Flipping and spinning: spatial transformation procedures in the identification of rotated natural objects.

The proposal that identification of inverted objects is accomplished by either a relatively slow rotation in the picture plane or a faster rotation in the depth plane about the horizontal axis was tested. In Experiment 1, subjects decided whether objects at 0 degree or 180 degrees corresponded to previously learned normal views of the upright objects, or were mirror images. Instructions to mentally flip an inverted object in the depth plane to the upright produced faster decision times than did instructions to mentally spin the object in the picture plane. In Experiment 2, the effects of orientation were compared across an object-naming task and a normal-mirror task for six orientations from 0 degree to 300 degrees. In the normal-mirror task, objects at 180 degrees were cued for rotation in the picture plane or in the depth plane in equal numbers. The naming function for one group of subjects did not differ from the normal-mirror function where inverted objects had been mentally rotated to the upright. For both functions, response time (RT) increased linearly from 0 degree to 180 degrees and the slopes did not differ. The naming function for a second group of subjects did not differ from the normal-mirror function where inverted objects had been mentally flipped to the upright. For both functions, RT increased linearly at a similar rate from 0 degree to 120 degrees, but decreased from 120 degrees to 180 degrees. The results are discussed in terms of theories of orientation-specific identification.