It was decided, for reasons expounded upon below, to do so by constructing stimuli consisting of two silhouettes, one of which is the lamella's facsimile and the other its mirror image (enantiomorph).
When, after being shown an initiating stimulus, the subject is required to respond to a symmetrical pair of silhouettes, either its facsimile or its enantiomorph may be chosen.
(i) The measure of consistency of the two responses: That is, whether or not the same silhouette (either facsimile or its enantiomorph) was chosen on both presentations, and
Each card showed one of the two alternative arrangements of its facsimile and enantiomorph silhouettes.
Furthermore, as the sloping stimuli are more readily confused, the two postulated enantiomorphs by means of which each stimulus is encoded must differ much more markedly in the case of stimuli in the fronto-parallel plane than in the case of the stimuli in inclined planes.
After presentation of the last lamella the participant was presented with a set of 60 cards, 15 of which bore depictions of the stimulus pentagons as they would appear in the fronto-parallel plane, 15 of which bore enantiomorphs of these depictions, and 30 of which portrayed pentagons unrelated to the pentagons used as stimuli.
Thus three scores were obtained in response to the facsimile depictions and three to their enantiomorphs. Table 1 presents the mean group scores obtained.
It incorporates an assumption that the confusability of enantiomorphs indicates that enantiomorphs are used to encode the orientation of planes of stimuli with respect to the fronto-parallel plane.