Nonholistic processing in mental rotation: Some suggestive evidence

A series of experiments, using a modification of the Shepard and Metzler mental rotation task, was performed to investigate Shepard’s “holistic rotation” hypothesis. Effective figural complexity was manipulated in the experiments in two distinct ways. In one manipulation, blocks were added to the standard 10-blockfigures. In the other manipulation, the figures used and the direction of angular rotation were restricted so that some featural information in the figures was redundant, that is, unnecessary for the discrimination task at hand. There were two major conclusions. First, when figural complexity is effectively manipulated, it has a powerful effect on the “speed of mental rotation,” as measured by the slope of the curve relating reaction time to angular disparity. Second, it is possible, by ignoring featural redundancy, to construct experimental paradigms in which “complexity” of figures is apparently manipulated but has no effect on speed of mental rotation. This fact provides a possible explanation of why some previous experiments have failed to find a complexity effect in mental rotation.