(Failing) To See or To Remember

A few seconds after being shown an image, an amnesiac is asked to find a match for it within a group of new images. She fails to do it. What is wrong with her? Is it just her memory? Does she also have a perceptual problem? How should we distinguish a purely mnemonic from a deficit that is also perceptual?

“Simple,” you might say. “Do a new experiment. Present the amnesiac simultaneously with the sample and the group of images, and ask her to find the match. If she finds it, the deficit is mnemonic. If she doesn’t, it might also be perceptual.”

Unfortunately, things are not as simple as this.