The Influence of Emotional Closeness on Interindividual Touching

Interpersonal tactile stroking stimulation activates different peripheral nerve fibers, especially C-tactile afferents, which encode pleasant and erotic sensations. Hence, humans typically stroke close interaction partners with velocities that are suited to stimulate C-tactile afferents in the touch receivers’ skin. We aim to replicate this finding and we furthermore hypothesized that humans adjust their stroking velocity depending on the relationship with the interaction partner. We tested 60 participants in total (29 men, 31 women, mean age 23.3 years ± 3.6 years SD). They were asked to stroke their partner, their friend, a female stranger, a male stranger, an artificial arm and a table. Stroking was recorded by a video camera and each participant rated the emotional closeness to and attractiveness of each human interaction partner. In addition, we determined the velocity that each participant preferred to be stroked with in a forced choice paradigm. The participants stroked other humans slower and more in the optimal range for C-tactile fiber activation than non-humans. The stroking velocity was related to ratings of sympathy. The participants did not adjust their stroking velocities towards the stimulation they preferred for themselves. In conclusion, our study reaffirms that interindividual stroking touch is targeted to activate C-tactile fibers in the touch receiver. Furthermore, humans adjust their stroking velocity according to sympathy and interindividual attraction.