Learning About Categories in the Absence of Training: Profound Amnesia and the Relationship Between PerceptualCategorization and Recognition Memory

Previous evidence suggests that amnesics can categorize stimuli as well as normal individuals but are significantly worse at recognizing those stimuli. In an extreme case, a profoundly amnesic individual, E.P., was found to have near-normal categorization, yet, unlike most amnesics, was unable to recognize better than chance. This evidence has been used to argue against the possibility that a common memory system underlies these cognitive processes. However, we provide evidence that the experimental procedures typically used to test amnesic individuals may be flawed in that initial exposure to category members may be unnecessary to observe accurate categorization of test stimuli. We experimentally "induced" profound amnesia in normal individuals by telling them they had viewed subliminally presented stimuli, which were never actually presented. Using the same experimental paradigm used to test amnesics, we observed that participants' recognition performance was completely at chance, as should be expected, yet categorization performance was quite good.