Interpersonal touch suppresses visual processing of aversive stimuli

Tactile Interaction with a Humanoid Robot: Effects on Physiology and Subjective Impressions

This study investigated how touching and being touched by a humanoid robot affects human physiology, impressions of the interaction, and attitudes towards humanoid robots. 21 healthy adult participants completed a 3 (touch style: touching, being touched, pointing) × 2 (body part: hand vs buttock) within-subject design using a Pepper robot. Skin conductance response (SCR) was measured during each interaction. Perceived impressions of the interaction (i.e., friendliness, comfort, arousal) were measured per questionnaire after each interaction. Participants’ demographics and their attitude towards robots were also considered. We found shorter SCR rise times in the being touched compared to the touching condition, possibly reflecting psychological alertness to the unpredictability of robot-initiated contacts. The hand condition had shorter rise times than the buttock condition. Most participants evaluated the hand condition as most friendly and comfortable and the robot-initiated interactions as most arousing. Interacting with Pepper improved attitudes towards robots. Our findings require future studies with larger samples and improved procedures. They have implications for robot design in all domains involving tactile interactions, such as caring and intimacy.

Physical correlates of human-like softness elicit high tactile pleasantness

Touching an object can elicit affective sensations. Because these sensations are critical for social interaction, tactile preferences may be adapted to the characteristics of the human body. We have previously shown that compliance, a physical correlate of softness, increased the tactile pleasantness of a deformable surface. However, the extent to which object compliance similar to the human body elicits tactile pleasantness remains unknown. We addressed this question by using a wide range of compliances and by measuring the distribution of compliance of human body parts. The participants numerically estimated the perceived pleasantness or softness while pushing tactile stimuli with their right index fingers. The perceived softness monotonically increased with increasing compliance and then leveled off around the end of the stimulus range. By contrast, pleasantness showed an inverse U pattern as a function of compliance, reaching the maximum between 5 and 7 mm/N. This range of compliance was within that for both hand and arm. These results indicate that objects with similar compliance levels as those of human body parts yield the highest pleasantness when pushing them.

With a little help from my friends: The effect of social proximity on emotion regulation-related brain activity

When experiencing negative emotions, individuals often reach out for social support to help regulate their emotions. In times of an acute crisis, however, close friends might not be available, and physical closeness might be impossible. This functional magnetic resonance imaging (fMRI) study investigated the effect of social proximity on the effectiveness of social support for regulating emotions and the underlying neural mechanisms. Participants regulated their emotions in response to negative images either alone (intrapersonal regulation), or with help of a picture and supporting sentence provided by the best friend, or by a stranger (interpersonal regulation). Regulation success was enhanced for the support of friends compared to regulating alone or with the support of strangers. This effect was accompanied by the interplay of large-scale brain networks involved in processing emotions, social cognition, and cognitive control. Interpersonal regulation appeared to be implemented by lateral prefrontal regions. The amygdala showed increased activation for strangers. The activation profile of the social cognition network suggests a role in supporting empathic and mentalizing processes. The results highlight the power of social connectedness for boosting emotion regulation ability and the different neural networks that contribute to this effect.

Calming Effects of Touch in Human, Animal, and Robotic Interaction-Scientific State-of-the-Art and Technical Advances

Small everyday gestures such as a tap on the shoulder can affect the way humans feel and act. Touch can have a calming effect and alter the way stress is handled, thereby promoting mental and physical health. Due to current technical advances and the growing role of intelligent robots in households and healthcare, recent research also addressed the potential of robotic touch for stress reduction. In addition, touch by non-human agents such as animals or inanimate objects may have a calming effect. This conceptual article will review a selection of the most relevant studies reporting the physiological, hormonal, neural, and subjective effects of touch on stress, arousal, and negative affect. Robotic systems capable of non-social touch will be assessed together with control strategies and sensor technologies. Parallels and differences of human-to-human touch and human-to-non-human touch will be discussed. We propose that, under appropriate conditions, touch can act as (social) signal for safety, even when the interaction partner is an animal or a machine. We will also outline potential directions for future research and clinical relevance. Thereby, this review can provide a foundation for further investigations into the beneficial contribution of touch by different agents to regulate negative affect and arousal in humans.

