The Impact of Off-Axis Visual Rotations on Pitch Vection

Vection, illusory translation and/or rotation sensations, has been studied extensively in the context of virtual environments. Past work focusing on illusory rotation sensations has focused almost exclusively on rotations aligned with the cardinal rotational axes of the head (i.e., on-axis rotations), which is problematic because it does not fully translate to the real world and virtual environments as rotations are often not aligned with the cardinal rotational axes of the head (i.e., off-axis rotations). While there is limited work examining perceptual experiences of vection elicited by off-axis visual rotations, there is work suggesting that it may elicit visuo-vestibular conflicts and motion sickness, implying that it should result in a less compelling experience of vection. To test this possibility, we had 40 participants complete an experiment in which they were exposed to visual scenes that featured different roll-tilts (-45°, 0°, and +45° relative to the rotational axes of their head) and visual motions (pitch rotation or no pitch rotation). It was found that when participants were exposed to visual pitch rotations when there was no visual roll-tilt it resulted in vection which started sooner, lasted longer, and was more convincing than when the scene was roll-tilted 45° to the right or left. Furthermore, all three of the aforementioned conditions elicited vection more than the no visual pitch rotation conditions. This suggests that off-axis visual rotations can diminish but not abolish the occurrence of vection. Additional work is needed to better understand the constraints of this effect.