Updating the remembered position of targets following passive lateral translation.

Spatial updating, the ability to track the egocentric position of surrounding objects during self-motion, is fundamental to navigating around the world. However, people make systematic errors when updating the position of objects after linear self-motion. To determine the source of these errors, we measured errors in remembered target position with or without passive lateral translations. Self-motion was presented both visually (simulated in virtual reality) and physically (on a 6-DOF motion platform). People underestimated targets' eccentricity in general even when just asked to remember them for a few seconds (5-7 seconds), with larger underestimations of more eccentric targets. We hypothesized that updating errors would depend on target eccentricity, which was manifested as errors depending not only on target eccentricity but also the observer's movement range. When updating the position of targets within the range of movement (such that their actual locations crossed the viewer's midline), people overestimated their change in position relative to their head/body compared to when judging the location of objects that were outside the range of movement and therefore did not cross the midline. We interpret these results as revealing changes in the efficacy of spatial updating depending on participant's perception of self-motion and the perceptual consequences for targets represented initially in one half of the visual field having to be reconstructed in the opposite hemifield.