Imagining physically impossible self-rotations: geometry is more important than gravity

Previous studies found that it is easier for observers to spatially update displays during imagined self-rotation versus array rotation. The present study examined whether either the physics of gravity or the geometric relationship between the viewer and array guided this self-rotation advantage. Experiments 1–3 preserved a real or imagined orthogonal relationship between the viewer and the array, requiring a rotation in the observerʹs transverse plane. Despite imagined self-rotations that defied gravity, a viewer advantage remained. Without this orthogonal relationship (Experiment 4), the viewer advantage was lost. We suggest that efficient transformation of the egocentric reference frame relies on the representation of body–environment relations that allow rotation around the observerʹs principal axis. This efficiency persists across different and conflicting physical and imagined postures.