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Experiences With Research on Motion Sickness1 GEORGE RICHARD WENDT University of Rochester SUMMARY The author's studies of motion sickness, conducted since before World War II, are briefly de- scribed. They included studies of the nature of susceptibility to motion sickness, of the effects of wave character on incidence of motion sickness, of other factors related to motion sickness, including preventive drugs, and of the effects of sickness on performance. INTRODUCTION I was invited to take part in this symposium to review the research on motion sickness for which I have been personally responsible. My associates and I have done several hundred separate researches of all degrees of magnitude from relatively small to very large. Most of these were done in the period 1939 to 1956, but some span the period from 1930 to the present. Relatively few are in normal publication chan- nels, but nearly all are at least briefly described in technical reports and so-called final reports. Let me briefly account for this state of affairs. In 1939 our involvement in war was easily pre- dicted. I decided to direct my interests in the vestibule to an area of military consequence, motion sickness. Because there were then few people with either skills or interest in motion sickness, I allowed my interest and research to cover nearly the entire gamut of possible problems. This paper will have served my purpose if it leads a few of you to seek copies of my unpub- lished reports and, hopefully, to do experiments 1 In the 38 years during which I have engaged in this re- search, it has been supported by agencies and aided by individuals far too numerous to mention. Preparation of this paper is currently aided by the University of Rochester and by a contract with the Office of Naval Research. Neither sponsor should be held accountable for the views expressed. to answer the many questions I left unanswered or insufficiently proven. The reports which give access to most others are one to the National Research Council Committee on Selection and Training of Aircraft Pilots in 1944, a final report to the Office of Naval Research in 1954, and a progress report to the National Institute of Mental Health in 1956 (refs. 1 to 3). Most of our pub- lished papers are in the Journal of Psychology. After Pearl Harbor, I was deluged by requests for answers to the problems of motion sickness. I did my best to answer these needs. From the perspective of 27 years later, my efforts do not seem to have been misleading on major issues. What follows is a selection of problems empha- sizing those we did not solve and wish someone else would soon try to solve. STUDIES OF NATURE OF SUSCEPTI- BILITY TO MOTION SICKNESS Our early wartime work, 1939 to 1942, was low-budget exploratory investigation, resulting in over 200 studies of human vestibular, auto- nomic, other physical and physiological, and psychological characteristics of those susceptible or nonsusceptible to motion sickness, as indicated by their life histories. In retrospect, I can say that most data on the nature of susceptibility were negative, i.e., of no predictive value, others were positive, but not feasible to use, and one.
30 THE ROLE OF THE VESTIBULAR ORGANS IN SPACE EXPLORATION on past history of vomiting and of motion sickness, had a moderate predictive value. Studies of Vestibular Sensitivity The magnitude and duration of vestibular nystagmus are probably not predictive of motion sickness according to a number of our studies. It is possible that visual inhibition of nystagmus is less effective in susceptibles. Habituation to rotation, with the subjects being rotated in the dark, is not related to motion-sickness suscepti- bility. This may not apply to the very different problem of habituation in the Pensacola Slow Rotation Room, where full vision is standard and sickness is common. Studies of Autonomic Responses About 50 studies of many aspects of the prob- lem of autonomic responses gave negative results. Blood pressure; pulse rate and its changes; arrhythmia; cardiac response to vestibular stimu- lation; reaction to revolver shot or to apprehen- sion; tilt-table response; cold-pressor reaction; vasomotor response to hyperventilation and to breath holding; injections of Adrenalin or of acetyl-/3-methylcholine, and others, were not usefully predictive. Other Physiological and Medical Studies Motor coordination, the electroencephalogram, somatotype, and breathing rate were unrelated to susceptibility. On the other hand, suscepti- bles made health complaints and displayed symptoms much more often. Medical histories yielded no support for their complaints, nor did infirmary records. Psychological Studies A very large number of biographical data and