Gravity and perceptual stability during translational head movement on earth and in microgravity

Perceptual scaling of visual and inertial cues: effects of field of view, image size, depth cues, and degree of freedom

In the field of motion-based simulation, it was found that a visual amplitude equal to the inertial amplitude does not always provide the best perceived match between visual and inertial motion. This result is thought to be caused by the "quality" of the motion cues delivered by the simulator motion and visual systems. This paper studies how different visual characteristics, like field of view (FoV) and size and depth cues, influence the scaling between visual and inertial motion in a simulation environment. Subjects were exposed to simulator visuals with different fields of view and different visual scenes and were asked to vary the visual amplitude until it matched the perceived inertial amplitude. This was done for motion profiles in surge, sway, and yaw. Results showed that the subjective visual amplitude was significantly affected by the FoV, visual scene, and degree-of-freedom. When the FoV and visual scene were closer to what one expects in the real world, the scaling between the visual and inertial cues was closer to one. For yaw motion, the subjective visual amplitudes were approximately the same as the real inertial amplitudes, whereas for sway and especially surge, the subjective visual amplitudes were higher than the inertial amplitudes. This study demonstrated that visual characteristics affect the scaling between visual and inertial motion which leads to the hypothesis that this scaling may be a good metric to quantify the effect of different visual properties in motion-based simulation.

Optic flow processing for the assessment of object movement during ego movement

The vast majority of research on optic flow (retinal motion arising because of observer movement) has focused on its use in heading recovery and guidance of locomotion. Here we demonstrate that optic flow processing has an important role in the detection and estimation of scene-relative object movement during self movement. To do this, the brain identifies and globally discounts (i.e., subtracts) optic flow patterns across the visual scene-a process called flow parsing. Remaining motion can then be attributed to other objects in the scene. In two experiments, stationary observers viewed radial expansion flow fields and a moving probe at various onscreen locations. Consistent with global discounting, perceived probe motion had a significant component toward the center of the display and the magnitude of this component increased with probe eccentricity. The contribution of local motion processing to this effect was small compared to that of global processing (experiment 1). Furthermore, global discounting was clearly implicated because these effects persisted even when all the flow in the hemifield containing the probe was removed (experiment 2). Global processing of optic flow information is shown to play a fundamental role in the recovery of object movement during ego movement.