Failure to update spatial location correctly using visual cues alone

Abstract

 

As we move through the world we update the perceived position of objects such that they appear to remain stationary and so that we continue to know where they are relative to ourselves. Self-motion information that could potentially be used to do this arises both from the retina and from extra-retinal sources such as the vestibular and somatosensory systems, and efferent copy of motor commands. Here we assess whether visual information alone is sufficient to accurately update our view of space. Observers sat in the Immersive Virtual environment at York (IVY) formed by six rear projection screens that fully enclose the viewer. On each screen to appropriate view of an 8′ cubic room was presented stereographically (using shutter goggles) with the correct perspective for the viewer. The virtual room was shifted sinusoidally ±10cms up/down, left/right or towards/away from the stationary observer at 0.5 Hz. A virtual playing card was presented floating in front of the observer at one of six distances. The card's movement was locked in phase and direction with the room's movement. The amount of the card's displacement was varied in a response to whether observers judged it to be moving further or less far than the virtual room. Its movement was varied by a double staircase routine that gravitated towards the point where the movement of the card and virtual room were judged to be identical. Statistically indistinguishable results were found for up/down, left/right and towards/away motions of the room. In all cases subjects arranged the card's movement not so as to match the actual displacement of the room but instead to maintain its visual direction relative to the visual scene: perspective alignment was maintained at the expense of spatial position. In the absence of the non-retinal information about self-motion, observers cannot accurately update their change in viewpoint relative to the environment or the position of an object within it.

 

Footnotes

 Supported by NASA Cooperative Agreement NCC9-58 with the National Space Biomedical Research Institute, the Canadian Space Agency, the Centre for Research in Earth and Space Technology (CRESTech) and the Natural Sciences and Engineering Research Council of