Ryo Kitada

Autonomous sensory meridian response (ASMR) is a tingling sensation at the scalp and moving down the neck, which is often accompanied by positive feelings. ASMR is typically induced by auditory stimulation produced by someone’s actions, but studies suggest that such auditory-evoked ASMR can be modulated by visual input. What factors contribute to audiovisual interactions that generate ASMR? Although studies have shown that audiovisual congruency plays a role, the contributions of other visual factors, such as perspective and proximity, remain poorly understood. Here, we conducted two preregistered psychophysical experiments to examine the effects of visual perspective and audiovisual congruency on ASMR. Participants rated the intensity, valence, and arousal of experienced ASMR after watching video clips in which audiovisual temporal synchrony was manipulated. In Experiment 1, participants observed a dummy head being stimulated with objects by another person (third-person perspective), and audiovisual congruency showed no significant effects across perceptual dimensions. In Experiment 2, where both audiovisual congruency and visual perspective were manipulated, the congruency effect of the intensity emerged only when participants observed the actions from a first-person perspective. These results highlight the critical role of visual perspective in visuo-auditory interactions underlying ASMR evoked by others’ action sounds.

Affective touch has attracted significant interest due to its positive effects on child development and adult well-being. Studies showed that light and slow stroke of soft brush on hairy skin elicits affective sensation by activating C-Tactile fibers. Mid-air haptics, which uses focused ultrasound to create tactile sensations in free space, offers a promising method for eliciting affective changes. However, it remains poorly understood to what extent mid-air haptics can produce the perception similar to a brush stroke on hairy skin. Here, we conducted a psychophysical study comparing the tactile perception of mid-air ultrasound stimulation with that of real materials (sandpaper, aluminum resin, urethane rubber, cloth, and soft brush). Participants rated each stimulation on the dorsum of hand along three affective touch dimensions (pleasantness, surprise, ticklishness) and three discriminative touch dimensions (smoothness, softness, warmness). Univariate analyses revealed that ultrasound stimuli differed from aluminum resin, sandpaper, and urethane rubber in one or more dimensions of discriminative touch. Ultrasound stimulation with 10 Hz amplitude modulation significantly felt more pleasant than sandpaper, while no consistent differences between ultrasound and real textures ratings was observed in surprise and ticklishness. Multivariate analyses showed that ultrasound stimuli with amplitude modulation at 10 Hz and 100 Hz were significantly closer to real textures than unmodulated ultrasound. Questionnaires showed that over half of the participants identified ultrasound stimulation as a brush or cotton. These findings suggest that mid-air haptics can evoke perceptual attributes overlapping with those of real textures, including soft brushes, on hairy skin. Moreover, amplitude modulation may enhance the perceptual resemblance to realistic textures.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder defined by social communication deficits, repetitive behaviors and restricted interests. Studies have reported aberrant sensory responses, including altered experiences of social touch, in individuals with ASD. However, the relationship between atypical social touch and social networks in ASD remains poorly understood. Social touch is used to strengthen and manage social networks in many species. Studies in general populations across diverse cultures show that the extent of permissible touch is consistently linked to the strength of emotional bonds between the toucher and the touched individual. This study examined relationship-specific patterns of social touch and their association with emotional bonding in individuals with ASD. Seventy adults with ASD and 70 typically developed (TD) adults rated their emotional bonds with different social network members (e.g., partners, fathers, strangers) and the pleasantness of being touched by each. Participants also identified body regions where they allowed touch. We hypothesized that patterns of interpersonal touch allowance and emotional bonding, and their relationship, would differ between ASD and TD adults. In all social network members except children and female friends, ASD adults allowed significantly less social touching than TD adults. Compared to TD adults, ASD adults also reported having significantly weaker emotional bonds with one social network member and experiencing significantly less pleasantness when touched by multiple members of their social network. In both groups, strength of emotional bond was significantly correlated with permissible touch area. Linear regression analyses showed that our ASD participants were more reliant on bodily touch allowance for emotional bonding than the TD controls. More participants are necessary to secure sufficient number of social network members in ASD. Our results suggest that adults with ASD generally prefer less social touch from most social network members and show reduced emotional bonding with only a specific connection. In addition, touch allowance was more strongly associated with emotional bonding in ASD than TD adults. These findings highlight the influence of autistic traits on the relationship between social touch and emotional bonding within social networks.

Aim: Previous studies have reported atypical sensory responses in individuals with autism spectrum disorder (ASD) and their implications for social touch. Although adults with ASD often report discomfort with being touched by others, their preferences for the physical properties of objects are less well understood. In a prior study, we observed that, in typically developed (TD) adults, compliance (a physical correlate of softness) increased tactile pleasantness for deformable surfaces up to levels comparable to those of human body parts. In the present study, we conducted psychophysical experiments to test whether individuals with ASD show atypical affective responses to soft objects resembling human body parts.Methods: Thirty‐six adults with ASD and 36 TD adults numerically estimated the perceived pleasantness or softness while lightly pressing urethane rubbers with their right index fingers.Results: The results revealed that pleasantness increased as a function of compliance, but this increase was significantly smaller for patients with ASD than TD adults, particularly at compliance levels including human body parts. However, the perceived softness increased as a function of compliance highly similarly between the ASD and TD groups.Conclusions: These findings demonstrate an atypical preference of individuals with ASD for soft objects such as human body parts, which may help explain their tendency to avoid social touch.

