Touch Perception Research Articles

Alternatives to Friction Coefficient: Fine Touch Perception Relies on Frictional Instabilities.

Fine touch perception is often correlated to material properties and friction coefficients, but the inherent variability of human motion has led to low correlations and contradictory findings. Instead, we hypothesized that humans use frictional instabilities to discriminate between objects. We constructed a set of coated surfaces with physical differences which were imperceptible by touch but created different types of instabilities based on how quickly a finger is slid and how hard a human finger is pressed during sliding. We found that participant accuracy in tactile discrimination most strongly correlated with formations of steady sliding, and response times negatively correlated with stiction spikes. Conversely, traditional metrics like surface roughness or average friction coefficient did not predict tactile discriminability. Identifying the central role of frictional instabilities as an alternative to using friction coefficients should accelerate the design of tactile interfaces for psychophysics and haptics.

Long-term subjective and objective outcomes after digital nerve repair: a cohort study.

Digital nerve injuries are common, but few studies report long-term effects for the individual. The primary aim of this matched-pairs study comparing digital nerve injuries in border digits or central fingers was to investigate hand function 3-10 years after digital nerve repair, assessed using the Mini Sollerman test in 86 patients. Secondary outcomes were sensory function, range of motion, grip strength and patient-reported measures. No significant difference was seen in hand function between the groups, except for lower grip strength in patients with central finger injury. Tactile discrimination was achieved in 87%, with best results among participants aged less than 44 years. Touch perception was measurable in 99%. No statistically significant differences in sensory function were found between the groups. Patient-reported disability was low, with median Quick Disabilities of the Arm, Shoulder and Hand score of 5, but half of the patients reported neuropathic pain. Numbness and cold sensitivity were the symptoms graded worst after digital nerve injury.Level of evidence: III.

In-situ cured gel polymer/ecoflex hierarchical structure-based stretchable and robust TENG for intelligent touch perception and biometric recognition

Gel-based sensors for next generation touch panels have been acknowledged for their exceptional sensitivity and flexibility. However, these sensors typically depend on a metal grid connection, which is susceptible to structural deformation under heavy stress applications and necessitates external power. Here, we report a novel in-situ cured gel polymer electrode-based triboelectric nanogenerator (GPE-TENG) that is stretchable, semi-transparent, and durable, designed to enable a self-powered touch panel for intelligent touch perception. The in-situ curing of the hierarchical structure of the ionic polymer gel encapsulated within the ecoflex ensures robust adhesion of the ionic conductive polymer gel (PEO/LiTFSI) to the ecoflex layers, addressing the issue of delamination in TENG components under mechanical stress. As a result, the GPE-TENG demonstrates high durability, enduring under stretching of approximately 375 % and sustaining heavy mechanical deformations (under folding, twisting, and rolling) over a long period (approximately 2 months) without loss of functionality. Remarkably, the GPE-TENG exhibits outstanding energy harvesting capabilities with a peak power density of 0.36 W m-2. Notably, the GPE-TENG generates electrical signals through simple device stretching, thus serving as a self-powered wearable sensor for human activity monitoring. Moreover, a 9-digital arrayed (3 × 3) flexible, semi-transparent, and self-powered touch panel based on the GPE-TENG shows multifunctionality, including touch track/pattern recognition (i.e. touch and sliding mode) and a highly accurate (∼98 %) deep learning assisted smart biometric system for user identification.

Interventions for people with perceptual disorders after stroke: the PIONEER scoping review, Cochrane systematic review and priority setting project.

