Perceptual scaling of whole-body low frequency linear oscillatory motion

Evidence that Z-axis oscillation in the Earth-vertical plane is more provocative of motion sickness than the equivalent imposed oscillation acting in the Earth-horizontal raises the possibility that horizontal oscillation is perceived as less intense than equivalent vertical oscillation. In Experiment 1, subjects (n = 8) were oscillated through their head Z-axis in both the Earth-vertical and horizontal planes. In Experiment 2, another group (n = 10) were oscillated through their head Y-axis in the Earth-horizontal. Stimuli were 5 cycles of motion at 0.3 Hz ranging in 3.5 dB intervals from 0.19 to 2.15 m.s-2 (Expt. 1) and from 0.1 to 3.98 m.s-2 (Expt. 2). Perceptual scaling of intensity against acceleration was similar irrespective of direction of oscillation in the Earth-plane or head-body axis. Displacement tended to be overestimated, this being most marked for the lower acceleration levels in the horizontal condition. Results supported the notion that Stevens' Power Law exponents decrease as a function of increasing stimulus range. Differences in perception of oscillation intensity and displacement do not seem to explain the markedly greater nauseogenic potential of vertical oscillation.