by emailing me: simon.vanrysewyk@utas.edu.au, or vanrysewyk@hotmail.com

Buy the complete book on Springer’s website, here.

FACE Summit 2022

FACE Summit 2022 will take place on May 21, 2022, online and live (School of Face ZOOM Platform), with lectures in English, Spanish and Portuguese. Keynote speakers are exclusive guests of the organizing committee.

The FACE Summit is a registered event from the original idea by Dr. Freitas-Magalhães, PhD, and organized by F-MGI and FEELab/UFP. The FACE Summit motto is “the face is our emotion”. More info: face@facesummit.pt #facesummit2022

I am presenting a keynote presentation, “The Face of Pain: Action, Meaning, and Control”.

Wittgenstein: using our world-view to criticise others?

Ludwig Wittgenstein by Fabrizio Cassetta (2017)

Imagine two communities. One community predicts the seasonal weather following the science of meteorology. Another community predicts the same through consulting the trusted indigenous oracle. The two communities could be members of the same society, but this is not relevant to the story.

Suppose it turns out that meteorology is far more accurate at forecasting the seasonal weather than the oracle. The community that uses meteorology to predict the weather cultivates a disdain for the oracle community, and criticises it as foolish and irrational.

Should the oracle community therefore abandon its customary oracle practice?

Even if we grant that the oracle community is irrational in adhering to its oracle practice, this does not mean that the community must discontinue the practice, since its adherence could be based on particular needs, priorities, or others factors.

For example, the oracle practice could be influenced by the previous generations’ observations and experimentation, which are highly valued. The oracle forecasts are derived from local experiences and communicated in local languages by the indigenous oracle, who is well-known and trusted in the community. The practice is simple, recognisable, and coherent to the community, compared with the complex and probabilistic nature of scientific forecasts.

In the Last Writings on the Philosophy of Psychology (Volume I), philosopher Ludwig Wittgenstein invites the reader to imagine a tribe unfamiliar with the concept of simulated pain. They

… pity anyone who indicates that he is feeling pain. They are unfamiliar with the suspicious attitude toward expressions of pain. A traveller coming from our culture to theirs frequently thinks that a complaint is exaggerated, indeed, that its only purpose is to generate pity; the natives don’t seem to think that way.

A missionary teaches the people our language; in the process he also educates them and under his tutelage they learn to distinguish between a genuine and a pretended expression of pain … They learn our expression: “to feel pain”, and also “to simulate pain”, and the question is: were they taught a new concept of pain?

Had those people overlooked something, and did the teacher bring something to their attention?

And how could they remain unaware of the difference if sometimes they would complain when they were in pain, and sometimes when they were not? Am I to say that they always thought it was the same thing? – Certainly not. Or am I to say that they didn’t notice the difference? – But why not say: the difference wasn’t important to them? (Last Writings on the Philosophy of Psychology, Volume I, 203-205)

In On Certainty (286), Wittgenstein discusses the possibility that a community could incorporate a different world view into its own practices. Thus, it is possible that the oracle community could use both oracle and meteorological information for weather forecasting. If we assume that agriculture in the community is rainfed and vulnerable to climate extremes and change, meteorological information could help farmers and pastoralists in the community cope with climate variability or adapt to climate change. Still, the community could regard the oracle as superior in relation to specific, important indicators, such as onset of rainfall, or amount of rainfall.

Further, if the oracle community is geographically remote, meteorological weather forecasts may not be downscaled or location-specific, thus less effective in addressing the local needs of community farmers and pastoralists. The forecasts could lack reliability, or capacity in the community to interpret them is limited. Here, the oracle practice would continue to have an essential, or predominant, role in the community.

The meaning of coping with chronic pain – video presentation recording

Presented at the International Network for Research into Psychosocial Adjustment to Long-term Conditions (INRePALC)

1st International Online Networking Event
13th–17th September, 2021

Session Description: Let’s discuss what it means to cope with chronic pain – this is not a data presentation. Instead, I attempt to create a sense of enquiry and self-reflection on how to take the meaning of coping with chronic pain and apply it in the clinic. Thinking about what we do, and what the doing represents in the clinic, can be rewarding.

What the face reveals: the experience of pain

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Presented at: De/Constructing the Body: Ancient and Modern Dynamics, Workshop 3:Trans-Formation, April 9, 2021.

Abstract here.

