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Abstract:
Amnesics can categorize stimuli as well as normal individuals
but recognize those stimuli significantly worse (Knowlton &
Squire, 1993). An extreme case is E.P., reported by Squire and
Knowlton (1995), who showed near normal categorization, yet, unlike
most amnesics, had such profound amnesia that recognition was
completely at chance. Squire and Knowlton argued that this evidence
ruled out the possibility of a common memory system underlying
these processes. However, we provide evidence that the experimental
paradigm used to test E.P. and other amnesics may be flawed, in
that exposure to stimuli may be unnecessary to observe accurate
categorization performance. In several experiments, 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 E.P. and other amnesics, participants' recognition
performance was completely at chance, as should be expected, yet
categorization performance was quite good.
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