We introduce an approach for how spatial reasoning can be conceived as verbal reasoning. We describe a theory of how humans construct a mental representation given onedimensional spatial relations. In this construction process objects are inserted in a dynamic structure called a queue which provides an implicit direction. The spatial interpretation of this direction can be chosen freely. This implies that choices in the process of constructing a mental representation influence the result of deductive spatial reasoning. To derive the precise rules for the construction process we employ the assumption that humans try to minimize their cognitive effort, and a cost measure is introduced to judge the efficiency of the construction process. From this we deduce how the queue should be constructed. We discuss empirical evidence for this approach as well as a computational implementation of the construction process.