People often solve spatially presented cognitive problems more
easily than their nonspatial counterparts. We explain this phenomenon
by characterizing space as an inter-modality that provides
common structure to different specific perceptual modalities. The
usefulness of spatial structure for knowledge processing on different
levels of granularity and for interaction between internal and external
processes is described. Map representations are discussed as examples
in which the usefulness of spatially organized symbols is particularly
evident. External representations and processes can enhance internal
representations and processes effectively when the same structures
and principles can be implicitly assumed.