| Abstract: | Although it is generally assumed that vision is orientation invariant, that is, that shapes can be recognized regardless of viewing angle, there is little evidence that speaks directly to this issue, and what evidence there is fails to support orientation invariance. We propose an explanation for the previous results in terms of the kinds of shape primitives used by the visual system in achieving orientation invariance: Whereas contours are used at stages of vision that ore not orientation invariant, surfaces and/or volumes are used at stages of vision that are orientation invariant. The stimuli in previously reported studies were wire forms, which can represented only in terms of contour. In four experiments, testing both short-term and long-term memory for shape, we replicated the previous failures of orientation invariance using wire forms, but found relatively good or perfect orientation invariance with equivalently shaped surfaces. |
