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Three experiments investigated the frame of reference used in memory to represent vertical spatial layouts perceiv-able from a single viewpoint. We tested for the selection of three different reference systems: the body orientation, the visualvertical of the surrounding room, and the direction of gravity. Participants learned and retrieved differently colored objects ona vertical board with body and room orientations varying in relation to gravity and each other systematically. Across all threeexperiments participants were quicker or more accurate in memory recall when they saw the vertical spatial layout in the sameorientation in relation to their body vertical as during learning, irrespective of the direction of gravity or visual room upright.These results indicate that spatial long-term memories for small-scale vertical relations are mainly defined in an egocentricreference system with respect to the body vertical despite the availability of alternative highly salient allocentric referencedirections.

People reason about possibilities routinely, and reasoners caninfer “modal” conclusions, i.e., conclusions that concern whatis possible or necessary, from premises that make no mentionof modality. For instance, given that Cullen was born in NewYork or Kentucky, it is intuitive to infer that it’s possible thatCullen was born in New York, and a recent set of studies onmodal reasoning bear out these intuitions (Hinterecker,Knauff, & Johnson-Laird, 2016). What explains the tendencyto make modal inferences? Conventional logic does not applyto modal reasoning, and so logicians invented manyalternative systems of modal logic to capture valid modalinferences. But, none of those systems can explain theinference above. We posit a novel theory based on the ideathat reasoners build mental models, i.e., iconic simulations ofpossibilities, when they reason about sentential connectivessuch as and, if, and or (Johnson-Laird, 2006). The theoryposits that reasoners represent a set of conjunctivepossibilities to capture the meanings of compound assertions.It is implemented in a new computational process model ofsentential reasoning that can draw modal conclusions fromnon-modal premises. We describe the theory andcomputational model, and show how its performance matchesreasoners’ inferences in two studies by Hinterecker et al.(2016). We conclude by discussing the model-based theory inlight of alternative accounts of reasoning.