Stroke often affects recognition and interpretation of information from our senses, resulting in perceptual disorders. Evidence to inform treatment is unclear. To determine the breadth and effectiveness of interventions for stroke-related perceptual disorders and identify priority research questions. We undertook a scoping review and then Cochrane systematic review. Definitions, outcome prioritisation, data interpretation and research prioritisation were coproduced with people who had perceptual disorders post stroke and healthcare professionals. We systematically searched electronic databases (including MEDLINE, EMBASE, inception to August 2021) and grey literature. We included studies (any design) of interventions for people with hearing, smell, somatosensation, taste, touch or visual perception disorders following stroke. Abstracts and full texts were independently dual reviewed. Data were tabulated, synthesised narratively and mapped by availability, sense and interventions. Research quality was not evaluated. Our Cochrane review synthesised the randomised controlled trial data, evaluated risk of bias (including randomisation, blinding, reporting) and meta-analysed intervention comparisons (vs. controls or no treatment) using RevMan 5.4. We judged certainty of evidence using grading of recommendations, assessment, development and evaluation. Activities of daily living after treatment was our primary outcome. Extended activities of daily living, quality of life, mental health and psychological well-being perceptual functional and adverse event data were also extracted. We included 80 studies (n = 893): case studies (36/80) and randomised controlled trials (22/80). No stroke survivor or family stakeholder involvement was reported. Studies addressed visual (42.5%, 34/80), somatosensation (35%, 28/80), auditory (8.7%, 7/80) and tactile (7.5%, 6/80) perceptual disorders; some studies focused on 'mixed perceptual disorders' (6.2%, 5/80 such as taste-smell disorders). We identified 93 pharmacological, non-invasive brain stimulation or rehabilitation (restitution, substitution, compensation or mixed) interventions. Details were limited. Studies commonly measured perceptual (75%, 60/80), motor-sensorimotor (40%, 32/80) activities of daily living (22.5%, 18/80) or sensory function (15%, 12/80) outcomes. We included 18 randomised controlled trials (n = 541) addressing tactile (3 randomised controlled trials; n = 70), somatosensory (7 randomised controlled trials; n = 196), visual (7 randomised controlled trials; n = 225) and mixed tactile-somatosensory (1 randomised controlled trial; n = 50) disorders. None addressed hearing, taste or smell disorders. One non-invasive brain stimulation, one compensation, 25 restitution and 4 mixed interventions were described. Risk of bias was low for random sequence generation (13/18), attrition (14/18) and outcome reporting (16/18). Perception was the most commonly measured outcome (11 randomised controlled trials); only 7 randomised controlled trials measured activities of daily living. Limited data provided insufficient evidence to determine the effectiveness of any intervention. Confidence in the evidence was low-very low. Our clinical (n = 4) and lived experience (n = 5) experts contributed throughout the project, coproducing a list of clinical implications and research priorities. Top research priorities included exploring the impact of, assessment of, and interventions for post-stroke perceptual disorders. Results are limited by the small number of studies identified and the small sample sizes, with a high proportion of single-participant studies. There was limited description of the perceptual disorders and intervention(s) evaluated. Few studies measured outcomes relating to functional impacts. There was limited investigation of hearing, smell, taste and touch perception disorders. Evidence informing interventions for perceptual disorders after stroke is limited for all senses. Further research, including high-quality randomised controlled trials, to inform clinical practice are required. This study is registered as PROSPERO CRD42019160270. This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: NIHR128829) and is published in full in Health Technology Assessment; Vol. 28, No. 69. See the NIHR Funding and Awards Website for further award information.

Artificial embodiment displaces cortical neuromagnetic somatosensory responses

Integrating artificial limbs as part of one's body involves complex neuroplastic changes resulting from various sensory inputs. While somatosensory feedback is crucial, plastic processes that enable embodiment remain unknown. We investigated this using somatosensory evoked fields (SEFs) in the primary somatosensory cortex (S1) following the Rubber Hand Illusion (RHI), known to quickly induce artificial limb embodiment. During electrical stimulation of the little finger and thumb, 19 adults underwent neuromagnetic recordings before and after the RHI. We found early SEF displacement, including an illusion-brain correlation between extent of embodiment and specific changes to the first cortical response at 20 ms in Area 3b, within S1. Furthermore, we observed a posteriorly directed displacement at 35 ms towards Area 1, known to be important for visual integration during touch perception. That this second displacement was unrelated to extent of embodiment implies a functional distinction between neuroplastic changes of these components and areas. The earlier shift in Area 3b may shape extent of limb ownership, while subsequent displacement into Area 1 may relate to early visual-tactile integration that initiates embodiment. Here we provide evidence for multiple neuroplastic processes in S1—lasting beyond the illusion—supporting integration of artificial limbs like prostheses within the body representation.

