Effects of contact method and acclimation on temperature and humidity in touch perception

Physical stimuli from contacted objects are recorded by skin receptors and are transmitted to neural signals to the cerebrum to generate touch perceptions. Despite numerous studies having been conducted on the link between the physical properties of contacted objects and psychological sensations, factors besides the stimuli themselves have seldom been investigated. The contact method and acclimation to environmental factors, such as temperature and humidity, could affect the functions of responsible receptors, which, in consequence, might affect the touch perception. This study is designed around a series of experiments involving 226 human subjects adapted to the climate environments of six East-Asia cities. The results revealed that the contact method affected the responses of smoothness sensation but not the stimuli discriminations. This agrees with the hypothesis that both the slowly adapting type I (SA1) fiber and the Pacinian afferent (PC) fiber are responsible for smoothness sensation. SA1 fibers can function through passive touch because of a superficial location in the dermis, while PC fibers, which are located deeper in the dermis, are triggered during active touching. The effect of contact method on softness sensation is not significant because the responsible receptor is the SA1 fiber. The effects of acclimation to temperature and relative humidity were also investigated. Positive relationships were found with smoothness perception and negative relationships were found with warmth perception. This suggests that acclimation to temperature and relative humidity can affect the receptor thresholds and, in consequence, affect the touch sensation.