An Experimental Evaluation of Sensory Conflict Versus Postural Control Theories of Motion Sickness

Riccio and Stoffregen (1991) presented a radical alternative to the widely accepted sensory conflict theory of motion sickness. Essentially, they argued that motion sickness is caused not by sensory conflict, but by postural instability. The current experiment was designed to evaluate three aspects of the two theories. Participants were exposed to two levels of sensory conflict while being partially restrained to reduce the possibility of postural instability. The results were that (1) motion sickness was widespread although there were few signs of postural instability, (2) difference in motion sickness were associated with differences in sensory conflict rather than with differences in postural stability, and (3) the frequency range of movements that preceded symptoms of motion sickness was not in the 4 to 8 Hz band, contrary to the prediction of Riccio and Stoffregen. Although these results must 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 investigation.