Sex differences in the decoding of pain-related body postures

Experimental Pain Picture System (EPPS): Development and Validation

Pain-related pictures are useful for studying how individuals respond to pain-related stimulation. Such pictures can occasionally be found in databases for affective pictures. However, a validated database specifically for pain-related pictures is not available yet. In 2 experiments (N = 185 and 103, respectively), we developed and validated the Experimental Pain Pictures System (EPPS). In both experiments, negative valence, arousal, and painfulness ratings were compared between neutral-, sad-, and pain-related pictures. The pain-related pictures represented both deep and superficial somatic pain. Across the 2 experiments, pain-related pictures were judged as more negative, arousing, and painful than neutral pictures and more painful than sad pictures. The final EPPS contains 50 pictures of different painful events considered moderately to highly painful by participants. The EPPS is a valuable tool for studying pain-related responses, as it gives researchers a choice among many validated pictures depicting different types of pain, increasing the comparability between studies. PERSPECTIVE: This article presents the validation of the experimental pain pictures system, which consists of a set of pain-related pictures. The experimental pain pictures system is composed of pictures depicting different types of pain. Participants rated all the pictures as being negative, arousing, and painful.

The disruptive effects of pain on the early allocation of attentional resources: An attentional blink study

BACKGROUND

Recent evidence suggests that pain dampens attentional processes. However, much of this work has been based on higher-order attentional tasks that involve only spatial attention. Other aspects of the process through which pain engages and holds attention are relatively understudied, in particular, temporal attention. The present set of studies explored how naturally occurring pain (i.e. acute headache) and pain-valenced stimuli affect the ability to recall the second of two targets presented in rapid succession.

METHODS

Across both experiments participants were required to indicate the presence of a predefined probe (T2) and, in the dual task, identify a target (T1). The probe (T2) was placed in three different temporal proximities (ranging from 70 to 1000 ms) following presentation of the target (T1). In Experiment 1, 36 participants completed a task that comprised a rapid stream of letters. Experiment 2 manipulated the threat value, and the complexity, of the stimuli by replacing letters with words. In the dual task condition, T1 was a word from one of four valence categories (neutral, positive, negative, pain).

RESULTS

Being in acute pain reduced the accuracy of identification. This reduction in performance occurred regardless of the temporal positioning of the probe, consistent with previous work that suggests pain has an overall dampening effect. Furthermore, when the valence category of the word was pain-related, T2 accuracy performance was negatively affected.

CONCLUSION

These findings add to the previous evidence that pain has a general dampening effect on attention and that pain-related stimuli are difficult to disengage from.

SIGNIFICANCE

Pain captures attention to allow cognate resources to be directed appropriately in response. However, the temporal effects of this attentional capture are poorly understood. Findings indicate that acute headache pain has a negative impact on participants' performance when identifying the second of two targets presented in close temporal proximity, and that pain-valenced stimuli exacerbate this effect. These findings demonstrate how pain affects early attention and highlights the potential role of disengagement, rather than orientation, of attention in the pain experience.

Attentional Biases Towards Body Expressions of Pain in Men and Women

This study investigated whether there are gender differences in attention to bodily expressions of pain and core emotions. Three experiments are reported using the attentional dot probe task. Images of men and women displaying bodily expressions, including pain, were presented. The task was used to determine whether participants' attention was drawn towards or away from target expressions. Inconsistent evidence was found for an attentional bias towards body expressions, including pain. While biases were affected by gender, patterns varied across the Experiments. Experiment 1, which had a presentation duration of 500 ms, found a relative bias towards the location of male body expressions compared to female expressions. Experiments 2 and 3 varied stimulus exposure times by including both shorter and longer duration conditions (e.g., 100 vs. 500 vs. 1250 ms). In these experiments, a bias towards pain was confirmed. Gender differences were also found, especially in the longer presentation conditions. Expressive body postures captured the attention of women for longer compared to men. These results are discussed in light of their implications for why there are gender differences in attention to pain, and what impact this has on pain behaviour. PERSPECTIVE: We show that men and women might differ in how they direct their attention towards bodily expressions, including pain. These results have relevance to understanding how carers might attend to the pain of others, as well as highlighting the wider role that social-contextual factors have in pain.

Gender differences in attention to pain body postures in a social context: a novel use of the bodies in the crowd task

Pain signals the presence of potential harm, captures attention, and can inhibit performance on concurrent tasks. What is less well known, however, is whether such attentional capture also occurs in a wider social context, such as when observing people in pain. To explore this possibility, we adopted a novel social-cue detection methodology: the bodies-in-the-crowd task. Two experiments are reported that consider whether nonverbal cues of pain, happiness, and anger as expressed through body postures would capture and hold attention. Both experiments recruited 40 (20 male and 20 female) pain-free individuals. Overall, results show that pain postures do not capture attention any more than happiness or anger postures, but disengagement from pain postures was significantly slower across both studies. Gender differences were also found, and were more likely to be found when crowds comprised both men and women. Male pain postures were more likely to capture attention. However, female observers had faster target detection speed, and were quicker to disengage from distractors. They also showed slower disengagement from female expressions overall. Male observers showed no variation based on target or distractor gender. Implications and potential directions for future research are discussed.

