DO AMNESICS FORGET FACES PATHOLOGICALLY FAST

In 1978, Huppert and Piercy introduced a general method for comparing forgetting rates across groups differing in their baseline memory perf ormance. The method has since become a standard for measuring rate of forgetting in amnesia. Using this method, amnesic subjects with presum ed damage to midline diencephalic structures have consistently been re ported to forget at a normal rate whereas patients with medial tempora l lobe damage have sometimes been reported to forget pathologically fa st. Conclusions about amnesic forgetting rates using Huppert and Pierc y's procedure, however, are unsafe because the matching procedure resu lts in the shortest mean item-presentation-to-test delay being longer in amnesics than control subjects. A further problem with previous wor k is that frequently the shortest delay at which performance is measur ed is 10 minutes. An alternative procedure to Huppert and Piercy's is outlined which eliminates the matching confound. An experiment was car ried out using this procedure with face stimuli, and with amnesic and control performance matched immediately following study, and then test ed at delays of 5, 12, and 30 minutes. Pathologically fast forgetting was observed in a group of 19 amnesics over the first 5 minutes, but b etween 12 and 30 minutes their controls forgot faster so that the two groups had forgotten the same amount after 30 minutes. A subgroup of n ine Korsakoff patients, with probable damage to midline diencephalic s tructures, showed a similar abnormal forgetting pattern to the remaini ng 10 amnesics, some of whom had medial temporal lobe damage. A retroa ctive interference condition was also included for the 12 minute condi tion at which delay patient and control recognition was mildly and equ ivalently disrupted. For unknown reasons perhaps related to a storage abnormality, amnesics lose face recognition memory sooner in the first 30 minutes of forgetting than do normal people, who show accelerated forgetting later so as to match patients after 30 minutes delay.