Slide transcript

Slide 2
Human beings are describable in two distinct, but complementary ways: in terms of the way the world is, through scientific descriptions of the causal mechanisms and laws that explain physical things, or, in terms of the way the world seems, through descriptions of personal experiences and meanings.

As a person, I can recognise within myself a perspective or point of view on the world and identify it as belonging to me. Every person has such a unique perspective; this is partly what it means to be a person rather than a physical thing. In contrast, a scientific description of the world does not presuppose any personal point of view. Physical or biological science does not use words like “I”, “here”, or “now”.

Slide 3
The features of personal experience—thought, feeling, speech and action—are amenable to standard scientific explanation as specific changes in the body.

A philosophical assumption held by some neurophysiologists is that a person is identical with his or her body. Person and body are one and the same thing. This assumption is behind the slogan in pain science, “pain is in the brain”.

In terms of personal experience, however, the identity between person and body escapes understanding. For example, when I feel a pain, there is no information or evidence, or nothing that I could discover about my body subsequent to the experience of pain, that could demonstrate it to be false. When I feel a pain, I simply I am in pain.

Slide 4
In person-to-person interactions, we commonly respond to each other as though we are not identical with the human body, but in a compelling sense operating “through” the body, which seems to be a vehicle of thought, emotion, pain or suffering.

We feel that each person we encounter in the world is a unique perspective that is not the body, but the “self”, which is lodged in the face.

Slide 5
Pain is not an action, but a personal experience. Yet, pain reveals itself in those gestures, or expressions, which cannot fail to reveal the person in pain.

People in pain communicate their experience through a range of actions, ranging from self-report, to nonverbal actions, which include paralinguistic vocalisations, bodily activity and facial expressions.

Verbal self-report is mostly voluntary, and relies on reflection and deliberation, whereas nonverbal expression is involuntary and reflexive.

Slide 6
But the involuntary transformations revealed in the face are more meaningful than in other body-parts. This is because body-parts do not have the individuating meaning of the face: the meaning of revealing me, here, now. When I observe another’s pain facial expression, I am not perceiving a physical part of him, as I am when I notice his injured arm or leg. I am meeting him, a real person, who reveals himself in the face.

A person may be perceived by his arm, but not in his arm.

Involuntary facial changes show the person with pain “as he really is”, because he does not fully control them.

We express preference for non-verbal behaviour over verbal behaviour when judging or interpreting the credibility of pain displays.

Slide 7
Pain expressed through the face acquires, for us, an individuality, a personality, that readies us for the human encounter.

Not understanding a face means not seeing where it fits into our gallery of portraits, and therefore not knowing how to properly relate to the person whom it prefigures. One study showed that physicians tended to attribute lower levels of pain to physically attractive patients than physically unattractive patients. Another study found that physically attractive and male patients were perceived as experiencing less pain and disability than physically unattractive and female patients. Finally, in another study, observers judging patient facial pain expressions on video perceived older and less physically attractive patients to be of lower overall functioning.

I can decide to enter into another’s pain expression; or I can decide to remain outside it, as it were, and to see it as a thing apart; perhaps more darkly, as something foreign, or subordinate to my will. How we judge a face may affect the outcomes the patient can achieve.

Slide 8
Pain imposes a significant vulnerability on persons: the vulnerability of a free person who is overwhelmed in his or her body by the presence of pain. This can make the person with pain feel answerable for what he or she experiences. Men who adopt a stoical attitude to their pain are less likely to express pain in the presence of others.

The expression on a face is an offering in the world of mutual responsibilities: it projects into our interpersonal relations a particular person’s “being there”. As soon as I notice pain in another person’s face, my responsibilities are engaged. Facial expressions of pain call on you to respond to me.

The face has this meaning for us because it is the boundary at which the other appears, offering “this person” as one in need of help.

Slide 9
However, expressing pain does not always lead to compassionate reactions, and people are careful about when and with whom they express pain.

Voluntary control of pain through facial actions is normally judged to be an insincere expression of pain, and open to doubt. The controlled pain face is perceived as a mask, which conceals the person lying “behind” it. The expressions on the human face are not always transparent effects of the personal experiences that elicit them, as perhaps they are in non-human mammals. Human beings can deceive through their faces, and children and adults can use the face to fake, and amplify, or suppress, pain.

