Spatial reference systems in the comprehension of rotational motion. 
In certain simple rotations of objects, the orientation of the axis and planes of rotation can determine whether people are able to visualize the motion or perceive it as simple and coherent.  This finding affords the opportunity to investigate the spatial reference systems used to define the orientation of the axis and planes of rotation.  The results of two experiments suggest that the permanent environment is the primary reference system, apart from the rotating object, used for this purpose.  Subjects also were able to use a local spatial environment to determine the orientation of the motion; some subjects were particularly adept at this.  The viewer perspective, in contrast, was irrelevant as a reference system in these experiments.  These results argue strongly for the primacy of environmental reference systems in the perception and imagination of orientation and extend the set of findings common between the comprehension of rotational motion and orientation-sensitive form perception.