It is typically assumed that during passive motion in darkness, velocity and traveled distances are estimated by inertial signals. The forces occurring during linear acceleration can be detected by vestibular and other sensory systems. These inertial forces are in principle indistinguishable from comparable gravitational forces during tilted orientations. In this study, we used this tilt-translation ambiguity to systematically alter gravitoinertial forces and evaluated the effect on the perception of curved-linear translation.

Participants were seated in a completely dark room on the MPI Motion Simulator and used a steering wheel to control lateral motion on an arc. A target was briefly flashed in the darkness and participants were asked to move to it. A sideways tilt was applied either in the same or in the opposite direction of lateral movement to attenuate or enhance gravitoinertial forces.

Attenuating gravitoinertial forces did not affect distance estimates, whereas enhancing gravitoinertial forces resulted in a significant but small decrease in produced distances. This suggests that self-motion perception in the absence of visual information might not be as strongly influenced by gravitoinertial forces as typically assumed. It might be based more on non-directional sensory information such as noise and vibrations that accompany almost any motion.