The capacity to modulate pain expressed through the face has led to difficulty in interpreting the meaning of facially expressed pain. The fidelity with which facial signs mean “pain” is limited to a narrow range of involuntary facial expressions of pain. It is often uncertain whether the presence or absence of information means “pain” or, if they are exaggerated or suppressed consistent with perceived situational demands.

Slide 10
If there is a configuration of facial actions that signals pain, then assessing its presence is amenable to pattern recognition technologies. Substantial progress has been made toward the development of IT-based analysis of pain facial expression.

These systems raise ethical questions about control of patient information.
As these IT systems are used in health care settings, informed consent will need to be obtained for collecting and storing patients’ images, but also for the specific purposes for which those images might be analyzed by these systems.

IT systems can store data as a complete facial image or as a facial template. Facial templates are considered biometric data and thus personally identifiable information. The notion that a photo can reveal private health information is relatively new, and privacy regulations and practices are still catching up. Clinicians should advise patients that there may be limited protections for storing and sharing data when using an facial recognition tool.

What the face reveals: the experience of pain

Abstract submitted to Workshop 3, De/Constructing the Body: Ancient and Modern Dynamics

Pain is not an action; yet it reveals itself in those gestures which cannot fail to disclose and to compromise the person with pain. 

During pain, body-parts are subject to massive involuntary transformations. But the involuntary transformations revealed in the face are more meaningful than in other body-parts. This is because body-parts do not have the individuating meaning of the face: the meaning of revealing me, here, now. When I observe another’s pain facial expression, I am not perceiving a physical part of him, as I am when I notice his injured arm or leg. I am meeting him, a real person, who reveals himself in the face. A person may be perceived by his arm, but not in his arm. The most meaningful features in displays of pain are the eyes, followed by brows, eyelids, mouth, head, forehead, and then other body-parts. Intentional control of pain through facial movements is normally judged by observers to be an insincere expression of pain, and open to doubt. Thus, involuntary facial changes show the person with pain “as he really is” because he does not fully control them, and observers are more obliged to offer help when movements are most involuntary. 

Collage by Alexey Kondakov

The loss of voluntary control over my body during pain, and its dominion over me, create the compelling sense, for me and for others, of an “incarnate” person. Pain imposes a significant vulnerability on persons: the vulnerability of a free person who is overwhelmed in his or her body by the presence of pain. This can make the person with pain feel answerable for what he or she experiences. The expression on a face is an offering in the world of mutual responsibilities: it projects into our inter-personal relations a particular person’s “being there”. As soon as I notice pain in another person’s face, my responsibilities are engaged. Facial expressions of pain call on you to respond to me. The face has this meaning for us because it is the boundary at which the other appears, offering “this person” as one in need of help. This feature is perhaps at the heart of what it means to treat and monitor pain.

Keywords: face; facial expression; pain; meaning; body; involuntary.

“Me seeing you seeing my pain”

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Sculpture by Fabio Viale

Meanings of Pain (Springer International Publishing, 2016) was created to advance understanding of pain experience as a bearer of meaning. Progress in modern biomedicine is necessary to explain pain and to aid in its treatment; yet, preference for biomedical explanation of pain in the field has meant that research and clinical attention to the experience of pain and to common factors of pain, such as meaning, as both a clinical topic and a research method, mostly remains a blind spot in knowledge.

Meaningful changes that we notice in others are often subtle and small changes in facial expression, and are similar to features of clinicians that patients find meaningful, such as aspects of clinician demeanour (enthusiasm, positive personality, attentiveness), which are often embodied in subtle facial expressions, gestures, or particular tones of voice (e.g., Gracely et al. 1985). Pain is a personal experience, not an action; yet it displays itself in those actions in which a human person in pain is revealed to observation (Craig et al. 2010). Body-parts are subject to involuntary changes during pain, such as reflexive withdrawal, but in the social transaction of pain, the involuntary changes revealed in the face are more meaningful than in other body-parts (Prkachin et al. 1983; Craig, 2009). This is because body-parts do not have the individuating meaning of the face: the meaning of revealing me, here, now. The expression on a human person’s face is largely determined by involuntary facial actions; yet, it is the living picture of the person that “peers” from it, and hence a concentrated symbol of the “self”. In facial expressions of pain, the face is not a mere bodily part, but the whole person: the self is spread across its surface, and there displayed.