Measuring differences in social touch: Development and validation of the short Touch Experiences and Attitudes Questionnaire (TEAQ-s)

Interpersonal touch is an essential part of human social life, impacting emotional and physical well-being. Variations in touch behavior and perception can be assessed by the Touch Experiences and Attitudes Questionnaire (TEAQ). Although comprehensive, the TEAQ appears lengthy with 57 items, limiting its usability for large surveys. Therefore, we developed a refined and shortened version of 16 items, tested in Germany and France. This manuscript presents three studies. In the first, we created the TEAQ-s (n = 313). In the second and third, we validated the TEAQ-s in German (n = 383) and French (n = 327), respectively. The resulting TEAQ-s showed strong reliability (Cronbach's alpha: 0.86 to 0.87; test-retest correlation: r = 0.85) and validity consistent with the original version. Analyses also revealed that being in a relationship, relationship satisfaction, mental health, and body appreciation were positively related to touch experiences and attitudes. A four-factor structure (4 items per scale) was confirmed through factor analysis. Final subscales are attitude to friendly touch, current intimate touch, childhood touch, and attitude to intimate touch. We hope that the TEAQ-s serves as a valuable tool for researchers in the field of touch and beyond, offering well-founded items in an efficient format.

Surgical refinements and sensory and functional outcomes of using thinned sensate anterolateral thigh perforator flaps for foot and ankle reconstruction: A retrospective study.

To improve the use of sensate anterolateral thigh (ALT) flaps for foot and ankle reconstruction, we employed a thinned nerve-selective harvesting technique. The data of 31 patients in whom sensate ALT perforator flaps were transferred for reconstruction of soft-tissue defects in the foot and ankle were reviewed. Flaps were elevated with 2 refinements. The first is the initial selection of the "true" sensory branch in the medial incision on the suprafascial plane. The second is flap thinning by keeping a cuff of thin deep fat surrounding the point where the perforator or nerve branch inserts into the superficial fat layer. The recipient site assessment consisted of complications, monofilament touch perception, sharp-blunt discrimination, axial circumference, and American Orthopedic Foot and Ankle Society score. After a mean follow-up of 31.7 months, all flaps survived uneventfully, except for marginal necrosis in 1 patient, infection in 1 patient, ulceration in 2 patients, and secondary thinning in 3 patients. The sensation of each flap was restored. A total of 87% and 90% of the patients exhibited 5 or more positive response points in the Semmes-Weinstein monofilament touch and sharp-blunt discrimination testings, respectively. The mean axial circumference of the reconstructed foot was 27.4 cm (the unaffected side was 25.8 cm). All patients achieved mobility in ordinary shoes with a mean functional score of 74.6. The thinned nerve-selective sensate ALT perforator flap can be a favorable option for foot and ankle reconstruction. This method also offers the possibility of preserving the nerve branch at the donor thigh.

Bioinspired adaptable multiplanar mechano-vibrotactile haptic system

Several gaps persist in haptic device development due to the multifaceted nature of the sense of touch. Existing gaps include challenges enhancing touch feedback fidelity, providing diverse haptic sensations, and ensuring wearability for delivering tactile stimuli to the fingertips. Here, we introduce the Bioinspired Adaptable Multiplanar Haptic system, offering mechanotactile/steady and vibrotactile pulse stimuli with adjustable intensity (up to 298.1 mN) and frequencies (up to 130 Hz). This system can deliver simultaneous stimuli across multiple fingertip areas. The paper includes a full characterisation of our system. As the device can play an important role in further understanding human touch, we performed human stimuli sensitivity and differentiation experiments to evaluate the capability of delivering mechano-vibrotactile, variable intensity, simultaneous, multiplanar and operator agnostic stimuli. Our system promises to accelerate the development of touch perception devices, providing painless, operator-independent data crucial for researching and diagnosing touch-related disorders.

