The ups and downs of memory

Ever since the classic work of Ebbinghaus (1885/1964), the default view in scientific psychology has been that memory declines over time. Less well-known clinical and laboratory traditions suggest, however, that memory can also increase over time. Ballard (1913) demonstrated that, actually, memory simultaneously increases and decreases over time and thus has not 1 but 2 tendencies. When more than 1 recall test is administered, a later test invariably shows loss of some items remembered earlier (oblivescence), but later tests also invariably show that previously unremembered items are recovered in later tests (reminiscence). Depending on a number of factors (e.g., the stimulus used), the overall balance between reminiscence and oblivescence may be positive (hypermnesia) or negative (amnesia). Modern multitrial recall studies have extensively documented hypermnesic memory in single laboratory sessions and, also, although less frequently, over periods of days, weeks, and even months. With hypermnesic memory now established, hypnosis has been shown not to add anything to regular hypermnesia. This article presents an integration of the scattered literatures, which now, after a century of experimental and clinical effort, coheres into a solid empirical picture, with numerous implications (e.g., for the recovered memory controversy, eyewitness testimony, repression, and subliminal perception).