The explicit/implicit memory distinction is one of several hypothesized memory dichotomies. As first proposed, the distinction was between tasks that require conscious recollection of experience (explicit) and tasks in which performance is facilitated by previous experience but for which recollection of that experience is not required (Graf & Schacter, 1985). As such, the distinction is neutral regard­ ing the question of underlying memory systems. However, several authors have postulated that performance on implicit memory tasks is mediated by a different underlying memory system than performance on explicit memory tasks (Gabrieli, Milberg, Keane, & Corkin, 1990; Schacter, 1990; Squire, 1987; Tulv­ ing & Schacter, 1990), and a central question in current memory research regards the extent to which the experimental evidence requires that independent systems subserve explicit and implicit memory.