The contribution of expectations to motion sickness symptoms and gastric activity.

OBJECTIVE The goal of this investigation was to determine in healthy adults the effect of expectation manipulations on the development of motion sickness, as indicated by abnormal gastric myoelectric activity and subjective reports of symptoms of motion sickness. METHOD Eighty participants, moderately susceptible to motion sickness, experienced one of four conditions created from a two-variable (Expectation, Drum), two-factor model (High/Low expectation for sickness; Rotating/Stable Drum). The electrogastrogram (EGG) was recorded 6 min prior to the expectation manipulation; 6 min following the expectation manipulation; 6 min before drum activation; and 16 min during drum activation. Self-report questionnaires indicating expectation for sickness (MSEx) and motion sickness symptoms (Nausea Profile [NP]) were obtained following the expectation manipulation and exposure to the drum, respectively. RESULTS No significant differences were observed among expectation groups for retrospective reports of motion sickness (NP); however, significant differences in EGG responses to drum rotation were obtained. The unexpected results of a univariate analysis of variance (ANOVA) revealed significantly greater gastric tachyarrhythmia and less normal activity, an indication of motion sickness, in the low expectation for sickness conditions. CONCLUSION These results suggest that inducing a high expectation for sickness in healthy individuals about to be exposed to provocative motion results in a protective effect from motion sickness following exposure to the stimulus, while low expectations may induce abnormal gastric activity.