Social vs. Self -Touch: Subjective Pleasantness and the Post-auricular Reflex

Abstract

Background Touch is a fundamental component of human interaction, which can play a crucial role in emotional regulation, social bonding, and well-being. The post-auricular reflex (PAR) has proven to serve as an implicit measurement of positive affect, and therefore might also be a physiological marker of the pleasantness of touch, potentially relevant for clinical research. The aim of this project is to investigate whether social touch elicits a stronger PAR and higher subjective pleasantness ratings compared to self-touch. Methods A sample of participants (n=75), take part in a 2x2x2 within subjects experimental design. The conditions are self-touch versus social touch, touch by hand or touch by make-up brush, and touch on the participants real arm or on a fake arm. Subjective pleasantness ratings are given after each touch experience and the PAR is measured during each condition. Results A linear mixed-effects model revealed that self-touch elicited significantly higher PAR amplitudes than social touch, and that social touch was rated as significantly more pleasant than self-touch. Conclusions These findings indicate that the PAR is not a straightforward measure of pleasantness of touch, as self-touch enhanced reflex responses despite being rated as less pleasant. Suggesting that motor execution or agency may modulate the PAR independently of emotional valence.