An eye movement analysis of "mental rotation" of simple scenes

Participants saw a standard scene of three objects on a desktop and then judged whether a comparison scene was either the same, except for the viewpoint of the scene, or different, when one or more of the objects either exchanged places or were rotated around their center. As in Nakatani, Pollatsek, and Johnson (2002), judgment times were longer when the rotation angles of the comparison scene increased, and the size of the rotation effect varied for different axes and was larger for same judgments than for different judgments. A second experiment, which included trials without the desktop, indicated that removing the desktop frame of reference mainly affected the y-axis rotation conditions (the axis going vertically through the desktop plane). In addition, eye movement analyses indicated that the process was far more than a simple analogue rotation of the standard scene. The total response latency was divided into three components: the initial eye movement latency, the first-pass time, and the second-pass time. The only indication of a rotation effect in the time to execute the first two components was for z-axis (plane of sight) rotations. Thus, for x- and y-axis rotations, rotation effects occurred only in the probability of there being a second pass and the time to execute it. The data are inconsistent either with an initial rotation of the memory representation of the standard scene to the orientation of the comparison scene or with a holistic alignment of the comparison scene prior to comparing it with the memory representation of the standard scene. Indeed, the eye movement analysis suggests that little of the increased response time for rotated comparison scenes is due to something like a time-consuming analogue process but is, instead, due to more comparisons on individual objects being made (possibly more double checking).