Neuropsychiatric considerations in treating anorexia nervosa patients with osteopathic manipulative medicine: a narrative review.

Osteopathic manipulative medicine (OMM) has a growing recognition in serving as an effective treatment topromote adaptation and homeostasis of the body by addressing musculoskeletal, neural, vascular, and lymphatic structures to promote self-healing and regulation. OMM can treat the musculoskeletal tension and sympathetic hyperactivity resulting from the increased cortisol response and hypersensitivity found in varying psychiatric illnesses, including anorexia nervosa (AN). This paper addresses the considerations necessary for treating AN patients with OMM, emphasizing the need to evaluate their abnormal high-level neuronal processing of sensory information, including differences in touch perception compared to the general population. Current literature was gathered utilizing a combination of the following keywords: anorexia nervosa, perception of touch, and osteopathic manipulative medicine/treatment. No literature was found addressing the effects of OMM on treating AN patients. Eight studies addressed the change in perception of touch found in AN patients. Results of the literature review reveal that the perceptions of touch in AN patients are distorted and can lead to reduced perceived pleasantness encountered in social interactions and touch. Specific changes have been found in C-tactile (CT) afferents responsible for the positive effects of touch, thus influencing emotional regulation. The significance of addressing this topic is to provide insight into the pathophysiological processes of AN and to inform physicians of unconventional stimuli that may exacerbate AN symptoms and behaviors. Further study is required to elucidate the role and mechanism of OMM in patients with AN and whether manual therapy could worsen pathological behavior and thinking patterns seen in AN patients. Such studies could include, but are not limited to, examining biological factors such as cortisol levels in AN patients receiving OMM and collecting data about AN patients' thinking patterns and behavior during OMM treatment.

Relations between tactile sensitivity of the finger, arm, and cheek skin over the lifespan showing decline only on the finger.

Touch sensitivity generally declines with age, contributing to loss of manual dexterity and tactile function. We investigated how touch changes over the lifespan, using different tests and on three body sites. We used a classical test of force detection sensitivity, where calibrated monofilaments were applied passively to the right index finger pad, forearm, and cheek. In addition, at the index, we used an active touch spatial discrimination task, developed by our group. Spatial discrimination was estimated through participants' ability to evaluate the distance between parallel bands printed on acrylic plates. Data were collected from 96 healthy women, aged 20-75 years. Force detection and tactile spatial discrimination on the index deteriorated significantly with age; however, no change was found for tactile detection on the forearm or cheek. Tactile detection on the cheek remained remarkably highly sensitive throughout life. There was a significant positive relationship between force detection and spatial discrimination on the index. Further, force detection on the forearm was significantly associated with detection on the index and cheek. Our results suggest a decrease in touch perception with age on the index finger pad, yet a preservation of tactile sensitivity in hairy skin. This opens discussion about the impact of daily activities upon the glabrous hand skin and on the function of hairs in tactile sensitivity. We highlight the need for new methods in evaluating tactile sensitivity on hairy skin.

