A psychophysical characterization of tactile and temperature perception on the human torso

Numerous studies have been conducted to investigate touch on the hand and forearm, but less is known about the rest of the body, particularly the torso and breasts, which play an important role in affective touch. We conducted psychophysical tests on three skin sites on the torso: upper breast, nipple-areola complex (NAC), and under the breast, as well as on two control sites: palm and forearm. We studied touch pleasantness and intensity by applying gentle caress-like strokes using a soft brush, and measured temperature and tactile detection thresholds. The results show an inverted U-shaped relationship for pleasantness over increasing stroking velocity for all skin sites, although we found some differences between sites, particularly at 30 cm.s ^-1 , where participants found stroking on the NAC to be more intense and women additionally found it to be less pleasant. For temperature detection, we found that the NAC was more sensitive in men. For tactile detection, we mainly observed that the areola was far less sensitive than the other areas. Together, these results provide insights into tactile perception in the torso on a fundamental level, which can be applied to understanding how to regain sensations after mastectomy.