Prosopagnosia and object agnosia without covert recognition.

Investigations of the visual recognition abilities of the patient M.S. are reported. M.S. is unable to achieve overt recognition of any familiar faces, and many everyday objects. In Task 1 he showed semantic priming from name primes but not from face primes in a name recognition task. In Task 2 he showed no advantage in learning true (face + correct name) rather than untrue (face + someone else's name) pairings of faces and names. In Task 3 semantic priming of lexical decision was only found for object picture primes that M.S. was able to recognize overtly. In Task 4 faster matching of photographs of familiar than unfamiliar objects was only found for objects that M.S. was able to recognize overtly. These findings demonstrate an absence of covert recognition effects for M.S., consistent with the view that his impairment is primarily "perceptual" in nature.