Preattentive perception of elementary three-dimensional shapes.

Experiments in which a single target pattern is discriminated from multiple background distractors show that certain shaded, two-dimensional (2-D) stimuli consistent with a top-lit, polyhedral interpretation can be processed fast (< 80 msec) and in parallel. Unshaded line drawings of the same shapes, however, are processed serially. Strong pop-out asymmetries and control experiments involving shaded patterns that do not have familiar 3-D interpretations suggest that such fast, parallel processing is dependent upon perception 3-D shape. Furthermore, this process can be influenced by contextual scene information, in a manner that is dependent upon whether the additional cues contribute to the perception of a consistent 3-D scene.