Intentional control of pain through facial actions is normally judged by observers to be an insincere expression of pain, and open to doubt (Hill & Craig, 2002). The controlled pain face is perceived as a mask, which conceals the person lying “behind” it. The expressions on the human face are not always transparent effects of the personal experiences that elicit them, as perhaps they are in nonhuman mammals. Human beings can deceive through their faces, and children and adults can use the face to fake, as well as exaggerate, or suppress, pain (Williams, 2002). It is possible that deception is possible because we do not distinguish a human person from his or her face. Protective acts such as withdrawal reflexes, guarded postures, and disabled behaviour, can communicate pain to sensitive observers (Sullivan, 2008). But when I observe another’s pain face, I am not meeting a physical part of him, as I am when I notice his injured arm or leg. I am meeting him, a real person, who reveals himself in the face as one like me. There are deceiving faces, but not deceiving arms or legs.

Facial expressions of pain call on you to respond to me. As soon as I notice pain in another person, my responsibilities are engaged. I am held to account for it. The face has this meaning for us because it is the boundary at which the other in pain appears, offering “this person” as one in need of help. This feature is perhaps at the heart of what it means to treat pain. Care of persons in pain would be impossible without the assumption that we can commit ourselves through promises, take responsibility now for some event in the future or the past, and enter into obligations that we hold as not transferable to other persons—all of which are perceived in the face.

We may separate pain from its social meaning, and assign to it an impersonal, “bodily” meaning. However, an observation of pain which, whether or not intentionally, focuses exclusively upon the body-parts of another, but which neglects the preliminary changes in the face, as well as in the voice, hands and posture, perhaps is unethical. The failure to recognise the personal existence of the other in pain is therefore an affront, both to him and to oneself. In separating pain from its social meaning, we remove it from the interpersonal world of social relations, which compels us to recognise human beings as persons and sometimes to compromise or risk ourselves for them.

The most meaningful feature in displays of pain is the eyes, followed by brows, eyelids, mouth, head, forehead, and then other body-parts (Prkachin et al. 1983). Although glances are normally voluntary, they participate in the pattern of involuntary social communication where one person in painful distress is “revealed” in his body to the one who observes him. To turn my eyes to you is a voluntary act; but what I receive from you is not anything I voluntarily do. The eye enables the human person in pain to be displayed to another in his body, and in the act of display to call on the observer to intervene on their behalf. The complex transaction of pain involves the voluntary and the involuntary to co-mingle on the surface of the human body. The joining of minds that begins when an expression of pain is answered with a reciprocated response is partly fulfilled in “me seeing you seeing my pain”, which is not the reciprocity of normal cooperation, but of meaning. I believe many patients with pain desire to experience first-hand this more concentrated form of social recognition.

References

Craig KD. A social communications model of pain. Canadian Psychology/Psychologie Canadienne 2009; 50:22-32.

Craig KD et al. Perceiving pain in others: automatic and controlled mechanisms. J Pain 2010; 11(2):101-8.

Gracely RH et al. Clinicians’ Expectations Influence Placebo Analgesia. Lancet 1985; 1(8419):43.

Hill ML, Craig KD. Detecting deception in pain expressions: The structure of genuine and deceptive facial displays. Pain 2002; 98:135-144.

Prkachin KM et al. Judging nonverbal expressions of pain. Canadian Journal of Behavioural Science/Revue canadienne des sciences du comportement. 1983; 15(4):409.

Sullivan MJL. Toward a biopsychomotor conceptualization of pain. Clin J Pain 2008; 24:281-290.

van Rysewyk S (ed). Meanings of Pain. Springer International Publishing: Switzerland, 2016.

Williams AC. Facial expression of pain: An evolutionary account. Behav Brain Scien 2002; 25:439-488.

A neurobehavioral-polyvagal theory of pain facial expression

The personal experience of pain produces a reliable effect on facial behavior in humans and in nonhuman mammals. Why should pain have a face? What is it for? I will attempt to head towards answering this question by invoking a theoretical framework: polyvagal theory (Porges, 2001, 2006).

1 Polyvagal Theory

According to polyvagal theory (Porges, 2001, 2006), evolution of neural control within the autonomic nervous system (ANS) has tracked three stages, each revealing a specific behavior, and a specific function:

In the first stage, the ancient unmyelinated visceral vagus nerve that enables digestion could respond to danger and pain only by reducing metabolic output and producing immobilization behaviors.

