Explicit and implicit remembering: when is learning preserved in amnesia?

Amnesic patients can learn and retain a variety of skills. To investigate what distinguishes tasks that are within the learning abilities of amnesic patients from those that are not, we administered two tests to individuals with Korsakoff's syndrome and two control groups. One was a visual reaction time task with an embedded repeating sequence of stimulus positions. Response times of Korsakoff patients indicated that they learned this sequence and retained it normally for a week. The second task was a tactual stylus maze in which all blind alleys were blocked. Korsakoff patients were impaired in learning this maze, as assessed by the time required to trace it. Differences between the two tasks are outlined and the implications of these differences are discussed.