The perception and recognition of faces forms a topic which interests cognitive psychologists for a number of reasons. First, our individual abilities to recognize several hundreds (perhaps thousands) of faces demonstrates the extraordinary power and sensitivity of our visual memory system. Second, due to the uniqueness of facial appearance, the face plays the same key role as the fingerprint in forensic identification, yet we have no simple way to reveal the image of the face in the witnesses' mind. Cognitive psychologists have an important role to play in determining the most effective ways of eliciting this hidden knowledge.