Thermal Effusivity Assessment of Sportswear Fabrics in the Dry State: Stacked and Air-Hoop Methods

Abstract In recent years, thermal effusivity, a property that describes the warm or cool touch perception, has gained significant attention in the apparel industry as it contributes to human thermophysiological comfort. The current study aims to explore the thermal effusivity of 27 sportswear fabrics, including woven and knitted structures with various fiber contents, using the stacked method (according to ASTM D7984-21, Standard Test Method for Measurement of Thermal Effusivity of Fabrics Using a Modified Transient Plane Source (MTPS) Instrument) and a modified air-hoop method. The results obtained revealed that the pressure range specified in ASTM D7984-21 (10–50 kPa) may cause fabric compression, resulting in the measurement of a material-based thermal effusivity rather than the fabric thermal effusivity. A pressure of 1 kPa was found to be more appropriate for obtaining accurate measurements of sportswear fabrics without altering their three-dimensional structure. Furthermore, a strong correlation was observed between the stacked and air-hoop methods for fabrics with thicknesses close to or greater than 0.4 mm. The air-hoop method simulates the configuration when the fabric is worn as part of a garment. The new knowledge provided by this research will enhance the accuracy of the thermal effusivity measurement of sportswear fabrics. It will contribute to the development of more comfortable fabrics considering realistic garment use scenarios.

Improved tactile speech perception and noise robustness using audio-to-tactile sensory substitution with amplitude envelope expansion

Recent advances in haptic technology could allow haptic hearing aids, which convert audio to tactile stimulation, to become viable for supporting people with hearing loss. A tactile vocoder strategy for audio-to-tactile conversion, which exploits these advances, has recently shown significant promise. In this strategy, the amplitude envelope is extracted from several audio frequency bands and used to modulate the amplitude of a set of vibro-tactile tones. The vocoder strategy allows good consonant discrimination, but vowel discrimination is poor and the strategy is susceptible to background noise. In the current study, we assessed whether multi-band amplitude envelope expansion can effectively enhance critical vowel features, such as formants, and improve speech extraction from noise. In 32 participants with normal touch perception, tactile-only phoneme discrimination with and without envelope expansion was assessed both in quiet and in background noise. Envelope expansion improved performance in quiet by 10.3% for vowels and by 5.9% for consonants. In noise, envelope expansion improved overall phoneme discrimination by 9.6%, with no difference in benefit between consonants and vowels. The tactile vocoder with envelope expansion can be deployed in real-time on a compact device and could substantially improve clinical outcomes for a new generation of haptic hearing aids.

Ketamine reduces the neural distinction between self- and other-produced affective touch: a randomized double-blind placebo-controlled study

A coherent sense of self is crucial for social functioning and mental health. The N-methyl-D-aspartate antagonist ketamine induces short-term dissociative experiences and has therefore been used to model an altered state of self-perception. This randomized double-blind placebo-controlled cross-over study investigated the mechanisms for ketamine’s effects on the bodily sense of self in the context of affective touch. Thirty healthy participants (15 females/15 males, age 19–39) received intravenous ketamine or placebo while performing self-touch and receiving touch by someone else during functional MRI – a previously established neural measure of tactile self-other-differentiation. Afterwards, tactile detection thresholds during self- and other-touch were assessed, as well as dissociative states, interoceptive awareness, and social touch attitudes. Compared to placebo, ketamine administration elicited dissociation and reduced neural activity associated with self-other-differentiation in the right temporoparietal cortex, which was most pronounced during other-touch. This reduction correlated with ketamine-induced reductions in interoceptive awareness. The temporoparietal cortex showed higher connectivity to somatosensory cortex and insula during other- compared to self-touch. This difference was augmented by ketamine, and correlated with dissociation strength for somatosensory cortex. These results demonstrate that disrupting the self-experience through ketamine administration affects neural activity associated with self-other-differentiation in a region involved in touch perception and social cognition, especially with regard to social touch by someone else. This process may be driven by ketamine-induced effects on top-down signaling, rendering the processing of predictable self-generated and unpredictable other-generated touch more similar. These findings provide further evidence for the intricate relationship of the bodily self with the tactile sense.