Tactile perception of pleasantness in relation to perceived softness

The sense of touch allows us to infer objects’ physical properties, while the same input also produces affective sensations. These affective sensations are important for interpersonal relationships and personal well-being, which raises the possibility that tactile preferences are adapted to the characteristics of the skin. Previous studies examined how physical properties such as surface roughness and temperature influence affective sensations; however, little is known about the effect of compliance (physical correlate of softness) on pleasantness. Thus, we investigated the psychophysical link between softness and pleasantness. Pieces of human skin-like rubber with different compliances were pressed against participants’ fingers. Two groups of participants numerically estimated the perceived magnitude of either pleasantness or softness. The perceived magnitude of pleasantness and softness both increased monotonically as a function of increasing object compliance, levelling off at around the end of the stimulus range. However, inter-subject variability was greater for pleasantness than for perceived softness, whereas the slope of the linear function fit to the magnitude estimates was steeper for softness than for pleasantness. These results indicate that object compliance is a critical physical determinant for pleasantness, whereas the effect of compliance on pleasantness was more variable among individuals than the effect on softness was.

Cross-cultural similarity in relationship-specific social touching

Many species use touching for reinforcing social structures, and particularly, non-human primates use social grooming for managing their social networks. However, it is still unclear how social touch contributes to the maintenance and reinforcement of human social networks. Human studies in Western cultures suggest that the body locations where touch is allowed are associated with the strength of the emotional bond between the person touched and the toucher. However, it is unknown to what extent this relationship is culturally universal and generalizes to non-Western cultures. Here, we compared relationship-specific, bodily touch allowance maps across one Western (N = 386, UK) and one East Asian (N = 255, Japan) country. In both cultures, the strength of the emotional bond was linearly associated with permissible touch area. However, Western participants experienced social touching as more pleasurable than Asian participants. These results indicate a similarity of emotional bonding via social touch between East Asian and Western cultures.

A systematic review of structural and functional MRI studies on pain catastrophizing

Objectives: Pain catastrophizing is reliably associated with pain reports during experimental pain in healthy, pain-free subjects and in people with chronic pain. It also correlates with self-reports of clinical pain intensity/severity in a variety of disorders characterized by chronic pain in adults, adolescents and children. However, processes, through which it exerts its effects are yet unclear. In this paper, our primary aim was to synthesize neuroimaging research to open a window to possible mechanisms underlying pain catastrophizing in both chronic pain patients and healthy controls. We also aimed to compare whether the neural correlates of pain catastrophizing are similar in these two groups.

Methods: PubMed and the Web of Science were searched for magnetic resonance imaging (MRI) studies that explored neural correlates of pain catastrophizing.

Results: Twenty articles met the inclusion criteria. The results of our review show a connection between pain catastrophizing and brain areas tightly connected to pain perception (including the somatosensory cortices, anterior insula, anterior cingulate cortex and thalamus) and/or modulation (eg, the dorsolateral prefrontal cortex). Our results also highlight that these processes - in relation to pain catastrophizing - are more pronounced in chronic pain patients, suggesting that structural and functional brain alterations (and perhaps mechanisms) related to pain catastrophizing may depend on prior and/or relatively stable/constant pain experience. However, we also found methodological issues and differences that could lead to divergent results.

Discussion: Based on our results, pain catastrophizing might be related to salience detection, pain processing, and top-down attentional processes. More research is recommended to explore neural changes to specific types of catastrophizing thoughts (eg, experimentally induced and/or state). Furthermore, we provide ideas regarding pain catastrophizing studies in the future for a more standardized approach.