In the second stage, the sympathetic nervous system (SNS) made it possible to increase metabolic activity and inhibit the visceral vagus nerve, thus allowing fight/flight behaviors following perceived threat or pain.

The third stage, which is uniquely mammalian, involves a myelinated vagus that can rapidly control cardiac and bronchi output to enable spontaneous interaction (i.e., engagement or disengagement) with the environment. The interaction of the autonomic nervous system (ANS) with the hypothalamo-pituitary-adrenal (HPA) axis, nervous and immune systems change to maximize response to stressors such as nociception. During nociception, the ANS operates together with nervous, endocrine and immune systems to produce stress (Chapman et al. 2008; Porges, 2001, 2006). In terms of polyvagal theory, pain facial expression is a dynamic autonomic response caused by noxious signaling. In terms of polyvagal-type identity mechanistic theory pain facial expression is a type of behavior that is identical to a type of neurophysiological mechanism; namely, the phylogenetically recent brain-heart-face mechanism.

The expansion of cortex in the third stage increased innervation and neural control of the mammalian face: upper face innervation is bilateral and arises from the supplementary motor area (M2) and the rostral cingulate motor area (M3). Lower face innervation is contralateral and arises from primary motor cortex (M1), ventral lateral premotor cortex, and the caudal cingulate motor cortex (M4) (Morecraft et al. 2004). Human pain facial movements of the eyebrows and upper lip are type identical with negative emotional aspects of pain and activation of M1, M2, M3, whereas facial movements around the eyes are type identical with somatosensory aspects of pain, and activation of M2 and M3 (Kunz et al. 2011). Thus, evolution of cranial anatomy enabled a highly integrated facial representation of the multidimensional experience of pain.

2 Why Pain Should Have a Face

In clinical and experimental settings, the pain face is observed to rapidly appear following noxious stimulation, and diminish concurrent with cessation of the noxious stimulus, or when analgesics are administered (e.g., Craig & Patrick, 1985). The brain-heart-face mechanism is an integrated system with both a somatomotor part controlling the striated facial muscles and a visceromotor part controlling the heart through a myelinated vagus nerve (Porges, 2001, 2006). When the vagal tone to the cardiac pacemaker is high, the myelinated vagus acts as a brake or restraint limiting heart rate. Rapid inhibition and disinhibition of vagal tone to the heart supports the rapid mobilization of facial muscles and formation of the pain face concurrent with pain onset. In humans and nonhuman mammals, the main vagal inhibitory pathways in the myelinated vagus originate in the nucleus ambiguus.

The vagal brake supports the low-metabolic requirements involved in the rapidly appearing and disappearing pain face. Withdrawal of the vagal brake is strongly correlated with the rapid appearance of the pain face; reinstatement of the vagal brake is strongly correlated with the rapid diminishing of the pain face. These correlations are not unique to pain facial expression; similar relationships hold with regard to the vagal brake and the timing and duration of aversive, but non-noxious emotional facial expressions (e.g., Pu et al. 2010), and positive emotional facial expressions (e.g., Kok & Fredrickson, 2010).

In terms of the function of rapid pain face onset and offset, the vagal brake makes it possible for the individual in pain to quickly disengage from source of wounding and pain, concurrent with the rapid appearance or diminishing of pain facial expression, which may offer temporary access to additional metabolic resources to aid healing, recovery and self-soothing behaviors, with likely involvement from care givers.

Concerning aid from others, the vagal brake reliably maps onto specific interaction types observed in mammalian pain events. In pain events comprising the individual in pain and care givers, mammalian behavior is typed according to interpersonal communication through facial expressions, vocalizations, head and hand gestures (Hadjistavropoulos et al. 2011; Porges, 2001, 2006; Williams, 2002). A relevant feature is the rapid ‘switching’ of temporary engagement to temporary disengagement behaviors between the individual in pain and care givers. This interaction type may involve care givers speaking to the one in pain, and then quickly switching to listening; for the one in pain, looking into the face of the care giver, and then quickly switching to vocalizing (Craig et al. 2011; Hadjistavropoulos et al. 2011; Porges, 2001, 2006; Williams, 2002). The brain-heart-face mechanism thus allows the one in pain and the care giver to get the timing right. Some philosophers and neuroscientists claim that evolutionary neurobehavioral solutions to timing problems such as these are implicated in the origin of empathy and ultimately consciousness itself (Churchland, 2002; Cole, 1998; Engen & Singer, 2012; van Rysewyk, 2011).

