When are viewpoint costs greater for silhouettes than for shaded images?

Previous studies of object recognition have shown efficient recognition of silhouettes, suggesting that much of the information used to recognize objects resides in the outline. These studies, however, have used objects that contain many components, which provide redundant information. In this study, we examined recognition of silhouettes of less-complex objects, so that redundant information was reduced. We found that viewpoint generalization costs (the decrement of performance when recognizing nonstudied views) were greater for silhouettes than for shaded images, even when the same qualitative components were visible in the outline of both studied and nonstudied views. Thus, silhouettes do not always allow for view generalization as efficiently as do shaded images.