Imagined spatial transformation of one's body.

Abstract

This study examined two related phenomena: (a) the judgment of whether a human body part belongs to the left or right half of the body and (b) the imagined spatial transformation of one's body.In three experiments, observers made left-right judgments of a part of a body whose orientation differed from their own by a rotation about one of 13 axes.To do so, they imagined themselves passing to the orientation of the stimulus.Time for (a) left-right judgments and (b) accompanying imagined spatial transformations depended on the extent of the orientation difference (OD) between the observer and stimulus.More important, time for phenomena (a) and (b) depended strongly, and in the same way, on the direction of OD.Further results showed that the rate of imagined spatial transformations can vary strongly for different axes and directions of rotation about an axis.These and other results (e.g., Parsons, 1987a) suggest that temporal and kinematic properties of imagined spatial transformations are more object-specific than could be previously assumed.When similar objects are at the same orientation, people can often readily discriminate differences in the composition and spatial arrangement of the objects' features.However, as the objects differ in orientation, the effort needed to discriminate between identical and just similar pairs increases.Searching for and comparing corresponding features of objects at different orientations can overburden spatial working memory (Parsons, 1986b).One very often finds it more efficient to imagine or to produce physical rotation(s) of one object to an orientation like that of the other (e.g., Hinton & Parsons, 1987;Shepard & Metzler, 1971).This latter fact has been exploited to study both the internal representation of shape (Corballis, Zbrodoff,