Motion sickness during fore-and-aft oscillation: effect of the visual scene.

BACKGROUND

Repetitive braking and acceleration can cause carsickness, with the extent of sickness depending on the forward view outside the car.

HYPOTHESIS

It was hypothesized that the visual scene would influence motion sickness caused by low-frequency, low-magnitude fore-and-aft oscillation in the laboratory.

METHOD

There were 120 seated male subjects who were exposed to 30 min of 0.1-Hz fore-and-aft oscillation at an acceleration magnitude of 0.89 m x s(-2) rms (a displacement of +/- 3.18 m). Subjects sat in a cabin with one of six scenes: 1) an internal view of two-dimensional black shapes on a white background; 2) an external view of the same two-dimensional shapes; 3) an external view of six horizontal black lines; 4) a 'real' three-dimensional external view; 5) no view (blindfolded); or 6) an internal collimated view of the two-dimensional shapes. Due to practical constraints, only conditions 1, 2, and 6 were tested in a balanced order. Ratings of motion sickness were obtained at 1-min intervals.

RESULTS

Each of the six conditions caused motion sickness, with mean illness ratings that increased similarly over time regardless of viewing condition. The symptoms did not differ significantly between conditions and there was no difference in the risk of reaching an illness rating of 2, 'mild symptoms,' between the six viewing conditions.

DISCUSSION AND CONCLUSIONS

With a larger number of subjects, a small mean effect of vision might be found with motions having similar frequencies or similar magnitudes to the conditions investigated here. Nevertheless, compared with the large effects of vision with some motions, it is concluded that the visual scene has little effect on sickness caused by pure fore-and-aft oscillation at a frequency of 0.1 Hz and an acceleration magnitude of 0.89 m x s(-2) rms.