Psychophysical investigation on tactual material perception

Abstract

Affective touch takes up a prominent role in regulating one’s general sense of wellbeing. Previous studies examining touch indicated the role of interpersonal touch in human’s and animal’s emotional development, alleviating pain, and emotional bonds. This raises the possibility that humans may have adapted to prefer contact with human’s body and skin. However, the relationship between affective sensation and physical parameters is not well understood. Thus, it is critical to investigate the physical parameters that elicit the effect of affective touch. Drawing on three major perceptual dimensions of physical properties - ‘roughness/smoothness’, ‘softness/hardness’, and ‘coldness/warmness’, the present study investigated the effect of temperature and softness on pleasant sensation evoked by touch. Participants actively touched three sets of polyurethane rubbers from hot, room and cold condition, and estimated either the perceived magnitude of pleasantness (pleasantness group), or softness (softness group). The results revealed that the magnitude estimates of pleasantness and softness increased monotonically as a function of compliance (a major physical determinant of softness). In the pleasantness group, magnitude estimates of pleasantness were highly similar at all three temperature conditions. By contrast, the magnitude estimates as a function of compliance of cold stimuli was greater than other temperature stimuli in the softness group. These results suggest that temperature affects magnitude estimates of softness but not for pleasantness. The present study speculated that area of contact between fingers and stimuli was more salient in the cold condition as compared to other temperature conditions, thus leading to more accurate estimates of compliance.