However, if pain is severe or chronic and the vagal brake is withdrawn (or dysfunctional), the concurrency of increased pain facial expression, cardiac output, and other mobilization behaviors (i.e., increased SNS and HPA output), means that, if care giving is to succeed in promoting healing and recovery, the care giver’s vagal brake must be dynamically reinstated. By applying their own vagal brake, care givers may regulate their own visceral distress and thereby succeed in allocating valuable metabolic resources to communicate safety to the one in pain (and themselves) through calming facial and head behaviors, eye gaze, and prosodic vocalizations (i.e., increasing the vagal brake decreases SNS and HPA output). Since the vagal brake of the person in pain has been provisionally withdrawn, the care giver is effectively an integrated external brain-heart-face mechanism (cf. Tantam, 2009, the ‘interbrain’).

Thus, the pain facial muscles function as neural timekeepers detecting and expressing features of safety and danger that cue the one in pain to quickly disengage from the source of wounding and pain, simultaneous with the rapid appearance or attenuation of pain facial activity, and also cue others who can help.

References

Chapman, C. R., Tuckett, R. P., & Song, C. W. (2008). Pain and stress in a systems perspective: reciprocal neural, endocrine, and immune interactions. Journal of Pain, 9(2), 122-145.

Churchland, P. S. (1989). Neurophilosophy: Toward a Unified Science of the Mind-Brain. Cambridge, Mass.: MIT Press.

Cole, J. (1998) About face. Cambridge, Mass.: The MIT Press.

Craig, K. D., & Patrick, C. J. (1985). Facial expression during induced pain. Journal of Personality and Social Psychology, 48(4), 1080-1091.

Craig, K. D., Prkachin, K. M., & Grunau, R. E. (2011). .The facial expression of pain. In D. C. Turk, & R. Melzack, Handbook of Pain Assessment, 2^nd Edition (pp. 117-133). New York: The Guilford Press.

Engen, H. G., & Singer, T. (2012). Empathy circuits. Current Opinion in Neurobiology, 23, 1-8.

Hadjistavropoulos, T., Craig, K. D., Duck, S., Cano, A., Goubert, L., Jackson, P. L., Mogil, J. S., Rainville, P., Sullivan, M. J. L., de C. Williams, Amanda C., Vervoort, T., & Fitzgerald, T. D. (2011). A biopsychosocial formulation of pain communication. Psychological Bulletin, 137(6), 910-939.

Kok, B. E., & Fredrickson, B. L. (2010). Upward spirals of the heart: Autonomic flexibility, as indexed by vagal tone, reciprocally and prospectively predicts positive emotions and social connectedness. Biological Psychology, 85(3), 432-436.

Kunz, M., Lautenbacher, S., LeBlanc, N., & Rainville, P. (2011). Are both the sensory and the affective dimensions of pain encoded in the face? Pain, 153(2), 350-358.

Morecraft, R. J., Stilwell-Morecraft, K. S., & Rossing, W. R. (2004). The Motor Cortex and Facial Expression: New Insights From Neuroscience. The Neurologist, 10(5), 235-249.

Porges, S. W. (2001). The polyvagal theory: phylogenetic substrates of a social nervous system. International Journal of Psychophysiology, 42(2), 123-146.

Porges, S. W. (2006). Emotion: An Evolutionary By‐Product of the Neural Regulation of the Autonomic Nervous System. Annals of the New York Academy of Sciences, 807(1), 62-77.

Pu, J., Schmeichel, B. J., & Demaree, H. A. (2010). Cardiac vagal control predicts spontaneous regulation of negative emotional expression and subsequent cognitive performance. Biological Psychology, 84(3), 531-540.

van Rysewyk, S. (2011). Beyond faces: The relevance of Moebius Syndrome to emotion recognition and empathy. In: A. Freitas-Magalhães (Ed.), ‘Emotional Expression: The Brain and the Face’ (V. III, Second Series), University of Fernando Pessoa Press, Oporto: pp. 75-97.

Williams, A. C. D. C. (2002). Facial expression of pain: an evolutionary account. Behavioral and Brain Sciences, 25(4), 439-455.