psychological test scores were assembled on 630 men. The results are interesting but of little practical value. The susceptibles rated slightly higher on neuroticism. They took two to three times as many courses in religion, phi- losophy, art, and music, and only half as many in economics and chemistry. They were equal in athletics, but outstanding in individual sports such as track, wrestling, and boxing. They tended to avoid liquor, coffee, and tobacco. Because almost all these data have little prac- tical use, being so heavily culturally influenced, they should be used only for understanding rather than prediction. A set of predictive criteria based on our liberal-arts college popula- tion is virtually useless for a secondary school population that does not have the same choices of activities. Predictive Value of History of Vomiting We were able to account for 4 to 35 percent of the variance of motion sickness in actual prac- tice, based on various predictions. A single test on a wave machine was least predictive. A good history of motion sickness by question- naire or interview was dependable and could account for about 20 percent of the variance, while more elaborate biographical data, adapted to a particular population, could perhaps double these odds. Unfortunately, this work was done in the days of the DC-3, the landing ship-tank, and lawn swings and may be much less useful for today's hardware. Changes in our culture require a frequent reassessment of biographical data. STUDIES OF THE EFFECTS OF WAVE CHARACTER ON MOTION SICKNESS The chances are that most of you know of my papers on the effects of wave characteristics on frequency of motion sickness. These studies became possible when more research money was available after Pearl Harbor. I started with the general observation that magnitude of acceleration was not in direct re- lationship to sickness, e.g., in riding horseback, but that time between accelerations was. My first experimental proof was that wave frequency was very important. A medium-frequency wave of 16 to 22 cpm was most effective in mak- ing men sick. I then went on, in a series of seven more experiments, to show the role of other factors. I will quote from my sixth paper: In general conclusion, then, it would appear that the capacity of a wave to induce sickness depends on wave-duration, ac- celeration-level, waveform, and energy per wave. It is clear that the effect of any one of these variables depends on its context with the others. We have obtained enormous dif- ferences in the nauseating properties of waves. The H- wave for instance (16 cpm, 0.25 g) is roughly 20 times as nauseating per unit of energy as the A-wave (32 cpm, 0.65 g).
EXPERIENCES WITH RESEARCH ON MOTION SICKNESS 31 I suggest a report by C. H. Baker (ref. 4) as a review of this work. (See also J. Psychol., vols. 39 and 57.) A general conclusion from these studies is that the human, exposed to wave action, reacts as a resonating system with a maximum output of sickness at about 20 cpm, followed by a sharp cutoff at higher frequencies. It was my hope and intention to find where in the brain or re- ceptors this resonant action took place. Un- happily, in the late 1940's our electronic tech- nology failed at both the receptor end and the cerebellum. We tried in six experiments to re- cord from various elements of the vestibular sys- tem, but essentially failed in each. It is also possible that animals may not make good sub- jects. R. L. Cramer and I, in a behavioral ex- periment, exposed 126 cats to waves of different frequencies, but found them too variable to make suitable subjects. In these present days of implanted electrodes, J. W. Wolfe has worked with me and showed that the situation is much more hopeful for finding what the central nervous system is doing. I hope that he or others can supply the answers I failed to supply. I should also mention that I failed to produce acceptable sinusoidal waves with my equipment, and used only constant acceleration waves. The problem of comparing these two wave types must eventually be done by someone who has available both types of waves. I did a little work with what is now known as canal sickness, but, except for an impression that it is more uncomfortable and longer lasting than the reaction to vertical acceleration, made no contribution. OTHER SELECTED ITEMS Motion Sickness and Fear On the basis of much behavioral evidence, I used to be unalterably opposed to the idea that motion sickness is caused by fear. I have softened my line on this, now believing that motion sickness may cause anxiety. I am still strongly opposed to the idea, popular in 1940, that people susceptible to motion sickness are cowards. Relationship of Motion Sickness to Temperature and Posture Contrary to my own