The influence of visual reference on stance and walking on a moving surface

It is apparent that visual information is used in maintaining stable posture and ambulating throughout the stationary world. Considerable previous research has indicated that significant perturbations of posture can be induced with a shift in the entire visual scene. In motion environments, it is assumed that posture and ambulatory ability are controlled more by vestibulo-spinal reflexes, but the role of visual reference has not been extensively studied.

In the present study, the frequency of motion-induced interruptions (MIIs) under conditions which did and did not provide a stable visual reference were compared. Subjects were tested on a motion platform driven by a simulated ship-motion profile. Two independent observers recorded MIIs for standing and walking under two conditions. In one, the subjects were allowed to see the walls and ceiling of the stationary test cubicle that housed the motion platform. In the other, curtains attached to the motion platform prevented this view. Force plate recordings were also obtained during the standing tasks.

Observers reported significantly more MIIs, and force plate recordings indicated more postural instability under the condition involving curtains.

These results suggest that manipulations, such as artificial horizons, that provide stable visual representations of the static environment within which the motion occurs may provide important health and safety measures for individuals working in modern vehicular conveyances.