Demonstration of a mental analog of an external rotation

Subjects imagined a designated two-dimensional shape rotating within a blank, circular field at a self-determined rate. At some point during the mental rotation, a test shape was presented at one of 12 picture-plane orientations, and the subject was required to determine as rapidly as possible whether the test shape was the same as the originally designated shape or was its mirror image. When the test shape was presented in the expected orientation (the orientation assumed to correspond to the current orientation of the rotating internal representation), reaction time was short and constant, regardless of the angular departure of that orientation from a previously trained position. This was true even when the test shape was presented in an orientation which had not previously been tested. When the test shape was presented at some other. unexpected orientation, reaction time increased linearly with the angular difference between the expected orientation and the orientation of the test shape. It is argued that these results provide a demonstration of the "analog" nature of mental rotation.