RESTRICTED ABILITY TO RECOVER 3-DIMENSIONAL GLOBAL MOTION FROM ONE-DIMENSIONAL MOTION SIGNALS - PSYCHOPHYSICAL OBSERVATIONS

We tested human ability to recover the 3D structure and motion informa tion from time-varying images where only In motion cues were available . Under these conditions, observers exhibit poor performance in discri minating between two perpendicular axes of rotation, or discriminating between rigid and non-rigid 3D motion. This behavior of the visual sy stem is to be contrasted with the good depth from motion performance e xhibited when 2D motion cues are given in the image, as was found prev iously in numerous studies, and also in the work presented here. In a related paper, we suggest a theoretical framework in which to understa nd this differential performance on the basis of the two types of moti on cues (1D vs 2D). Our findings are consistent with those of previous studies of frontoparallel motion, where it was shown that in many cas es, the In cues alone were not integrated by the visual system into th e correct global motion percept. This accumulating evidence suggests t hat oriented (1D) motion detectors alone cannot account for observed h uman performance of global motion perception, and that the role of uni ts such as point or endpoint detectors should be studied further.