Non-visual information in structure-from-motion.

We examined whether non-visual signals improve visual perception of three-dimensional structure-from-motion. Observers discriminated curvature in quadratic surfaces defined by random dot cinematograms with limited lifetime. They either explored visually a static surface by making head movements that were fed back to the display (HM condition) or they viewed statically the same surface which now rotated (NHM condition). Both conditions showed a clear build-up of performance as lifetime increases, but with different time constants for the HM and NHM condition. A second experiment showed that these differences could not be caused by differences in motion detection for the HM and NHM conditions. We suggest that non-visual information is combined with visual information at a high stage of visual processing, and that it does not mainly serve as input for a retinal stabilization process.