expectations, we have not been able in three separate studies to show that high temperature facilitates motion sickness. Nor have we been able to establish an inter- action of temperature, body or head orientation, and wave frequency, except that an uncomfort- able posture (head 90Â° back) is accompanied by more sickness. Studies of airline passengers, requested to adopt head-up and head-back pos- tures, were inconclusive. Head Movement on the Vertical Accelerator Motion pictures of head bobbing on the vertical accelerator, taken from 240 men, showed no relationship to development of motion sickness. Motion Sickness and Efficiency of Performance All our laboratory performance studies were done immediately before and after brief ex- posures to motion (20 minutes or less). A quote from a summary of all our studies of the effects of sickness on performance (ref. 5) follows: It has now been shown that speed in code substitution, level of aspiration in rifle target fire, and speed on the Mash- burn complex coordinator are slightly decreased; speed of mirror tracing, accuracy of code substitution, accuracy of rifle fire, accuracy of dart throwing, speed of obstacle running, and speed of dash showed statistically insignificant decreases. [A] greater deficit in those nauseated as compared to those who vomited was present [in seven out of nine of these tests]. All deficits were trivial. On the other hand, interviews with chronically seasick or airsick personnel often show severe weight loss and motivational problems. Laboratory Tests of Prevention of Sickness by Drugs Sea trials and air trials of motion-sickness preventives are not replicable unless one uses hundreds of subjects. By contrast, we showed, by replicating the same procedure on five groups (total of 240 men), that findings were consistent with group sizes of 24 men. Laboratory testing seems to have advantages. It is regrettable that no facility exists for continuing such work (ref. 6). Correlated Studies Not included in this account are the results of 17 years of studies of vestibular function, eye
32 THE ROLE OF THE VESTIBULAR ORGANS IN SPACE EXPLORATION movements, and very numerous experiments on the effects of drugs on social behavior and on emotions and motivations. Many of the latter are basic to any advance in use of drugs for prevention and treatment of motion sickness (ref. 7). CONCLUDING REMARKS We believe that our multivariable experiments, planned so that each experiment included a replication of several previously used variables of a total of 14 or more, are an efficient way to obtain valid data. We have done two kinds of experiments. In motion-sickness studies on the vertical accelerator, we normally used 14 variables with one subject for each possible combination of these 14. In drug studies we have used each subject one or more times on each drug variable, always using at least four variables (i.e., drug treatments) which were used in all of our previous experiments. The level of con- sistency of our results, in both motion-sickness and drug studies, has been very satisfying. In a laboratory at Trinity College, an attempt was made to replicate our drug studies exactly, and nearly identical results were obtained that showed high correlations of drug-induced changes, one as much as r = + 0.994 when com- pared to our data. REFERENCES 1. WENDT, G. R.: Motion Sickness in Aviation. Report to the National Research Council Committee on Selection and Training of Aircraft Pilots. 1944, pp. 1-41. 2. WENDT. G. R.: Studies of Motion Sickness, Vestibular Function and of Psychological and Physiological Effects of Drugs. Final report to the Office of Naval Research, 1954, pp. 1-36. 3. WENDT, (',. R.; Nowus. H.; AND NOWLIS. V.: The Effect* of I'M,, on Social and Emotional Behavior. Progress report to the National Institute of Mental Health, Mar. 1, 1956. 4. BAKER, C. H.: Motion and Human Performance: A Review of the Literature. Technical Rept. 770-1, Human Factors Research, Inc., Goleta, Calif., Aug. 1966, pp. 1-188. 5. JOHNSON, C.: AND WENDT, G. R.: Studies of Motion Sickness: XX. Effects of Sickness on Performance in Code Substitution and Mirror Drawing. J. Psychol., vol. 57, 1964, pp. 81-84. 6. JOHNSON. C.: AND WENDT. G. R.: Studies of Motion Sick- ness: XIX. The Efficiency of Laboratory Tests of the Preventive Action of Drugs. J. Psychol.. vol. 57. 1964. pp. 71-79. 7. CAMERON. J. G.; SPECHT, P. G.; AND WENDT, G. R.: Chemical Studies of Behavior: XIV. Effects of a Dramamine-Analgesic-Caffeine Combination on Moods, Emotions and Motivations. J. Psychol., vol. 67, 1967, pp. 263-270. DISCUSSION Money: Did all the subjects wear blindfolds in all your waveform studies? Wendt: Yes.
SESSION II Chairman: MARTIN P. LANSBERG National Aeromedical Center Soesterberg, Netherlands