Mental rotation: an examination of assumptions.

Since first presented by Shepard and Metzler, Science 1971, 171: 701-703, mental rotation has been described as a rotary transformation of a visual stimulus allowing it to be represented in a new orientation. For a given stimulus, the transformation is thought to occur at a constant speed, though speed may vary between stimuli; three-dimensional abstract shapes made out of blocks tend to be rotated much more slowly than alphanumeric characters or line drawings of common objects. Rotation is also presumed to be performed through the shortest angle.

Asymmetric response time functions during left-/right-facing discriminations of rotated objects: The short and the long of it.

When deciding if a rotated object would face to the left or to the right, if imagined at the upright, mental rotation is typically assumed to be carried out through the shortest angular distance to the upright prior to determining the direction of facing. However, the response time functions for left- and right-facing objects are oppositely asymmetric, which is not consistent with the standard explanation. Using Searle and Hamm's individual differences adaption of Kung and Hamm's Mixture Model, the current study compares the predicted response time functions derived when assuming that objects are rotated through the shortest route to the upright with the predicted response time functions derived when assuming that objects are rotated in the direction they face.

Individual differences in the mixture ratio of rotation and nonrotation trials during rotated mirror/normal letter discriminations.

Mental rotation is thought to underlie the increase in response times (RTs) for deciding whether rotated letters are normal or mirrored versions. However, mental rotation predicts a linear increase in RTs, whereas the mirror/normal letter discrimination task typically produces a curved function. Recently, Kung and Hamm suggested that this curved function results from a mixture of trials in which mental rotation is employed and trials in which it is not.