Agnosia for object orientation: implications for theories of object recognition.

Instances in which objects are copied accurately, but are dramatically rotated relative to the original, have been interpreted as evidence for viewpoint-independent accounts of the object recognition process. In two case reports, we demonstrate that patients who show rotation in copying also show difficulties in informing the examiner of the canonical orientation of known objects. In copying rotated versions of familiar objects, one subject showed a tendency to copy them in their canonical upright orientation, and both subjects copied non-representational line drawings with their principal axis vertically aligned, and with the irregular end pointing 'upwards'.