ELEVIINATION OR REDUCTION OF MOTION SICKNESS 



383 



him "sick" and if so, how frequently and 

 how severely (7, 15). A questionnaire his- 

 tory of motion sickness has high inherent 

 validity in that a large sample of exposure 

 to motion is surveyed. It may be more 

 useful to know whether a man has ever been 

 sick on all the forms of transportation than 

 to know his reaction to a single test on a 

 device. Questionnaires and devices are not 

 mutually exclusive, however, and the use 

 of both can be combined in an effective 

 screening procedure. 



Reliability. Questionnaires have been 

 criticized more on the basis of rehability 

 than upon their intrinsic validity and ability 

 to predict susceptibility to motion sickness. 

 Four factors may detract from the reliability 

 of a motion sickness questionnaire: (1) fail- 

 ure by the individual to record motion sick- 

 ness, e.g., because of zealousness to get into 

 service, (2) overemphasis of motion sickness, 

 e.g., by a malingerer, (3) poor memory of 

 personal experience with motion, and (4) 

 misinterpretation of symptoms, e.g., a man 

 may never associate a headache, dizziness 

 or other minor symptoms on a ship or plane 

 with motion sickness. 



While these factors may be important 

 in individual cases, studies (18) of ques- 

 tionnaire-gathered histories of motion sick- 

 ness indicate that their reliability is high 

 (r = 0.90). No significant difference was 

 found for the average response on a motion 

 sickness questionnaire when given to Navy 

 recruits along with other procedures at a 

 boot camp, (a) when they had to sign the 

 questionnaire, and (b) when they were told 

 it was for research purposes only, could not 

 affect them in any way, and no names were 

 required. 



Judgments of susceptibility to seasicloiess 

 made by individuals themselves were found 

 to correlate quite highly with judgments 

 by their shipmates, although self judgments 

 of susceptibility tended to indicate slightly 

 higher susceptibility than judgments by 

 others (18). 



Validity. The relation between a history 



of motion sickness and susceptibility to mo- 

 tion sickness on devices, e.g., swings, vertical 

 accelerator and a complex roll rocker has 

 been shown to be significant (7, 49, 85). 

 Susceptibility to seasickness, as demon- 

 strated by 150 men aboard a destroyer 

 escort, was found to be related to their his- 

 tory of previous motion sickness (20). 

 This relation was sufficiently high to reduce 

 seasickness if the men had been screened on 

 the basis of the questionnaire. About half 

 of the crew who were highly susceptible 

 to seasickness were among the highest 10 

 percent of the questionnaire scores. 



Interviews 



It has been suggested that psychiatric 

 screening would reduce the number of men 

 likely to be incapacitated by some form 

 of motion sickness (22, 64, 101). Similarly 

 it has been thought that the individual who 

 is persistently motion sick is a potential 

 psychiatric casualty. Although consider- 

 able has been written about emotional fac- 

 tors in motion sickness, there is little quanti- 

 tative evidence about the reliability and 

 validity of psychiatric or non-specific psy- 

 chological interviews in detecting men likely 

 to be very motion sick. More information 

 is needed before even tentative conclusions 

 may be drawn about the usefulness of psy- 

 chiatric interviews in screening for motion 

 sickness. 



Exposure to Motion of Actual Environment 



In many instances, the process of training 

 may afford useful information about the 

 susceptibility of the individual. Not all per- 

 sonnel are exposed to motion during their 

 training, however, since certain technical 

 skills are required before they are assigned 

 to duty aboard ship. It is not uncommon 

 to have personnel trained at shore stations 

 for many months before assigning them to 

 the fleet. While it may be desirable to 

 have a short period of sea duty before ex- 

 tensive training, this procedure is difficult 

 on a large scale. The possible usefulness 