TMC6 functions as a GPCR-like receptor to sense noxious heat via Gαq signaling

Thermosensation is vital for the survival, propagation, and adaption of all organisms, but its mechanism is not fully understood yet. Here, we find that TMC6, a membrane protein of unknown function, is highly expressed in dorsal root ganglion (DRG) neurons and functions as a Gαq-coupled G protein-coupled receptor (GPCR)-like receptor to sense noxious heat. TMC6-deficient mice display a substantial impairment in noxious heat sensation while maintaining normal perception of cold, warmth, touch, and mechanical pain. Further studies show that TMC6 interacts with Gαq via its intracellular C-terminal region spanning Ser780 to Pro810. Specifically disrupting such interaction using polypeptide in DRG neurons, genetically ablating Gαq, or pharmacologically blocking Gαq-coupled GPCR signaling can replicate the phenotype of TMC6 deficient mice regarding noxious heat sensation. Noxious heat stimulation triggers intracellular calcium release from the endoplasmic reticulum (ER) of TMC6- but not control vector-transfected HEK293T cell, which can be significantly inhibited by blocking PLC or IP3R. Consistently, noxious heat-induced intracellular Ca2+ release from ER and action potentials of DRG neurons largely reduced when ablating TMC6 or blocking Gαq/PLC/IP3R signaling pathway as well. In summary, our findings indicate that TMC6 can directly function as a Gαq-coupled GPCR-like receptor sensing noxious heat.

The Inter-Subjective Touch in On Body and Soul

Abstract This article examines the inter-subjective touch in Ildikó Enyedi's film On Body and Soul (2017), employing a phenomenological approach by analyzing the aspects of horror, pleasure, dreaming, and breath. This film recontextualizes horror and reaffirms pleasure through the inter-subjective touch. The binary setting between the dreaming world and the waking world, through the perception of touch, is used not to disdain the cruel reality but to arouse inter-subjectivity. The representation of breath illuminates another tactility regarding spatiality and inter-subjectivity. I argue that On Body and Soul constructs layers of tactility and inter-subjectivity between the film and the spectator; the two protagonists (Mária and Endre); human and non-human; dreaming and waking; and mind and body.

A Suspended, 3D Morphing Sensory System for Robots to Feel and Protect.

Artificial sensory systems with synergistic touch and pain perception hold substantial promise for environment interaction and human-robot communication. However, the realization of biological skin-like functional integration of sensors with sensitive touch and pain perception still remains a challenge. Here, a concept is proposed of suspended electronic skins enabling 3D deformation-mechanical contact interactions for achieving synergetic ultrasensitive touch and adjustable pain perception. The suspended sensory system can sensitively capture tiny touch stimuli as low as 0.02Pa and actively perceive pain response with reliable 5200 cycles via 3D deformation and mechanical contact mechanism, respectively. Based on the touch-pain effect, a visualized feedback demo with miniaturized sensor arrays on artificial fingers is rationally designed to give a pain perception mapping on sharp surfaces. Furthermore, the capability is shown of the suspended electronic skin serving as a safe human-robot communication interface from active and passive view through a feedback control system, demonstrating potential in bionic electronics and intelligent robotics.

Investigating the basis of lineage decisions and developmental trajectories in the dorsal spinal cord through pseudotime analyses.

Dorsal interneurons (dIs) in the spinal cord encode the perception of touch, pain, heat, itchiness and proprioception. Previous studies using genetic strategies in animal models have revealed important insights into dI development, but the molecular details of how dIs arise as distinct populations of neurons remain incomplete. We have developed a resource to investigate dI fate specification by combining a single-cell RNA-Seq atlas of mouse embryonic stem cell-derived dIs with pseudotime analyses. To validate this in silico resource as a useful tool, we used it to first identify genes that are candidates for directing the transition states that lead to distinct dI lineage trajectories, and then validated them using in situ hybridization analyses in the developing mouse spinal cord in vivo. We have also identified an endpoint of the dI5 lineage trajectory and found that dIs become more transcriptionally homogeneous during terminal differentiation. This study introduces a valuable tool for further discovery about the timing of gene expression during dI differentiation and demonstrates its utility in clarifying dI lineage relationships.