Brain networks require a network-conscious psychopathological approach

In experimental psychology and neuroscience, technological advances and multisensory research have contributed to gradually dismiss a version of reductionism. Empirical results no longer support a brain model in which distinct "modules" perform discrete functions, but rather, a brain of partially overlapping networks. A similarly changed brain model is extending to psychopathology and clinical psychology, and partly accounts for the problems of reductionism.

Social domain based modulation of neural responses to threat: The different roles of romantic partners versus friends

The neural circuitry associated with threat regulation in the absence of other people is well established. An examination of threat regulatory processes with people from different domains of an individual's social world is key to understanding social emotion regulation and personality functioning conceptualised as social domain organisation. In this study, 42 healthy female participants completed functional magnetic imaging sessions in which they underwent a scan in the presence of a romantic partner or friend, whilst completing a threat of shock task. In the presence of a romantic partner vs. friend, we found a reduction in amygdala activation to threat vs. safe trials over time. Furthermore, in the presence of a romantic partner vs. friend we observed greater subgenual anterior cingulate cortex and ventromedial prefrontal cortex activation to threat vs. safe trials overall. The results support the hypothesis that recruitment of threat regulation circuitry is modulated by romantic partner relative to another person well-known to the individual. Future work needs to examine neural responses to a wider range of stimuli across more social domains, and implications of failures of this neural organisation for psychopathology.

Association between salivary serotonin and the social sharing of happiness

Although human saliva contains the monoamine serotonin, which plays a key role in the modulation of emotional states, the association between salivary serotonin and empathic ability remains unclear. In order to elucidate the associations between salivary serotonin levels, trait empathy, and the sharing effect of emotions (i.e., sharing emotional experiences with others), we performed a vignette-based study. Participants were asked to evaluate their happiness when they experience several hypothetical life events, whereby we manipulated the valence of the imagined event (positive, neutral, or negative), as well as the presence of a friend (absent, positive, or negative). Results indicated that the presence of a happy friend significantly enhanced participants’ happiness. Correlation analysis demonstrated that salivary serotonin levels were negatively correlated with happiness when both the self and friend conditions were positive. Correlation analysis also indicated a negative relationship between salivary serotonin levels and trait empathy (particularly in perspective taking), which was measured by the Interpersonal Reactivity Index. Furthermore, an exploratory multiple regression analysis suggested that mothers’ attention during childhood predicted salivary serotonin levels. Our findings indicate that empathic abilities and the social sharing of happiness decreases as a function of salivary serotonin levels.

Being in a Romantic Relationship Is Associated with Reduced Gray Matter Density in Striatum and Increased Subjective Happiness

Romantic relationship, a widespread feature of human society, is one of the most influential factors in daily life. Although stimuli related to romantic love or being in a romantic relationship commonly result in enhancement of activation or functional connectivity of the reward system, including the striatum, the structure underlying romantic relationship-related regions remain unclear. Because individual experiences can alter gray matter within the adult human brain, we hypothesized that romantic relationship is associated with structural differences in the striatum related to the positive subjective experience of being in a romantic relationship. Because intimate romantic relationships contribute to perceived subjective happiness, this subjective enhancement of happiness might be accompanied by the experience of positive events related to being in a romantic relationship. To test this hypothesis and elucidate the structure involved, we compared subjective happiness, an indirect measure of the existence of positive experiences caused by being in a romantic relationship, of participants with or without romantic partners (N = 68). Furthermore, we also conducted a voxel-based morphometry study of the effects of being in a romantic relationship (N = 113). Being in a romantic relationship was associated with greater subjective happiness and reduced gray matter density within the right dorsal striatum. These results suggest that being in a romantic relationship enhances perceived subjective happiness via positive experiences. Furthermore, the observed reduction in gray matter density in the right dorsal striatum may reflect an increase in saliency of social reward within a romantic relationship. Thus, being in a romantic relationship is associated with positive experiences and a reduction of gray matter density in the right dorsal striatum, representing a modulation of social reward.