Deciphering human emotion communication through skin contact quantification
Subtle contact changes underlying different emotional percepts
March 18, 2022
Shan Xu, Chang Xu, Sarah McIntyre, Håkan Olausson, Gregory J. Gerling
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. However, such contact details are still not fully understood due to the difficulty in quantifying naturalistic human touch.
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).
This work shows how touchers subtly, but significantly, vary the magnitudes of their skin-to-skin contact to convey distinct social messages. Besides improving receivers’ recognition of cued messages, this subtle tuning also correlates with receivers’ perception of underlying valence and arousal. For instance, arousal increases with velocity for stroking, and depth for holding. More interestingly, valence is tied with velocity, here for the case of human-to-human touch, which matches the trend that has been widely reported and reproduced in the case of brushing stimuli.
Experimentalsetup with 3D visual tracking system
(A) Touchers and receivers are separated by an opaque curtain and without verbal communication. Instructions and questions are displayed and recorded by computers in front of participants. The depth camera (Kinect) was set in between to capture hand-arm interactions. (B) A snapshot taken by the depth camera during the experiments. The toucher was delivering a cued emotional message to the receiver’s forearm. (C) An example 3D forearm point cloud and hand mesh. On the forearm, black line segments denote a normal vector per point, and red points illustrate the contact region. Six time-series contact attributes include: (D) contact area as the overall area of the contact region on forearm, (E) indentation depth as the average indentation of all contacted hand points relative to the forearm surface, (F) absolute value of hand velocity and its three orthogonal components. The vector of spatial hand velocity is derived from the position of the middle metacarpophalangeal joint.Longitudinal velocity is along the direction from receiver’s elbow to wrist. Vertical velocity follows the vertical direction pointing up. Lateral velocity is perpendicular to the other two velocities pointing left.
Delivered bythe same gesture, contact attributes change across emotional messages
(A) Contact attributes of messages delivered by touchers (top row) and recognized by receivers (bottom row). One attribute that well distinguishes messages, i.e.,absolute velocity (cm/s) or indentation depth (cm), is displayed per gesture.(B) Importance of contact attributes derived by their contribution in classifying successfully recognized messages. Vlg: longitudinal velocity (cm/s), Vvt: vertical velocity (cm/s), Vlt: lateral velocity (cm/s), Vabs: absolute velocity (cm/s), A: contact area (cm2), Dp: indentation depth(cm), Du: duration (s).
Absolute measurements per contact attribute, message, and gesture. Points denote trial data.
Contact attributes encode valence andarousal states
(A) Valence and arousal ratings are similar between gestures per message. Blue cross marks represent valence and arousal ratings retrieved from dataset using written word stimuli. (B) Contact attributes distinctly tune arousal and valence ratings within a gesture.Absolute velocity (cm/s) and indentation depth (cm) exhibit clear trends.
Reference:
Xu, S., Xu, C., Mcintyre, S., Olausson, H., & Gerling, G. J. Subtle Contact Nuances in the Delivery of Human-to-Human Touch Distinguish Emotional Sentiment. [DOI] IEEE Transactions on Haptics. 2022
Xu, S., Xu, C., Mcintyre, S., Olausson, H., & Gerling, G. J. 3D Visual Tracking to Quantify Physical Contact Interactions in Human-to-Human Touch. [DOI] Frontiers in Physiology. 2022
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