On the Representation of Object Structure in Human Vision: Evidence from Diierential Priming of Shape and Location 1 the Problem of Representation

Theories of object representation can be classiied as structural, holistic or hybrid, depending on their approach to the mereology and compositionality of shapes. We tested the predictions of some of the current theories in three experiments, by quantifying the eeects of various priming cues on response times to 3D objects. In experiment 1, there were two possible locations for the stimulus components: left-right and top-bottom. The prime could be identical to the stimulus, identical in location but with diierent parts, identical in the complement of diierently located parts, or altogether diierent. Both location and part identity eeects were signiicant. In experiment 2 we added a part-neutral (empty frame) prime condition; the eeect of location, but not of part, remained signiicant. In experiment 3, which included an additional location-neutral prime condition, only the location eeect, again, was signiicant. These ndings are not entirely compatible either with the structural description theories of representation (which predict priming by \disembodied" parts or geons) or with the holistic theories (which do not predict priming by \shapeless" location on its own). They may be interpreted in terms of a hybrid theory, according to which conjunctions of shape and location are explicitly represented, and therefore amenable to priming. The nature of the memory trace left by perceived objects in the human visual system is a fascinating problem, whose solution would lead both to a better understanding of vision in the brain, and to the development of better artiicial visual systems. From a computational standpoint, the Problem of Representation of object shapes has several distinct aspects. For example, any computational model of object recognition must explain how to represent objects internally in such a manner that the variability of their appearance caused by changing viewing conditions (such as viewpoint or illumination) will not disrupt recognition (Ullman, 1996). In theorizing about human vision, this consideration led to the emergence of two classes of models. On the one hand, there are models that postulate essentially viewpoint-invariant representations, claiming that human performance in recognition does not, by and large, depend on viewpoint