Touch and personality: extraversion predicts somatosensory brain response

Surfing the OCEAN: The machine learning psycholexical approach 2.0 to detect personality traits in texts

OBJECTIVE

We aimed to develop a machine learning model to infer OCEAN traits from text.

BACKGROUND

The psycholexical approach allows retrieving information about personality traits from human language. However, it has rarely been applied because of methodological and practical issues that current computational advancements could overcome.

METHOD

Classical taxonomies and a large Yelp corpus were leveraged to learn an embedding for each personality trait. These embeddings were used to train a feedforward neural network for predicting trait values. Their generalization performances have been evaluated through two external validation studies involving experts (N = 11) and laypeople (N = 100) in a discrimination task about the best markers of each trait and polarity.

RESULTS

Intrinsic validation of the model yielded excellent results, with R2 values greater than 0.78. The validation studies showed a high proportion of matches between participants' choices and model predictions, confirming its efficacy in identifying new terms related to the OCEAN traits. The best performance was observed for agreeableness and extraversion, especially for their positive polarities. The model was less efficient in identifying the negative polarity of openness and conscientiousness.

CONCLUSIONS

This innovative methodology can be considered a "psycholexical approach 2.0," contributing to research in personality and its practical applications in many fields.

Trajectories and determinants of acute stress disorder during the COVID-19 centralized quarantine: A latent class growth analysis

COVID-19 centralized quarantine may cause acute stress disorder (ASD). However, it is unknown how individuals present heterogeneous ASD trajectories during the COVID-19 centralized quarantine and what factors contribute to these patterns. This study aimed to identify the ASD trajectories and their determinants during the centralized quarantine period, and the mediating effects of resilience on these associations. A longitudinal survey with three waves was conducted in a randomly selected quarantine hotel in Shenzhen, China from October to November 2020. A total of 273 participants completed online measures assessing ASD symptoms, Eysenck's personality constructs of extraversion (E), neuroticism (N), psychoticism (P), and resilience on Day 1, and reported ASD symptoms on Days 7 and 14 during their 14-day centralized quarantine periods. Latent class growth analysis identified three trajectories: constantly high symptoms (CHS, 4.76%), decreasing symptoms (DS, 11.72%), and constantly low symptoms (CLS, 83.52%). The CHS and DS subgroups both reported lower E and higher N scores, but not P, compared with the CLS subgroup. Resilience mediated the effects of three personality constructs on ASD trajectories, except for the association between N and DS membership. Our study highlights the heterogeneity in stress responses to the COVID-19 centralized quarantine. The high-risk subgroup with persistent ASD symptoms was characterized by lower E and higher N. The resilience process accounted for the effects of personality in shaping distinct ASD trajectories. Our findings have implications to detect the populations vulnerable to ASD and provide insights for developing timely resilience enhancement intervention programs.

Multiple sclerosis and personality traits: associations with depression and anxiety

BACKGROUND

Depression and anxiety are commonly observed in people with multiple sclerosis (pwMS). There is a growing body of literature supporting the hypothesis that personality traits can influence the mood disorders. This study aimed to investigate the personality traits and their relationships with depression and anxiety among pwMS.

METHODS

234 pwMS were involved in this cross-sectional study. Personality traits, depression, and anxiety were assessed using the NEO Five-Factor Inventory (NEO-FFI) and Hospital Anxiety and Depression Scale (HADS), respectively. Pearson's correlation coefficient and generalized linear model were employed to evaluate the relationships between demographic and clinical characteristics, NEO-FFI, and HADS subscales.

RESULTS

In pwMS, longer disease duration was significantly associated with lower level of conscientiousness (β = - 0.23, p = 0.008) and agreeableness (β = - 0.2, p = 0.01). Moreover, higher expanded disability status scale (EDSS) of pwMS had a significant relationship with higher level of neuroticism (β = 0.89, p = 0.01). Increased level of neuroticism was significantly correlated with lower level of extraversion (r = - 0.28, p < 0.001), openness (r = - 0.37, p < 0.001), agreeableness (r = - 0.31, p < 0.001), and conscientiousness (r = - 0.45, p < 0.001). PwMS with higher level of conscientiousness showed more extraversion (r = 0.23, p < 0.001), openness (r = 0.61, p < 0.001), and agreeableness (r = 0.41, p < 0.001). Elevated level of neuroticism was significantly associated with higher level of anxiety (β = 0.47, p < 0.001) and depression (β = 0.11, p < 0.001) among pwMS.

