This chapter gives an overview of our ongoing experimental research in the MeMoSpace project, concerning the cognitive processes underlying human spatial reasoning. Our theoretical background is mental model theory, which conceives reasoning as a process in which mental models of the given information are constructed and inspected to solve a reasoning task. We first report some findings of our previous work and then two new experiments on spatial relational inference, which were conducted to investigate well-known effects from relational and syllogistic reasoning. (1) Continuity effect: n-term-series problems with continuous (W r1 X, X r2 Y, Y r3 Z) and semi-continuous (X r2 Y, Y r3 Z, W r1 X) premise order are easier than tasks with discontinuous order (Y r3 Z, W r1 X, X r2 Y). (2) Figural bias: the order of terms in the premises (X r Y, Y r Z or Y r X, Z r Y) effects the order of terms in the conclusion (X r Z or Z r X). In the first experiment subjects made more errors and took more...