Evolutionarily conserved neural responses to affective touch in monkeys transcend consciousness and change with age

Affective touch-a slow, gentle, and pleasant form of touch-activates a different neural network than which is activated during discriminative touch in humans. Affective touch perception is enabled by specialized low-threshold mechanoreceptors in the skin with unmyelinated fibers called C tactile (CT) afferents. These CT afferents are conserved across mammalian species, including macaque monkeys. However, it is unknown whether the neural representation of affective touch is the same across species and whether affective touch's capacity to activate the hubs of the brain that compute socioaffective information requires conscious perception. Here, we used functional MRI to assess the preferential activation of neural hubs by slow (affective) vs. fast (discriminative) touch in anesthetized rhesus monkeys (Macaca mulatta). The insula, anterior cingulate cortex (ACC), amygdala, and secondary somatosensory cortex were all significantly more active during slow touch relative to fast touch, suggesting homologous activation of the interoceptive-allostatic network across primate species during affective touch. Further, we found that neural responses to affective vs. discriminative touch in the insula and ACC (the primary cortical hubs for interoceptive processing) changed significantly with age. Insula and ACC in younger animals differentiated between slow and fast touch, while activity was comparable between conditions for aged monkeys (equivalent to >70 y in humans). These results, together with prior studies establishing conserved peripheral nervous system mechanisms of affective touch transduction, suggest that neural responses to affective touch are evolutionarily conserved in monkeys, significantly impacted in old age, and do not necessitate conscious experience of touch.

Propensity to trust shapes perceptions of comforting touch between trustworthy human and robot partners

Touching a friend to comfort or be comforted is a common prosocial behaviour, firmly based in mutual trust. Emphasising the interactive nature of trust and touch, we suggest that vulnerability, reciprocity and individual differences shape trust and perceptions of touch. We further investigate whether these elements also apply to companion robots. Participants (n = 152) were exposed to four comics depicting human–human or human–robot exchanges. Across conditions, one character was sad, the other initiated touch to comfort them, and the touchee reciprocated the touch. Participants first rated trustworthiness of a certain character (human or robot in a vulnerable or comforting role), then evaluated the two touch phases (initiation and reciprocity) in terms of interaction realism, touch appropriateness and pleasantness, affective state (valence and arousal) attributed to the characters. Results support an interactive account of trust and touch, with humans being equally trustworthy when comforting or showing vulnerability, and reciprocity of touch buffering sadness. Although these phenomena seem unique to humans, propensity to trust technology reduces the gap between how humans and robots are perceived. Two distinct trust systems emerge: one for human interactions and another for social technologies, both necessitating trust as a fundamental prerequisite for meaningful physical contact.

Examining Illusory Touch Perception in Virtual Reality among Virtual Reality Users

The phenomenon of illusory touch perception in virtual reality (VR) is a subject of increasing intrigue within online VR communities, where users report experiencing tactile sensations in the absence of direct physical contact, triggered solely by visual stimuli. This paper presents an exploratory study aimed at understanding the underlying mechanisms that contribute to the development of such illusory touch perceptions in immersive virtual environments. Through an online survey targeting VR users, this study collected qualitative data on the nature and frequency of these experiences. The survey was complemented by a review of existing literature on touch perception and multisensory integration, providing a foundational understanding of how sensory information is processed and perceived. The findings suggest that certain visual cues in VR can evoke tactile sensations, a phenomenon that may be enhanced by the immersive quality of the virtual environment and the user's previous sensory experiences and expectations. This paper discusses potential contributors to the phenomenon, such as the realism of the virtual environment, the user's level of immersion and presence, and the congruence of multisensory stimuli. Although this study sheds light on the conditions that may facilitate illusory touch perception in VR, the complexity of human sensory processing necessitates further research. Controlled experimental studies are required to establish a causal relationship between specific factors and the experience of illusory touch in VR, which could have significant implications for the fields of virtual reality and sensory augmentation technology.