CONCLUSION

The co-occurrence of depression and anxiety is probably associated with neuroticism among pwMS. Additionally, the impact of personality traits extends to influencing key disease aspects such as physical disability and disease duration in MS.

Social Touch: Its Mirror-like Responses and Implications in Neurological and Psychiatric Diseases

What is the significance of a touch encoded by slow-conducted unmyelinated C-tactile (CT) fibers? It is the so-called affiliative touch, which has a fundamental social impact. In humans, it has been demonstrated that the affiliative valence of this kind of touch is encoded by a dedicated central network, not involved in the encoding of discriminative touch, namely, the "social brain". Moreover, CT-related touch has significant consequences on the human autonomic system, not present in the case of discriminative touch, which does not involve CT fibers as the modulation of vagal tone. In addition, CT-related touch provokes central effects as well. An interesting finding is that CT-related touch can elicit "mirror-like responses" since there is evidence that we would have the same perception of a caress regardless of whether it would be felt or seen and that the same brain areas would be activated. Information from CT afferents in the posterior insular cortex likely provides a basis for encoding observed caresses. We also explored the application of this kind of touch in unphysiological conditions and in premature newborns. In the present literature review, we aim to (1) examine the effects of CT-related touch at autonomic and central levels and (2) highlight CT-related touch and mirror networks, seeking to draw a line of connection between them. Finally, the review aims to give an overview of the involvement of the CT system in some neurologic and psychiatric diseases.

Social touch in the age of computational ethology: Embracing as a multidimensional and complex behaviour

Social affective touch is an important aspect of close relationships in humans. It has been also observed in many non-human primate species. Despite the high relevance of behaviours like embraces for personal wellbeing and mental health, they remain vastly under-investigated in psychology. This may be because psychology often relies on a limited repertoire of behavioural measurements such as error rates and reaction time measurements. These are, however, insufficient to capture the multidimensional complexity of highly interactive dyadic behaviours like embraces. Based on recent advances in computational ethology in animal models, the rapidly emerging field of human computational ethology utilizes an accessible repertoire of machine learning methods to track and quantify complex natural behaviours. We highlight how such techniques can be utilized to investigate social touch and which preliminary conditions, motor aspects and higher-level interactions need to be considered. Ultimately, integration of computational ethology with mobile neuroscience techniques such as ultraportable EEG systems will allow for an ecologically valid investigation of social affective touch in humans that will advance psychological research of emotions.

Children's vicarious ratings of social touch are tuned to the velocity but not the location of a caress

Affective sharing is a bottom-up process involving automatic processing of sensory inputs that facilitate vicarious experience of another's emotional state. It is grounded directly in the prior experiences of the perceiver. In adults, vicarious ratings of affective touch match the known velocity tuning and hypothesised anatomical distribution of C-tactile afferents (CT), a subclass of C-fibre which respond preferentially to low force/velocity stroking touch, typically perceived as pleasant. Given the centrality of touch to early nurturing interactions, here we examined whether primary school aged children's vicarious ratings of affective touch show the same anatomical and velocity specific patterns reported in adults. Forty-four children aged between 8 and 11 (mean age 9, 24 male) rated a sequence of video clips depicting one individual being touched by another on 5 different upper-body sites (palm, dorsal forearm, ventral forearm, upper-arm and back) at 3 different velocities (static, CT optimal, slow stroking and non-CT optimal, fast stroking). Immediately after viewing each clip, participants were asked to rate how pleasant they perceived the touch to be. While children rated the CT optimal velocity significantly higher than static or non-CT optimal touch, unlike adults their ratings did not vary across skin sites. This difference may reflect the fact children's ratings are grounded in bottom-up affective resonance while adults also draw on top-down cognitive evaluation of the broader social context when rating the stimuli.

