ELIMINATION OE REDUCTION OF MOTION SICKNESS 



381 



Screening Procedures 



Various screening procedures have been 

 suggested for detecting men highly suscep- 

 tible to motion sickness: (1) mechanical de- 

 vices which attempt to determine the 

 resistance of the individual to motion sick- 

 ness, e.g., swings, vertical accelerators, and 

 complex roll-rockers, (2) interview tech- 

 niques employing professional psychiatric 

 and psychological personnel, (3) motion sick- 

 ness questionnaires that are answered by 

 each man, e.g., during personnel processing 

 upon entrance to military service, (4) obser- 

 vation during exposure to the actual situa- 

 tion involving motion as aboard a ship or 

 airplane, (5) labyrinthine tests, and (6) 

 rmetic drugs. 



The success of these procedures depends 

 upon the degree of correlation between the 

 various forms of motion sickness. If only 

 a single factor were involved in motion sick- 

 ness, i.e., periodic acceleration, and individ- 

 uals had relatively stable thresholds for the 

 tolerance of such acceleration, it would be 

 a simple matter to predict how many, and 

 also which, individuals would be sick in the 

 presence of known accelerations. If the 

 reasonable assumption is made that there is 

 a high correlation among the various forms 

 of motion sickness, there are still several 

 factors which mask the "true relation": (1) 

 the amount of experience with different 

 forms of transportation varies markedly, (2) 

 ships, airplanes, and land vehicles vary in 

 size and speed, (3) weather conditions at the 

 time of exposure may vary, and (4) the 

 possible inability to determine reliably an 

 individual's threshold to motion siclcness in 

 a single controlled session. 



Mechanical Devices 



Swings have been used most frequently 

 to determine motion sickness susceptibility. 

 The general procedure is to swing an individ- 

 ual for 20 minutes to half an hour (less, if he 

 vomits), and to grade the response of the 

 man according to the number of symptoms 

 he displays and perhaps the time at which 



the symptoms appear. Shortcomings of the 

 swing and other devices have rested upon 

 the inability to describe adequately the re- 

 lation of the stimulus time-intensity to in- 

 cidence. 



Studies of the vahdity of swings to 

 evaluate susceptibility to motion siclmess 

 have been made using as criteria: (1) sub- 

 sequent reaction to sea- or airsickness, (2) 

 comparison of the responses of men dis- 

 qualified for duty because of motion siclmess 

 with those of men demonstrated to be re- 

 sistant, and (3) correlation of questionnaire 

 histories of motion sickness with responses 

 to the swing. 



In his summary of the literature, Mc- 

 Intyre states, "The balance of evidence at 

 present available indicates that proper use 

 of the swing test as a screen should enable 

 a substantial reduction to be made in the 

 incidence of primary airsickness ..." (79). 

 He pointed out, however, that failure to 

 control the test properly, such as failure 

 to fix head position during the swing test, 

 may produce spurious results. Hemingway 

 (47) points out that it is necessary to repeat 

 swing tests on all individuals who are sick 

 on the first occasion. In this manner, the 

 men showing no adaptation to motion sick- 

 ness might be separated from the men who 

 are somewhat susceptible but who would 

 adapt if given sufficient exposures. 



According to Table III, taken from 

 Hemingway's data (47), if all men who re- 

 acted to the swing had been eliminated, 

 about 27 percent, or 116, of the total group 

 would have been screened. Of these, 62 

 men had a history of motion siclmess and 

 54 did not. The efficiency of this screening 

 can be estimated from the fact that of the 

 33 percent of the men with positive histories 

 of motion sickness, one half could have been 

 eliminated on the swing test but at the 

 expense of one "good" man for every sus- 

 ceptible man. 



A relation between history of motion sick- 

 ness and symptoms induced by a "Roll 

 Rocker" machine was reported by Morton 



