Tactile perception of nonpainful unpleasantness in relation to perceived roughness: effects of inter-element spacing and speed of relative motion of rigid 2-D raised-dot patterns at two body loci.
Rigid surfaces consisting of spatially jittered 2-D raised-dot patterns with different inter-element spacings were moved back and forth across the skin at three different speeds (10-fold range). Within each psychophysical experiment, participants numerically estimated the perceived magnitude of either unpleasantness (nonpainful) or roughness of 2-D raised-dot surfaces applied to two stationary body sites (experiment 1: fingers; experiment 2: forearm). The psychophysical functions for the two types of perceptual judgment were highly similar at both body loci; more specifically, the perceived magnitude of unpleasantness and roughness both increased monotonically as a power function of increasing inter-element spacing, with the rate of growth declining at the upper end of the continuum. These results suggest that inter-element spacing is a critical determinant of the perceived magnitude of unpleasantness (nonpainful), as well as of roughness. Each perceptual judgment also increased as a function of increasing relative speed at both body loci. However, the magnitude of this effect was significantly greater for perceived unpleasantness than for perceived roughness; conversely, the speed effect was significantly greater on the forearm than on the fingers. Several possible explanations for these findings are considered.
Division of Cerebral Integration, National Institute for Physiological Sciences, Okazaki 444-8585, Japan. kitada@nips.ac.jp
Ryo
R
Kitada
Norihiro
N
Sadato
Susan J
SJ
Lederman
D000054:Acceleration; D000293:Adolescent; D000339:Affect; D004192:Discrimination, Psychological; D005260:Female; D006801:Humans; D007600:Judgment; D008297:Male; D010812:Physical Stimulation; D011601:Psychophysics; D013028:Space Perception; D013499:Surface Properties; D014110:Touch; D055815:Young Adult