The individual preferred velocity of stroking touch as a stable measurement.

Affective touch is of fundamental importance in human social interactions and there is an increasing interest in using touch as a probe for general affective perception. To this end, we developed a test of preferred velocity (ToP-V) of touch and tested whether the individually preferred stroking velocity is a stable and valid measurement. In study one, thirty healthy participants (18-30years, 17 women) were examined with the ToP-V. Therefore, pairs of different slow stroking stimuli were presented by the Rotary Tactile Stimulator - a robotic device - on the forearm and the participants chose the velocity they preferred in a forced choice paradigm. A retest was conducted after about 12days. In study two, twenty-two healthy participants (20-43years, 11 women) were tested with a shorter version of the ToP-V on the forearm and also on the palm. Moreover, they rated the pleasantness and the intensity of the stroking stimulations on both body sites. Results suggest that humans possess an individual and stable preferred velocity of stroking touch (test-retest reliability r=0.86) which can be tested in a standardized procedure. A shortened 5min version of the ToP-V also exhibited reasonable test characteristics (split half reliability: r=0.7; test-retest reliability r=0.77). The ToP-V correlated well with the pleasantness ratings when tested on the forearm (r=0.65), but not when tested on the palm (r=-0.22), indicating that the ToP-V targets a C-tactile nerve fiber specific perception. Hence, the ToP-V can be used for reliably probing affective touch perception.