This third volume documents the results achieved within a priority program on spatial cognition funded by the German Science Foundation (DFG). The 23 revised full papers presented went through two rounds of reviewing and improvement and reflect the increased interdisciplinary cooperation in the area. The papers are organized in topical sections on routes and navigation, human memory and learning, spatial representation, and spatial reasoning.

Spatialcognitionisconcernedwiththewayshumans,animals,ormachinesthink about real or abstract space and also with the ways spatial structures can be used for reasoning. Thus, space is considered both, as an object of cognition and as ameans of cognition. Spatial cognition is an interdisciplinary research areainvolvingapproachesfromarti?cialintelligence,cognitivepsychology,ge- raphy, mathematics, biology, design, theoretical computer science, architecture, andphilosophy.Researchonspatialcognitionhasprogressedrapidlyduringthe past few years. The disciplines contributing to the ?eld have moved closer - getherandbegintospeakacommonlanguage.Theyhavefoundwaysofmerging theresearchresultsobtainedthroughdi?erentapproaches.Thisallowsfordev- oping more sophisticated hybrid approaches that overcome intrinsic limitations of the individual disciplines. Research on spatial cognition has drawn increased attention in recent years foratleastthreedi?erentreasons:(1)basicresearchdimension:thereisagr- ing awareness of the importance of spatial cognitive abilities in biological s- tems, speci?cally with respect to perception and action, to the organization of memory, and to understanding and producing natural language; (2) compu- tionaldimension:spatialrepresentationsandspatialinferencemayprovidesu- ablelimitationsto enhancethe computationale? ciencyforalargeandrelevant class of problems; (3) application dimension: a good understanding of spatial processes is essential for a wide variety of challenging application areas incl- ing Geographic Information Systems (GIS), pedestrian and vehicle navigation aids,autonomousrobots,smartgraphics,medicalsurgery,informationretrieval, virtual reality, Internet navigation, and human-computer interfaces. This is the second volume published in the framework of the Spatial Cog- tion Priority Program. It augments the results presented in Freksa et al. 1998.

Research on spatial cognition is a rapidly evolving interdisciplinary enterprise for the study of spatial representations and cognitive spatial processes, be they real or abstract, human or machine. Spatial cognition brings together a variety of - search methodologies: empirical investigations on human and animal orientation and navigation; studies of communicating spatial knowledge using language and graphical or other pictorial means; the development of formal models for r- resenting and processing spatial knowledge; and computer implementations to solve spatial problems, to simulate human or animal orientation and navigation behavior, or to reproduce spatial communication patterns. These approaches can interact in interesting and useful ways: Results from empirical studies call for formal explanations both of the underlying memory structures and of the processes operating upon them; we can develop and - plement operational computer models obeying the relationships between objects and events described by the formal models; we can empirically test the computer models under a variety of conditions, and we can compare the results to the - sults from the human or animal experiments. A disagreement between these results can provide useful indications towards the re nement of the models.