HOW ARE 3-DIMENSIONAL OBJECTS REPRESENTED IN THE BRAIN

In this report we discuss a variety of psychophysical experiments that explore different aspects of the problem of object recognition and re presentation in human vision. In all experiments, subjects were presen ted with realistically rendered images of computer-generated 3D object s, with tight control over stimulus shape, surface properties, illumin ation, and viewpoint, as well as subjects' prior exposure to the stimu lus objects. Contrary to the predictions of the paradigmatic theory of recognition, which holds that object representations are viewpoint in variant, performance in all experiments was consistently viewpoint dep endent, was only partially aided by binocular stereo and other depth i nformation, was specific to viewpoints that were familiar, and was sys tematically disrupted by rotation in depth more than by deforming the 2D images of the stimuli. The emerging concept of multiple-views repre sentation supported by these results is consistent with recently advan ced computational theories of recognition based on view interpolation. Moreover, in several simulated experiments employing the same stimuli used in experiments with human subjects, models based on multiple-vie ws representations replicated many of the psychophysical results conce rning the observed pattern of human performance.