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. Our group has demonstrated that compliance (a physical correlate of softness) increased the tactile pleasantness of a deformable surface until it reaches around the same level as those of human body parts. However, individuals such as those with autism spectrum disorder (ASD) often avoid being touched by others. Does ASD have atypical affective response patterns to soft objects like human body parts? Herein, adults with ASD and typically developed (TD) adults numerically estimated the perceived pleasantness or softness while lightly pressing urethane rubbers with their right index fingers. The results revealed that pleasantness increased as a function of compliance, but this increase was smaller for ASD than TD, particularly at compliance levels including human body parts. However, the perceived softness increased as a function of compliance similarly between the ASD and TD groups. This result demonstrates an atypical preference of ASD individuals for soft objects, which may explain the avoidance of ASD to social touch.

The extrastriate body area (EBA) is a region in the lateral occipito-temporal cortex (LOTC), which is sensitive to perceived body parts. Neuroimaging studies suggested that EBA is related to body and tool processing, regardless of the sensory modalities. However, how essential this region is for visual tool processing and nonvisual object processing remains a matter of controversy. In this preregistered fMRI-guided repetitive transcranial magnetic stimulation (rTMS) study, we examined the causal involvement of EBA in multisensory body and tool recognition. Participants used either vision or haptics to identify 3 object categories: hands, teapots (tools), and cars (control objects). Continuous theta-burst stimulation (cTBS) was applied over left EBA, right EBA, or vertex (control site). Performance for visually perceived hands and teapots (relative to cars) was more strongly disrupted by cTBS over left EBA than over the vertex, whereas no such object-specific effect was observed in haptics. The simulation of the induced electric fields confirmed that the cTBS affected regions including EBA. These results indicate that the LOTC is functionally relevant for visual hand and tool processing, whereas the rTMS over EBA may differently affect object recognition between the 2 sensory modalities.

Neuroimaging studies have shown that the lateral occipito-temporal cortex is involved in multisensory object processing. However, how essential this region is for non-visual object processing remains a matter of controversy. In this preregistered fMRI-guided repetitive transcranial magnetic stimulation (rTMS) study, we examined the causal involvement of the extrastriate body area (EBA) in multisensory object recognition. Participants used either vision or haptics to identify three object categories: hands, teapots (tools), and cars (control objects). Continuous theta-burst stimulation (cTBS) was applied over the left EBA, right EBA, or vertex (control site). Performance for visually perceived hands and teapots (relative to cars) was more strongly disrupted by cTBS over the left EBA than over the vertex, whereas no such object-specific effect was observed in haptics. Instead, exploratory analyses showed that the effect of impaired recognition for all object categories was greater when cTBS was applied over the right EBA compared to the vertex. The simulation of the induced electric fields confirmed that the cTBS affected not only EBA but also the adjacent object-sensitive region. These results indicate that the lateral occipito-temporal cortex is functionally relevant for haptic and visual object processing, though the rTMS differently affected object recognition between the two sensory modalities.

We are adept at discriminating object properties such as softness and temperature using touch. Previous studies have investigated the nature of each object property, but the interactions between these properties are not fully understood. Tactile softness perception relies on multiple sensory cues such as the size of the contact area, indentation depth, and force exerted. In addition to these cues, the temperature of the stimulus may contribute to tactile softness perception by changing the sensitivity to changes in stimulus compliance. To test this hypothesis, we conducted two psychophysical experiments in which the subjects estimated the magnitude of perceived softness after touching deformable objects. We varied the compliance and temperature of the stimuli. The linear functions of compliance fit to the magnitude estimates under cold conditions (9–15°C) were steeper than the functions fit to the magnitude estimates under room temperature (21–25°C). These results indicate that temperature can sharpen our tactile softness perception of deformable surfaces by increasing the sensitivity to differences in compliance.

Contrary to the assumption of arbitrariness in modern linguistics, sound symbolism, which is the non-arbitrary relationship between sounds and meanings, exists. Sound symbolism, including the “Bouba–Kiki” effect, implies the universality of such relationships; individuals from different cultural and linguistic backgrounds can similarly relate sound-symbolic words to referents, although the extent of these similarities remains to be fully understood. Here, we examined if subjects from different countries could similarly infer the surface texture properties from words that sound-symbolically represent hardness in Japanese. We prepared Japanese sound-symbolic words of which novelty was manipulated by a genetic algorithm (GA). Japanese speakers in Japan and English speakers in both Singapore and the United States rated these words based on surface texture properties (hardness, warmness, and roughness), as well as familiarity. The results show that hardness-related words were rated as harder and rougher than softness-related words, regardless of novelty and countries. Multivariate analyses of the ratings classified the hardness-related words along the hardness-softness dimension at over 80% accuracy, regardless of country. Multiple regression analyses revealed that the number of speech sounds /g/ and /k/ predicted the ratings of the surface texture properties in non-Japanese countries, suggesting a systematic relationship between phonetic features of a word and perceptual quality represented by the word across culturally and linguistically diverse samples.