Sensitivity to lateral force is affected by concurrent yaw rotation during curve driving

During curve driving a lateral force, coupled to the off-center yaw rotation, is acting on the driver. In simulation, however, the lateral force is often not generated using off-centric rotation, thereby uncoupling translational and rotational motion cues. This may cause misalignment of the lateral force w.r.t. the motion direction along the curve. In the present study we investigated how sensitive humans are to such misalignment. We performed a psychophysical study where participants were repeatedly moved along circular trajectories. The participants’ physical orientation with respect to the motion path was systematically varied, and the participants’ task was to indicate whether they felt facing to the inside or the outside of the curve, in a two-alternative forced choice. The experiment was performed in darkness and with a congruent visual motion stimulus. Heading JND, i.e. the smallest detectable difference in yaw orientation w.r.t. the direction of motion, was measured. The results show a considerably lower sensitivity to the misalignment of the lateral force than what is commonly found for heading sensitivity along straight paths, with better performance when congruent visual information was presented. This indicates that for simulated curve driving some misalignment of the lateral force is acceptable, without affecting perceptual realism