1. A method for controlling access to a protected resource, the method comprising the steps of: presenting a user with a plurality of primed stimuli during a priming phase; presenting said user with a plurality of degraded versions of a subset of said primed stimuli and with a plurality of degraded versions of non-primed stimuli during an authentication phase; receiving an identification from said user of said degraded versions of said primed stimuli and said degraded versions of said non-primed stimuli; and authenticating said user based upon a number of correct identifications of said degraded versions of said primed stimuli.