Dispositional empathy predicts primary somatosensory cortex activity while receiving touch by a hand

Previous research revealed an active network of brain areas such as insula and anterior cingulate cortex when witnessing somebody else in pain and feeling empathy. But numerous studies also suggested a role of the somatosensory cortices for state and trait empathy. While recent studies highlight the role of the observer’s primary somatosensory cortex when seeing painful or nonpainful touch, the interaction of somatosensory cortex activity with empathy when receiving touch on the own body is unknown. The current study examines the relationship of touch related somatosensory cortex activity with dispositional empathy by employing an fMRI approach. Participants were touched on the palm of the hand either by the hand of an experimenter or by a rubber hand. We found that the BOLD responses in the primary somatosensory cortex were associated with empathy personality traits personal distress and perspective taking. This relationship was observed when participants were touched both with the experimenter’s real hand or a rubber hand. What is the reason for this link between touch perception and trait empathy? We argue that more empathic individuals may express stronger attention both to other’s human perceptions as well as to the own sensations. In this way, higher dispositional empathy levels might enhance tactile processing by top-down processes. We discuss possible implications of these findings.

Keeping "In Touch": Demographic Patterns of Interpersonal Touch in Later Life

Touch is an important element of human social interaction linked to various dimensions of well-being, but we know little of how it is distributed among older adults. This study considers whether greeting/affectionate touch is a function of characteristics such as race, gender, and socioeconomic status. Data come from Wave 1 (2005-2006) of the NSHAP study from the United States. Results reveal that women experienced more frequent touch relative to men, net of several features of the interpersonal environment. Mediation analyses revealed that gender differences in associations with touch were partially explained by women's greater participation in formal and informal social activity. No patterns were detected related to race, education, or wealth. This study situates greeting/affectionate touch as a form of corporeal non-verbal interaction that offers a unique lens into patterns of social connection. We close by considering what this form of interaction means in the wake of the COVID-19 pandemic.

Relationship between Personality and Biological Reactivity to Stress: A Review

Objective Personality traits can be the basis for individual differences in the biological response of stress. To date, many psychobiological studies have been conducted to clarify the relationship between personality and biological reactivity to stress. This review summarizes the most important findings in this area of research. Results Key findings related to the relationship between personality factors and stress-sensitive biological systems in four research models have been summarized; model of psychosocial characteristics, model based on Rumination and Emotional Inhibition, Eysenck's biopsychological model, and Five-Factor Approach of Personality. Conclusion According to the results of this review, it can be concluded that personality typology of individuals influenced their biological reactivity to stressful events. Understanding the biological basis of personality can help to better understand vulnerability to stress. Future research can be continuing based on framework of the four models.

Unisensory and multisensory Self-referential stimulation of the lower limb: An exploratory fMRI study on healthy subjects

BACKGROUND

The holistic view of the person is the essence of the physiotherapy. Knowledge of approaches that develop the whole person promotes better patient outcomes. Multisensory Self-referential stimulation, more than a unisensory one, seems to produce a holistic experience of the Self ("Core-Self").

OBJECTIVES

(1) To analyze the somatotopic brain activation during unisensory and multisensorial Self-referential stimulus; and (2) to understand if the areas activated by multisensorial Self-referential stimulation are the ones responsible for the "Core-Self."

METHODS

An exploratory functional magnetic resonance imaging (fMRI) study was performed with 10 healthy subjects, under the stimulation of the lower limbs with three Self-referential stimuli: unisensory auditory-verbal, unisensory tactile-manual, and multisensory, applying the unisensory stimuli simultaneously.

RESULTS

Unisensory stimulation elicits bilateral activations of the temporoparietal junction (TPJ), of the primary somatosensory cortex (S1), of the primary motor cortex (BA4), of the premotor cortex (BA6) and of BA44; multisensory stimulation also elicits activity in TPJ, BA4, and BA6, and when compared with unisensory stimuli, activations were found in: (1) Cortical and subcortical midline structures-BA7 (precuneus), BA9 (medial prefrontal cortex), BA30 (posterior cingulated), superior colliculum and posterior cerebellum; and (2) Posterior lateral cortex-TPJ, posterior BA13 (insula), BA19, and BA37. Bilateral TPJ is the one that showed the biggest activation volume.

CONCLUSION

This specific multisensory stimulation produces a brain activation map in regions that are responsible for multisensory Self-processing and may represent the Core-Self. We recommend the use of this specific multisensory stimulation as a physiotherapy intervention strategy that might promote the Self-reorganization.

