Subtle Contact Nuances in the Delivery of Human-to-Human Touch Distinguish Emotional Sentiment

Abstract

We routinely communicate distinct social and emotional sentiments through nuanced touch. For example, we might gently hold another's arm to offer a sense of calm, yet intensively hold another's arm to express excitement or anxiety. As this example indicates, distinct sentiments may be shaped by the subtlety in one's touch delivery. This work investigates how slight distinctions in skin-to-skin contact influence both the recognition of cued emotional messages (e.g., anger, sympathy) and the rating of emotional content (i.e., arousal, valence). By self-selecting preferred gestures (e.g., holding, stroking), touchers convey distinct messages by touching the receiver's forearm. Skin-to-skin contact attributes (e.g., velocity, depth, area) are optically tracked in high resolution. Contact is then examined within gesture, between messages. The results indicate touchers subtly, but significantly, vary contact attributes of a gesture to communicate distinct messages, which are recognizable by receivers. This tuning also correlates with receivers' arousal and valence. For instance, arousal increases with velocity for stroking, and depth for holding. Moreover, as shown here with human-to-human touch, valence is tied with velocity, which is the same trend as reported with brushes. The findings indicate that subtle nuance in skin-to-skin contact is important in conveying social messages and inducing emotions.

Stroking trajectory shapes velocity effects on pleasantness and other touch percepts.

“…First, it will be important to record and quantify natural human touch as it unfolds in social interactions. Noninvasive solutions relying on 3D video recordings are currently being developed (Xu et al, 2022) and could be used to link pleasantness and other ratings as well as psychophysiological and brain measures to natural variation in touch. Second, it will be important to translate natural touch recordings into a robotic application.…”

Mechanoreceptive Aβ primary afferents discriminate naturalistic social touch inputs at a functionally relevant time scale

“…Distinct from traditional experiments that control the mechanical stimulus and vary a single feature at a time, we record from single peripheral afferents in a human-to-human touch paradigm, where multiple stimulus features, e.g., normal displacement, contact area, lateral velocity, vary simultaneously [1], [5], [36], [37]. Such naturalistic social touch interactions are closely tied to our human well-being and development, and may extend into everyday tasks such as feeding, grooming [38], and caregiving [39].…”

“…It suggests that the distinct contact patterns of elementary touch gestures, e.g., tapping, stroking, and holding, can be captured to a certain extent by all afferent subtypes. Indeed, and in comparison, expressions delivered by selective use of the same gesture can be fine-tuned to convey specific social meanings by participants making subtle changes in skin-to-skin contact, e.g., velocity, indentation depth, contact area [36]. Such nuances may be less easy to capture for certain afferents.…”

“…We might assume that neural responses to fast contact velocities are related to high arousal percepts. However, other contact characteristics, e.g., force, indentation, contact area might also contribute [36]. Therefore, precise contact quantification needs to be introduced to uncover further details of how emotional contexts of physical touch delivery are encoded by peripheral afferents [37].…”

Phantom Illusion Based Vibrotactile Rendering of Affective Touch Patterns

“…As well, it is one of the body parts with the highest acceptance of touch [8]. Touch cues on the forearm have therefore been of particular interest of researchers [9], [10]. With this paper, we aimed to give insights into the development and functionality of the armband device.…”