Institute of Population Health, Department of Psychological Sciences, University of Liverpool, Liverpool, United Kingdom.
Research Centre for Brain & Behaviour, School of Psychology, Liverpool John Moores University, Liverpool, United Kingdom.
PLoS One. 2023 May 23;18(5):e0281253. doi: 10.1371/journal.pone.0281253. eCollection 2023.
Low-threshold mechanosensory C-fibres, C-tactile afferents (CTs), respond optimally to sensations associated with a human caress. Additionally, CT-stimulation activates brain regions associated with processing affective states. This evidence has led to the social touch hypothesis, that CTs have a key role in encoding the affective properties of social touch. Thus, to date, the affective touch literature has focussed on gentle stroking touch. However, social touch interactions involve many touch types, including static, higher force touch such as hugging and holding. This study aimed to broaden our understanding of the social touch hypothesis by investigating relative preference for static vs dynamic touch and the influence of force on these preferences. Additionally, as recent literature has highlighted individual differences in CT-touch sensitivity, this study investigated the influence of affective touch experiences and attitudes, autistic traits, depressive symptomology and perceived stress on CT-touch sensitivity. Directly experienced, robotic touch responses were obtained through a lab-based study and vicarious touch responses through an online study where participants rated affective touch videos. Individual differences were determined by self-report questionnaire measures. In general, static touch was preferred over CT-non-optimal stroking touch, however, consistent with previous reports, CT-optimal stroking (velocity 1-10 cm/s) was rated most pleasant. However, static and CT-optimal vicarious touch were rated comparably for dorsal hand touch. For all velocities, 0.4N was preferred over 0.05N and 1.5N robotic touch. Participant dynamic touch quadratic terms were calculated for robotic and vicarious touch as a proxy CT-sensitivity measure. Attitudes to intimate touch significantly predict robotic and vicarious quadratic terms, as well as vicarious static dorsal hand touch ratings. Perceived stress negatively predicted robotic static touch ratings. This study has identified individual difference predictors of CT-touch sensitivity. Additionally, it has highlighted the context dependence of affective touch responses and the need to consider static, as well as dynamic affective touch.
低阈值机械感觉 C 纤维，即 C 触觉传入纤维（CT），对与人类抚摸相关的感觉反应最佳。此外，CT 刺激激活与处理情感状态相关的大脑区域。这一证据导致了社交触摸假说，即 CT 在编码社交触摸的情感属性方面起着关键作用。因此，迄今为止，情感触摸文献主要集中在轻柔的抚摸触摸上。然而，社交触摸互动涉及许多触摸类型，包括静态、更高力度的触摸，如拥抱和握持。本研究旨在通过研究静态与动态触摸的相对偏好以及力对这些偏好的影响，拓宽对社交触摸假说的理解。此外，由于最近的文献强调了 CT 触摸敏感性的个体差异，本研究还调查了情感触摸体验和态度、自闭症特征、抑郁症状和感知压力对 CT 触摸敏感性的影响。直接体验的机器人触摸反应是通过基于实验室的研究获得的，而间接体验的机器人触摸反应是通过在线研究获得的，参与者对情感触摸视频进行了评分。个体差异通过自我报告问卷测量来确定。一般来说，静态触摸比 CT 非最优的抚摸触摸更受欢迎，然而，与之前的报告一致，CT 最优的抚摸（速度为 1-10cm/s）被评为最舒适的。然而，对于手部背面的触摸，静态和 CT 最优的间接触摸的评分相当。对于所有速度，0.4N 比 0.05N 和 1.5N 的机器人触摸更受欢迎。参与者的动态触摸二次项是为机器人和间接触摸计算的，作为 CT 敏感性的代理测量。亲密触摸的态度显著预测机器人和间接的二次项，以及间接的静态手部背面触摸的评分。感知压力负向预测机器人静态触摸的评分。本研究确定了 CT 触摸敏感性的个体差异预测因子。此外，它还强调了情感触摸反应的上下文依赖性，以及需要考虑静态和动态情感触摸。
