The research described in this proposal investigates human spatial memory. The long-term goal of the project is to understand how spatial relations among objects in the environment are represented in memory and how remembered spatial relations are used to guide navigation. The specific aims of the project are to advance the scientific understanding of (a) how location and orientation are updated in memory as people locomote in a previously learned environment; (b) the mental representations and processes used in spatial pointing tasks; (c) the extent to which spatial relations are represented more strongly in directions congruent than in directions incongruent with intrinsic axes of a spatial layout; (d) the acquisition of memories of largescale environments; (e) whether learning a new environment produces multiple representations in memory; and (t) the nature of spatial memories acquired from non-visual modalities, and how they compare to spatial memories acquired visually. Participants will learn locations of objects in spaces ranging in size from a table-top to a large city park. Layouts will be learned by visual inspection, visually guided locomotion, or manual exploration without visual guidance. After learning the layouts, participants will take part in tasks that require them to point to target objects from their actual location or from imagined standing locations and facing directions, to discriminate familiar and novel views of a recently learned spatial layout from views of other spatial layouts, or to decide whether objects are in one layout vs. another. Individual differences, including gender-related effects, will be examined in all experiments. This basic science provides a theoretical and empirical foundation for understanding individual differences in spatial ability, and the debilitating deficits in spatial memory created by stroke, traumatic brain injury, and dementia.