Optimizing the ULV-VFQ for Clinical Use Through Item Set Reduction: Psychometric Properties and Trade-Offs

Abstract

Seven experiments tested whether human navigation depends on enduring representations,or on momentary egocentric representations that are updated as one moves. Human subjectspointed to unseen targets, either while remaining oriented or after they had been disorientedby self-rotation. Disorientation reduced not only the absolute accuracy of pointing to allobjects (`heading error') but also the relative accuracy of pointing to different objects (`con®gurationerror'). A single light providing a directional cue reduced both heading and con®gurationerrors if it was present throughout the experiment. If the light was present duringlearning and test but absent during the disorientation procedure, however, subjects showedlow heading errors (indicating that they reoriented by the light) but high configuration errors(indicating that they failed to retrieve an accurate cognitive map of their surroundings). TheseEndings provide evidence that object locations are represented egocentrically. Nevertheless,disorientation had little effect on the coherence of pointing to different room corners, suggestingboth (a) that the disorientation effect on representations of object locations is not due to theexperimental paradigm and (b) that room geometry is captured by an enduring representation.These Endings cast doubt on the view that accurate navigation depends primarily on anenduring, observer-free cognitive map, for humans construct such a representation ofextended surfaces but not of objects. Like insects, humans represent the egocentric distancesand directions of objects and continuously update these representations as they move. Theprincipal evolutionary advance in animal navigation may concern the number of unseentargets whose egocentric directions and distances can be represented and updated simultaneously,rather than a qualitative shift in navigation toward reliance on an allocentric map.