The outer limits of implicit memory

Memory is “implicit” when it is expressed through behavior without an individual’s awareness. Implicit memory is in contrast with various explicit expressions of memory that occur with awareness, such as the experience of recollecting past events. Whereas explicit memory is generally considered robust and varied in expression, standard accounts of implicit memory have focused on its apparent limitations, emphasizing constraints on the types of information it may concern, its duration, the brain regions involved, and the range of behaviors through which it can be expressed. We describe these beliefs about the limitations of implicit memory, and outline how recent research has considerably expanded the scope of implicit memory. By reviewing these “outer limits” of implicit memory, we suggest that it is a robust phenomenon that is operative in a variety of circumstances, has a complex functional neuroanatomy, and is relevant to a wide variety of behaviors concerning many stimulus categories.