Motion sickness: acquisition and retention of adaptation effects compared in three motion environments.

A sharp distinction should be made between symptoms of motion-sickness per se and phenomena inferred from the symptomatology, which include rates of acquisition and decay of adaptation effects. Foreknowledge of these "derived phenomena" are valuable if it can be shown that they hold true for virtually any motion environment. Recently, we have developed a sudden-stop vestibulovisual interaction test for measuring susceptibility to motion sickness (1). The test procedure involves four successive assessments that provide not only an index of susceptibility to motion sickness but also the rates of acquisition and decay of adaptation effects. The 14 subjects participating in this test had previously served as subjects in parabolic flight experiments and seven of them had also taken part in the assessment of antimotion-sickness remedies in a slow rotation room. The present report examines whether their rates of acquisition and decay of adaptation to stressful motion represent consistent general features of their responses across motion environments. From these comparisons, it appears that an individual's rates of acquiring and losing adaptation are quite consistent in very different situations. The pattern of results also suggests modifications of the sudden-stop vestibulovisual test that should increase its effectiveness as a motion-sickness screening procedure, both for orbital flight and for terrestrial conditions.