Although it is unquestionable that the experience of pain is typically accompanied by body postures/movements, little research has been conducted so far that aimed at classifying or describing body movements accompanying pain using objective assessment tools. Reasons for the lack of research might stem from the complexity and variability of bodily movements and the lack of instruments to objectively assess them. Moreover, given that body movements are believed to have a primary pain management and not a primary communicative function (Prkachin 1986), they do not need to be as distinct or as definable as facial expressions. Given that the origin of pain, the quality of pain, and the body areas/body parts being affected can vary immensely, body movements aiming at reducing or controlling the pain can also be expected to vary immensely. Nevertheless, despite this enormous diversity, there seem to be some body postures/movements that have repeatedly been observed across different types of pain and that might be pain indicative for various types of pain. These body movements are guarding (abnormally slow, stiff, interrupted or rigid movement), bracing (a stiff, static position) and rubbing the painful area (Labus et al. 2003).

So far, even less is known about vocalisation changes occurring during pain. Although it is acknowledged that pain experiences are accompanied by paralinguistic vocalisations – such as crying, shouting, groaning – studies are lacking that have tried to investigate these pain-indicative vocalisations using specialised voice analyses tools. Using voice analyses tools, the following parameters should be assessed in order to better characterise pain-indicative vocalisations: frequency, voice intensity, formants and voice quality as well as temporal characteristics (Scherer et al. 2003). Only when assessing and analysing these parameters we will be able to characterise pain-indicative vocalisations and possibly differentiate them from paralinguistic vocalisations of other types of emotional states.

Observers are able to differentiate behavioural markers of pain (especially facial expressions) from behavioural responses to other types of affective states (e.g. anger, joy, surprise) well above chance level (Simon et al. 2008; Kappesser and Williams 2002), and this ability to differentiate is already developed by the ages of 5–6 years (Deyo et al. 2004). Even though these findings seem promising, there are also several studies demonstrating substantial shortcomings in pain recognition (e.g. mistaking pain for disgust, underestimation of pain; Chambers et al. 1989; Kappesser et al. 2006; Kunz et al. 2013a), and compared to almost all of the six basic emotional states (anger, disgust, fear, happiness, sadness and surprise), the recognition accuracy for facial pain expressions seems to be the lowest (Simon et al. 2008; Kappesser and Williams 2002). The reasons why behavioural/facial markers of pain can be confused with other emotions are that each single marker by itself does not exclusively occur during pain but also during other emotional states. For example, each of the single facial movements displayed in Fig. 8.1 can also be found during other emotional states, such as happiness (contraction of the muscles surrounding the eyes), during disgust (nose wrinkle) and anger (furrowed brow). Thus, none of the single facial movements by itself can differentiate between pain and other emotional states, but the combinations of facial movements, their temporal patterns and context information, as well as the combination of facial expressions, body posture and paralinguistic vocalisations help us to correctly interpret these behavioural/facial markers of pain.

Interestingly, experience with pain diagnostic and/or pain management by itself does not improve the ability to correctly infer pain from facial expressions (e.g. Lautenbacher et al. 2013); however, a training procedure specifically targeting the facial expressions of pain has been shown to be successful. Solomon et al. (1997) developed such a training procedure to improve recognition accuracy for pain. Based on the finding that pain is accompanied by a specific set of facial movements (Prkachin 1992; Prkachin and Solomon 2008), observers were trained to recognise these facial movements (see Fig. 8.1 where these facial movements are displayed). And indeed, those observers who received this training showed better decoding accuracy compared to a control group (Solomon et al. 1997). Given the clinical importance of correctly interpreting behavioural/facial markers of pain, such a training seems to be a promising approach.

Based on empirical findings, it is acknowledged that behavioural/facial markers of pain are a mixture of biological dispositions as well as of social learning (Hadjistavropoulos et al. 2011). As for their biological dispositions, it has been shown that infants (including neonates) (Craig et al. 2011) and congenitally blind individuals (Kunz et al. 2012a) display the same patterns or the same types of facial movements in response to pain as sighted adults do (see also Fig. 8.1 for a list of the most frequent pain-indicative facial movements). These findings clearly suggest that facial expressions of pain are “hard-wired”. As regards body movements and vocalisations, empirical findings are lacking so far. Despite facial expressions of pain having been shown to be “hard-wired”, it is also acknowledged that facial responses become modifiable across early and late childhood through social learning experiences and cognitive capacities (Hadjistavropoulos et al. 2011). One very important modification relates to the degree/intensity to which we express pain via our face. Whereas young children tend to show vigorous facial expressions of pain, older children and adults seem to have learned to effectively downregulate their facial expressions of pain (Larochette et al. 2006). In line with this finding, a recent neuroimaging study demonstrated that a low degree of facial expressiveness to pain was associated with higher activation in fronto-striatal structures (Kunz et al. 2011a). Given that these fronto-striatal structures are known to be involved in motor inhibition, this finding suggests that low expressive individuals actively suppress their facial display of pain (Kunz et al. 2011a). When trying to interpret these findings, it has been argued that individuals learn to intentionally suppress the facial display of negative affect (including pain) following culturally/socially learned “display rules”. These display rules represent social norms about when, where and how one should express affective states (Ekman et al. 1969) and are learned already at a young age. Based on this theory, facially responding to pain would be the “default” that individuals learn to suppress due to social/cultural demands (e.g. “big boys don’t cry”, “one mustn’t be oversensitive to pain”). In accordance with this theory, it has been demonstrated in previous studies that social learning and social context indeed influence the degree of facial expressiveness to pain. The presence of others can reduce (e.g. when being together with a stranger) as well as increase (when being together with a loved one) the amount of pain-indicative facial responses depending on the nature of the relationship between observer and sufferer (Karmann et al. 2014; Vervoort et al. 2008). Furthermore, it has been shown that the degree of facial expressiveness to pain can be effectively modulated by different types of learning, with operant conditioning techniques leading to an increase (positive reinforcement of facial expressions of pain) or decrease (positive reinforcement of a neutral expression) in facial expressiveness to noxious stimulation, respectively (Kunz et al. 2011 b). This learned ability to mostly downregulate facial expressions of pain seems to depend on the cognitive status of the individual.