388 



MOTION SICKNESS, I 



importance attached to cerebral anoxia re- 

 sulting from interference with blood flow in 

 motion sickness must be minimized (32) . 



Air temperature has long been thought 

 to be important in motion sickness, because 

 of the subjective effect of feeling better when 

 going into the open air topside. Aboard 

 ship this is obviously complicated by changes 

 in vision now known to be significant in 

 inhibiting motion sickness. Constant con- 

 ditions for vision exist in the standard swing 

 test; and an analysis of results of 1000 swing 

 tests during various temperatures through- 

 out the year ranging from 0°C to 40°C, 

 indicate little effect of temperature on the 

 incidence of motion sickness (42). Slightly 

 greater motion sickness was found for tem- 

 peratures of 36-40°C, but in this tempera- 

 ture range only a few tests were run, so that 

 the results are equivocal. 



The time before or after meals, or the 

 time of day one is exposed to motion ap- 

 parently has little effect upon the occurence 

 of motion siclaiess (6). Relevant to this 

 finding of the lack of importance of meals 

 is the additional negative finding that "noth- 

 ing in the roentgenologic appearance of the 

 stomach before swing testing was found to 

 correlate with whether the subject became 

 'swing-sick' or not (75)". 



Psychogenic Factors in Motion Sickness 



Probably the most confused issue is the 

 role of such factors as suggestion, fear, and 

 personality traits in the production of motion 

 sickness. Although such factors were em- 

 phasized in early reports, there is now a 

 trend away from regarding susceptibility to 

 motion sickness as a manifestation of neu- 

 rosis or similar defect. Historically, it is 

 apparent why a "functional" or psychogenic 

 point of view was popular. For one thing, 

 the stimulus (acceleration) and the sense 

 organ affected (the vestibular apparatus) 

 were vaguely understood. Also, the person 

 being made motion sick is not aware of the 

 effect of acceleration, since the vestibular 

 apparatus does not have the degree of cor- 



tical representation of other organs of spe- 

 cial sense. Furthermore, lacking a single- 

 factor explanation, the early clinicians who 

 worked on the problem were prone to accept 

 a loose and non-specific functional interpre- 

 tation which made susceptibility to motion 

 sickness, in a sense, equivalent to a form of 

 neurosis. 



From the results of research on motion 

 sickness in animals, it is clear that motion 

 sickness can occur without unusual psycho- 

 logical predisposing factors. The mere co- 

 existence of neurosis with susceptibility to 

 motion sickness need not point to a relation 

 between them since the high incidence of 

 neurotic complaints in contemporary society 

 insures the frequent association of a neurotic 

 personality and susceptibility to motion sick- 

 ness in the same individuals. 



Fear and Motion Sickness 



The principal emotional factor that has 

 been emphasized in motion siclaiess is fear. 

 In extreme fear or anxiety, symptoms re- 

 sembling those of motion sickness may be 

 seen, and it has been suggested that fear is 

 an important element, if not the critical 

 factor, in airsickness (10). It should be 

 realized, however, that the symptoms of 

 motion sickness resemble those produced by 

 a wide variety of conditions that have little 

 in common psychologically. Fear has been 

 most stressed in airsickness, although even 

 in this instance, the hypothesis must face 

 the embarrassing fact that experienced pilots 

 may become airsick if traveling as passengers 

 (119). In a study of naval personnel, it 

 was found that there was no relation between 

 fears of drowning, explosion, and fire aboard 

 ship, and susceptibility to motion sickness 

 (18). 



The only experimental investigation of the 

 role of fear in motion sickness employed an 

 electric shock given to persons as they were 

 rotated in a chair. Individuals receiving 

 anticipated electric shocks during rotation 

 had a greater incidence of motion sickness 

 than control subjects who did not receive 



