Optical information and practice in the discrimination of 3-D mirror-reflected objects

Two studies of the discrimination of three-dimensional mirror-reflected objects were concerned with the influence of practice and stimulus information for shape, specifically binocular information and perspective transformations. In the first study subjects made 'same-different' responses to successively presented pairs of real objects, under binocular and monocular viewing conditions. In the second study subjects viewed object pairs on a rotating turntable, in five different displays. Neither binocular information nor perspective transformations contributed to isomorph discrimination. In both studies mental rotation and other less well specified strategies were employed. After practice, in contrast to previous reports, five of the six subjects in these studies produced reaction times unrelated to the orientation difference between the objects. These practice effects may reflect either extremely rapid rotation rates, the detection of rotationally invariant features, or the use of multiple strategies.