The causal role of the somatosensory cortex in prosocial behaviour

Witnessing another person’s suffering elicits vicarious brain activity in areas that are active when we ourselves are in pain. Whether this activity influences prosocial behavior remains the subject of debate. Here participants witnessed a confederate express pain through a reaction of the swatted hand or through a facial expression, and could decide to reduce that pain by donating money. Participants donate more money on trials in which the confederate expressed more pain. Electroencephalography shows that activity of the somatosensory cortex I (SI) hand region explains variance in donation. Transcranial magnetic stimulation (TMS) shows that altering this activity interferes with the pain–donation coupling only when pain is expressed by the hand. High-definition transcranial direct current stimulation (HD-tDCS) shows that altering SI activity also interferes with pain perception. These experiments show that vicarious somatosensory activations contribute to prosocial decision-making and suggest that they do so by helping to transform observed reactions of affected body-parts into accurate perceptions of pain that are necessary for decision-making.

When we experience physical pain, certain areas in our brain that process bodily sensation and emotions switch on. If we see someone else in pain, many of the same regions also get activated. In contrast, convicted criminals with psychopathic traits have less activation in these areas of the brain when witnessing someone’s pain; they also show less empathy and disregard the needs of others. This suggests that a lack of this ‘shared activations’ may lead to problems in empathy. In fact, many scientists believe that shared activations are why we feel empathy for people in pain, and why we are driven to help them. Yet, there is little direct evidence about how the activity in the pain processing parts of the brain actually influences helpful behavior. As a result, some scientists now argue that empathy-related processes may actually contribute very little to helping behavior.

Gallo et al. designed an experiment where participants watched videos of someone having their hand swatted with a belt, and showing different levels of pain as a result. The volunteers could decide to reduce the amount of pain the person received by donating money they could have taken home. The more pain the participants thought the victim was in, the more money they gave up to lessen it. During the study, the activity in the brain region that processes pain in the hand was also measured in the participants. The more active this region was, the more money people donated to help.

Then, Gallo et al. used techniques that interfered with the activity of the brain area involved in perceiving sensations from the hand. This interference changed how accurately participants assessed the victim's pain. It also disrupted the link between donations and the victim's perceived pain: the amount of money people gave no longer matched the level of pain they had witnessed. This suggests that the brain areas that perceive sensations of pain in the self, which evolved primarily to experience our own sensations, also have a social function. They transform the sight of bodily harm into an accurate feeling for how much pain the victim experiences. The findings also show that we need this feeling so we can adapt our help to the needs of others. In the current debate about the role of empathy in helping behaviors, this study demonstrates that empathy-related brain activity indeed promotes helping by allowing us to detect those that need our assistance.

Understanding the relationship between helping behavior and the activity of the brain may further lead to treatments for individuals with antisocial behavior and for children with callous and unemotional traits, a disorder that is associated with a lack of empathy and a general disregard for others.

Social interaction and pain: An arctic expedition

Complex human behaviour can only be understood within its social environment. However, disentangling the causal links between individual outcomes and social network position is empirically challenging. We present a research design in a closed real-world setting with high-resolution temporal data to understand this interplay within a fundamental human experience - physical pain. Study participants completed an isolated 3-week hiking expedition in the Arctic Circle during which they were subject to the same variation in environmental conditions and only interacted amongst themselves. Adolescents provided daily ratings of pain and social interaction partners. Using longitudinal network models, we analyze the interplay between social network position and the experience of pain. Specifically, we test whether experiencing pain is linked to decreasing popularity (increasing isolation), whether adolescents prefer to interact with others experiencing similar pain (homophily), and whether participants are increasingly likely to report similar pain as their interaction partners (contagion). We find that reporting pain is associated with decreasing popularity - interestingly, this effect holds for males only. Further exploratory analyses suggest this is at least partly driven by males withdrawing from contact with females when in pain, enhancing our understanding of pain and masculinity. Contrary to recent experimental and clinical studies, we found no evidence of pain homophily or contagion in the expedition group.

Why Is 10 Past 10 the Default Setting for Clocks and Watches in Advertisements? A Psychological Experiment

Have you ever noticed that in watch advertisements the time is usually set at 10:10? The reasons and psychological effects of this default time setting are elusive. In Experiment 1, we hypothesized that watches showing a time setting resembling a smiling face (10:10) would enhance emotional valence and intention to buy compared to a neutral time setting (11:30), whereas a time setting resembling a sad face (8:20) would have the opposite effect. Moreover, we investigated a possible interaction effect with the gender of the participants. In Experiment 2, we directly tested the hypotheses that watches set at 10:10 resemble a smiling face, whereas watches set at 8:20 resemble a sad face. The data of the first experiment reveal that watches set at 10:10 showed a significant positive effect on the emotion of the observer and the intention to buy. However, watches set at 8:20 did not show any effect on the emotion or the intention to buy. Moreover, watches set at 10:10 induced in women significantly stronger ratings of pleasure than in men. The data of the second experiment show that participants consistently perceive high resemblance between watches set at 10:10 and a smiling face as well as high resemblance between watches set at 8:20 and a sad face. This study provides for the first time empirical evidence for the notion that using watches with a time setting resembling a smiling face (like 10:10) can positively affect the emotional response of the observers and their evaluation of a seen watch, even though they are not aware of the fact that the shown time setting is inducing this effect. Practical implications of the observed findings and alternative explanations are discussed.