Influences of expectation, control, and predictability on vection-induced nausea and motion sickness

Substantial differences in susceptibility to nausea and motion sickness exist both between individuals provided with the same stimulation, and within individuals from one occasion to the next. The current available theories of differential susceptibility are based primarily on sensory or physiological factors, and are relatively unsuccessful in predicting the development of nausea and motion sickness symptoms. The present study represented an exploration of psychological influences on the development of nausea provoked by a rotating drum, and a continued effort to assess relationships between sensory and physiological variables and the severity of motion sickness symptoms. In the placebo-induced expectation experiment, participants who were led to believe the inert pills they ingested before exposure to the rotating drum would enhance the development of nausea actually developed less severe symptoms. Participants who were told the pills would protect them from the development of nausea and motion sickness fared no better than participants told the pills contained no active ingredient. In the perceived control and predictability experiment, participants with the ability to start and stop the rotation of the drum at their discretion experienced significantly less severe symptoms than those who could only discontinue the experiment by making a request to the experimenter. Also, providing participants with predictive information about the duration of their exposure to the rotating drum at regular intervals was effective for significantly reducing the development of nausea and motion sickness symptoms relative to participants left without such information. In an investigation of the autonomic and electrogastrographic correlates of nausea and motion sickness, it was determined that the subjective experience of nausea is accompanied by genuine physiological events. The extent to which skin conductance increased during exposure to the rotating drum, and the amount of gastric tachyarrhythmia exhibited during drum rotation were the two most predictive physiological correlates of the severity of nausea and motion sickness symptoms. Continued efforts to distinguish psychological factors that influence the subjective experience of nausea and its physiological underpinnings will improve the understanding of differential susceptibility to nausea and motion sickness, and raise the potential for more effective prevention and intervention strategies to be developed.