The social brain: neurobiological basis of affiliative behaviours and psychological well-being

The social brain hypothesis proposes that the demands of the social environment provided the evolutionary pressure that led to the expansion of the primate brain. Consistent with this notion, that functioning in the social world is crucial to our survival, while close supportive relationships are known to enhance well-being, a range of social stressors such as abuse, discrimination and dysfunctional relationships can increase the risk of psychiatric disorders. The centrality of the social world to our everyday lives is further exemplified by the fact that abnormality in social behaviour is a salient feature of a range of neurodevelopmental and psychiatric disorders. This paper aims to provide a selective overview of current knowledge of the neurobiological basis of our ability to form and maintain close personal relationships, and of the benefits these relationships confer on our health. Focusing on neurochemical and neuroendocrine interactions within affective and motivational neural circuits, it highlights the specific importance of cutaneous somatosensation in affiliative behaviours and psychological well-being and reviews evidence, in support of the hypothesis, that a class of cutaneous unmyelinated, low threshold mechanosensitive nerves, named c-tactile afferents, have a direct and specific role in processing affiliative tactile stimuli.

Mirror-like brain responses to observed touch and personality dimensions

The last years have shown a growing interest in research on the neural mechanisms for perceiving and understanding social interactions. Only very recently, a role for somatosensation in social perception has been suggested. Numerous studies reported vicarious responses in the primary somatosensory cortex (SI) and other areas merely when seeing others being touched. Moreover, it has been demonstrated that these vicarious somatosensory responses can be linked with inter-individual differences in empathy. However, beyond empathy other personality traits have been shown to interact with social perception and behavior. Here we tested if personality traits according to the Five-Factor-Model interact with vicarious activation in somatosensory brain regions. We conducted a functional magnetic resonance imaging (fMRI) study in which subjects viewed video clips showing simple non-painful touch to a hand and a control condition including the same visual and motion parts. Results revealed vicarious somatosensory activation when viewing the touched hand, as expected. Vicarious activation in SI showed a trend for a positive correlation with the personality trait openness to experience. Moreover, mirror-like responses in the insula were strongly correlated with the personality trait conscientiousness, suggesting links to processes of self-control. We conclude that vicarious brain responses to seen touch seem to interact with personality traits.

Understanding others' feelings: the role of the right primary somatosensory cortex in encoding the affective valence of others' touch

Brain imaging studies in humans have shown the existence of a shared somatosensory representation in the primary somatosensory cortex (S1), putatively involved in understanding others' sensations (Keysers et al., 2010); however, the role of S1 in such a high-level process is still unknown. To ascertain the causal involvement of S1, and its possible hemispheric lateralization, in encoding the affective valence of emotional scenes, depicting, or not, a tactile event, we gave to healthy participants a picture-based affective go/no-go task and low-frequency repetitive transcranial magnetic stimulation (rTMS). The dorsolateral prefrontal cortex (DLPFC) was chosen as control site. rTMS over the right, but not the left, S1 selectively increased the participants' latencies in the affective go/no-go task, but only when the affective state was conveyed by touch; intriguingly, this interfering effect was associated with the empathic ability to adopt the subjective perspective of others. The left, not the right, DLPFC is also involved in affective go/no-go performance, but regardless of the sight of touch, and independently of empathic abilities. This novel evidence demonstrates the crossmodal role of right S1 in encoding the pleasant and aversive consequences of others' sensations evoked by touch.

The human somatosensory system: from perception to decision making

Pioneering human and animal research has yielded a better understanding of the brain networks involved in somatosensory perception and decision making. New methodical achievements in combination with computational formalization allow research questions to be addressed which increasingly reflect not only the complex sensory demands of real environments, but also the cognitive ones. Here, we review the latest research on somatosensory perception and decision making with a special focus on the recruitment of supplementary brain networks which are dependent on the situation-associated sensory and cognitive demands. We also refer to literature on sensory-motor integration processes during visual decision making to delineate the complexity and dynamics of how sensory information is relayed to the motor output system. Finally, we review the latest literature which provides novel evidence that other everyday life situations, such as semantic decision making or social interactions, appear to depend on tactile experiences; suggesting that the sense of touch, being the first sense to develop ontogenetically, may essentially support later development of other conceptual knowledge.