Date Published: January 30, 2019
Publisher: Public Library of Science
Author(s): Makiko Natsume, Yoshihiro Tanaka, Astrid M. L. Kappers, François Tremblay.
Previous studies have demonstrated that skin vibration is an important factor affecting the roughness perception of fine textures. For coarse textures, the determining physical factor is much less clear and there are indications that this might be participant-dependent. In this paper, we focused on roughness perception of both coarse and fine textures of different materials (glass particle surfaces and sandpapers). We investigated the relationship between subjective roughness ratings and three physical parameters (skin vibration, friction coefficient, and particle size) within a group of 30 participants. Results of the glass particle surfaces showed both spatial information (particle size) and temporal information (skin vibration) had a high correlation with subjective roughness ratings. The former correlation was slightly but significantly higher than the latter. The results also indicated different weights of temporal information and spatial information for roughness ratings among participants. Roughness ratings of a different material (sandpaper versus glass particles) could be either larger, similar or smaller, indicating differences among individuals. The best way to describe our results is that in their perceptual evaluation of roughness, different individuals weight temporal information, spatial information, and other mechanical properties differently.
When we evaluate the characteristics of an object, we attempt to obtain some tactile information by touching the object. The tactile information is based on deformations, vibrations, and temperature changes on the skin, which are elicited by the mechanical interaction between the finger and the object. As mechanical interaction with the skin depends not only on the material properties of the object but also on the individual characteristics of the skin and the contact conditions, there will be individual differences in the induced tactile sensations. Furthermore, cognitive aspects might cause differences in tactile sensation. Tanaka et al.  showed that the sensitivity to vibrotactile stimulation and the change of the sensitivity by increasing the skin vibration varied among participants. Hollins et al.  demonstrated that perceptual space comprises two dimensions: roughness/smooth and soft/hard for some participants, whereas for other participants, space comprises three dimensions: roughness/smooth, soft/hard, and sticky/slippery. Thus, tactile sensation is extremely complex and subjective. The aim of this study is to give a first insight into individual differences on tactile sensation (in particular surface roughness). Findings of the present paper could provide useful knowledge to achieve a better understanding of the relationship between physical parameters and the tactile sensation among individuals. They will not only be valuable from a fundamental point of view, but also be useful for the design of textures and the development of haptic sensors and displays.