AN EXPERIMENTAL EVALUATION OF SENSORY CONFLICT VERSUS POSTURAL CONTROL THEORIES OF MOTION SICKNESS

Riccio and Stoffregen (1991) presented a radical alternative to the wi dely accepted sensory conflict theory of motion sickness. Essentially, they argued that motion sickness is caused not by sensory conflict, b ut by postural instability. The current experiment was designed to eva luate three aspects of the two theories. Participants were exposed to two levels of sensory conflict while being partially restrained to red uce the possibility of postural instability. The results were that (1) motion sickness was widespread although there were few signs of postu ral instability, (2) differences in motion sickness were associated wi th differences in sensory conflict rather than with differences in pos tural stability, and (3) the frequency range of movements that precede d symptoms of motion sickness was not in the 4 to 8 Hz band, contrary to the prediction of Riccio and Stoffregen. Although these results mus t be treated with caution due to the limits of the resolving power of the analysis of participants' movements, we conclude that although the postural instability explanation has more ecological validity, it is not correct in its current form and deserves further empirical investi gation.