Updating egocentric representations in human navigation

Seven experiments tested whether human navigation depends on enduring repre sentations, or on momentary egocentric representations that are updated as one moves. Human subjects pointed to unseen targets, either while remaining oriented or after they had been disoriented by self-rotation. Disorientati on reduced not only the absolute accuracy of pointing to all objects ('head ing error') but also the relative accuracy of pointing to different objects ('configuration error'). A single light providing a directional cue reduce d both heading and configuration en:ors if it was present throughout the ex periment. If the light was present during learning and test but absent duri ng the disorientation procedure, however, subjects showed low heading error s (indicating that they reoriented by the light) but high configuration err ors (indicating that they failed to retrieve an accurate cognitive map of t heir surroundings). These findings provide evidence that object locations a re represented egocentrically. Nevertheless, disorientation had little effe ct on the coherence of pointing to different room corners, suggesting both (a) that the disorientation effect on representations of object locations i s not due to the experimental paradigm and (b) that room geometry is captur ed by an enduring representation, These findings cast doubt on the view tha t accurate navigation depends primarily on an enduring, observer-free cogni tive map, for humans construct such a representation of extended surfaces b ut not of objects. Like insects, humans represent the egocentric distances and directions of objects and continuously update these representations as they move. The principal evolutionary advance in animal navigation may conc ern the number of unseen targets whose egocentric directions and distances can be represented and updated simultaneously, rather than a qualitative sh ift in navigation toward reliance on an allocentric map. (C) 2000 Published by Elsevier Science B.V. All rights reserved.