Stored Representations of three-Dimensional Objects in the Absence of Two-Dimensional Cues

Object recognition was studied in human subjects to determine whether the storage of the visual objects was in a two-dimensional or a three-dimensional representation. Novel motion-based and disparity-based stimuli were generated in which three-dimensional and two-dimensional form cues could be manipulated independently. Subjects were required to generate internal representations from motion stimuli that lacked explicit two-dimensional cues. These stored internal representations were then matched against internal three-dimensional representations constructed from disparity stimuli. These new stimuli were used to confirm prior studies that indicated the primacy of two-dimensional cues for view-based object storage. However, under tightly controlled conditions for which only three-dimensional cues were available, human subjects were also able to match an internal representation derived from motion to that of disparity. This last finding suggests that there is an internal storage of an object's representations in three dimensions, a tenet that has been rejected by view-based theories. Thus, any complete theory of object recognition that is based on primate vision must incorporate three-dimensional stored representations.