Impact of Physical and Visual Motion on the Subjective Perception of Vertical Orientation

Abstract This paper investigates human pitch motion perception under varying visual and mechanical motion conditions and evaluates the predictive performance of the Subjective Vertical Conflict (SVC) model. Thirty-two participants experienced controlled ramp-like pitch rotation stimuli at four mean rotational rates (0.5, 1, 2.5, and 5 degrees per second) across four visual conditions (Only Vision, External Vision, Internal Vision, and No Vision) and were asked to continuously indicate their perceived rotation with respect to gravity. Results showed that participants consistently underestimated pitch rotation amplitude by around 20% and exhibited an average response delay of 0.75 seconds, while showing no significant effects of vision when comparing across the three conditions involving mechanical pitch motion.With published parameter values, the SVC model generated highly unrealistic pitch perception predictions.The SVC-VR model (omitting a visual verticality input) even predicted an incorrect perceived motion direction in the Only Vision condition. Retuning the SVC-VR model's parameters was found to significantly improve its fit to the measured subjective data, and incorporating vestibular perception thresholds in the model further enhanced accuracy.These results reveal the complexity of sensory integration in motion perception and demonstrate crucial limitations of current models and published parameter values.Future research should validate model adaptations across more diverse motion paradigms for motion perception and motion sickness to enhance prediction accuracy in virtual reality, automated vehicles, and simulator environments.