Exploration of factors affecting the tactile sensation of human hair

This study investigated the tactile sensation of human hair to acquire fundamental knowledge for its quantitative evaluation, analyzing tactile actions and their correlation with physical properties. Three distinct types of hair bundles with varying bleaching were assessed for their frictional properties, bending properties, and apparent thickness. Furthermore, the influential relationships among sensory terms were analyzed using the DEMATEL method. A sensory evaluation was conducted using two distinct tactile protocols (“free” and “tracing”). Tactile actions during the “free” protocol were analyzed via video recording. Results indicated the evaluation of tactile sensation in hair is hierarchical, ranging from fundamental terms such as “Thick” and “Smooth” to an overall preference like “Like.” In the sensory evaluation, trends did not differ between the two tactile protocols. The perception of "thickness" correlated more strongly with bending stiffness than with actual thickness, while “Smooth” and “Soft” were associated with surface frictional and bending properties, respectively. These findings suggest the tactile sensation of hair is primarily attributed to two physical factors: surface frictional and bending properties, indicating human perception is based not on individual fibers but on the mechanical properties of the hair bundle as an assembly.