Stored representations of three-dimensional objects in the absence of two-dimensional cues

Object recognition was studied in human subjects to determine whether the s torage of the visual objects was in a two-dimensional or a three-dimensiona l representation. Novel motion-based and disparity-based stimuli were gener ated in which three-dimensional and two-dimensional form cues could be mani pulated independently. Subjects were required to generate internal represen tations from motion stimuli that lacked explicit two-dimensional cues. Thes e stored internal representations were then matched against internal three- dimensional representations constructed from disparity stimuli. These new s timuli were used to confirm prior studies that indicated the primacy of two -dimensional cues for view-based object storage. However, under tightly con trolled conditions for which only three-dimensional cues were available, hu man subjects were also able to match an internal representation derived fro m motion to that of disparity. This last finding suggests that there is an internal storage of an object's representations in three dimensions, a tene t that has been rejected by view-based theories. Thus, any complete theory of object recognition that is based on primate vision must incorporate thre e-dimensional stored representations.