Prototype identification and categorization of incomplete figures by pigeons.

Previous research has shown that pigeons, unlike humans, cannot identify prototypes after training with corrupted exemplars. In the present experiment, pigeons were initially trained to discriminate between examples of a degraded square and a degraded triangle. The pigeons then received a transfer test in extinction comprised of novel examples of the degraded square and triangle, and the prototype square and triangle. The pigeons successfully categorized both the novel examples of the degraded figures and the underlying prototypes. These results suggest that aspects of categorization and prototype identification may be shared across species.