1096 Memory, Development of Schneider W and Bjorklund DF (1998) Memory. In: Kuhn Schneider W and Pressley M (1997) Memory Development D and Siegler RS (eds) Handbook of Child Psychology, between 2 and 20, 2nd edn. Mahwah, NJ: Lawrence vol. 2, Cognition, Perception, and Language, 5th edn, Erlbaum. pp. 467±521. New York, NY: John Wiley. Memory, Long-term Introductory article Alan Richardson-Klavehn, Goldsmiths College, University of London, London, UK Robert ABjork, University of California, Los Angeles, USA CONTENTS Definition and classification of long-term memory The constructive character of long-term memory The dynamic character of long-term memory Conclusion Long-term memory is central to cognitive function- interconnected and cannot be understood in ing. Taking a wide variety of forms, from skills to isolation from each other. (See Information Pro- general knowledge to memory for personal experi- cessing) ences, it is characterized by dynamic interactions between encoding and retrieval processes and by constructive processes, and thus differs fundamen- Distinguishing between Short-term and tally from current human-made information storage Long-term Memory systems. In everyday discourse, long-term memory is usu- ally distinguished from short-term memory in DEFINITION AND CLASSIFICATION OF terms of the time that has elapsed since information LONG-TERM MEMORY was encoded. Moreover, it is not unusual to find memory that persists over days or weeks being The ability to retain information over long periods described as short-term memory. In psychology, is fundamental to intelligent thought and behavior. however, the terms long-term and short-term Memory is the `glue', in effect, that holds our intel- memory have come to have specialized meanings lectual processes together, from perception, atten- that stem from a distinction made by William tion, and language, to reasoning, decision-making, James in 1890. James observed that our conscious- and problem-solving. Memory also plays a critical ness is not just of the immediate present: the infor- role in social and emotional functioning, because mation that we currently attend to lingers in our sense of who we and other people are is dis- consciousness for some period of time. He called tilled from factual and autobiographical informa- this lingering consciousness primary memory, and tion in our memories. The study of memory, distinguished it from secondary memory, which therefore, occupies a central position in the cogni- occurs when information has left consciousness tive sciences. but returns to it again later. Thus, secondary Broadly, memory can be broken into three stages memory involves retrieval in a way that primary of information processing: (1) encoding, the trans- memory does not. formation of information into a form retainable in James's distinction is not simply one of retention memory; (2) storage, the holding of information interval. It would, theoretically, be possible to in memory across a time interval; and (3) retrieval, retain information in primary memory indefinitely the accessing of information from storage after a as long as one's attention remained focused on that time interval and the use of that information to information (i.e., as long as the information was guide thought and behavior. This distinction be- rehearsed). Conversely, information that leaves tween stages is important but ± as clarified later ± consciousness and then returns to it is retrieved encoding and retrieval processes are intimately from secondary memory, even if retrieval occurs Memory, Long-term 1097 only seconds later. Thus the distinction between example, we sometimes experience the strong short-term (primary) and long-term (secondary) sense that we have met someone before, without memory as used by psychologists is a qualitative being able to recollect where and when we met one, not a simple quantitative one based on reten- them, or anything else about them. The recollec- tion interval. In recent years, Alan Baddeley has tion/familiarity distinction is closely associated introduced the term working memory to refer to with George Mandler and Larry Jacoby. A related short-term memory, which emphasizes its role in distinction, between remembering and knowing, manipulating ± as well as maintaining in con- has been made by Tulving and by John Gardiner. sciousness ± a variety of kinds of information. (See (See Semantic Memory: Computational Models; James, William; Working Memory) Episodic Memory, Computational Models of; Autobiographical Memory; Knowledge Repre- Varied Forms of Long-term Memory sentation, Psychology of) A final important distinction is between explicit As with the short- versus long-term memory dis- and implicit memory. Explicit memory refers to tinction, the main distinctions between forms of conscious awareness of events in one's personal long-term memory involve reference to conscious- past that accompanies deliberate attempts to think ness. The distinction between declarative and pro- back to those events. Implicit memory refers to cedural memory originated in computer science, influences of past events on one's current behavior where stored data structures were distinguished that occur involuntarily or unintentionally, often from stored programs specifying how the data without any current awareness of the relevant were manipulated. Psychologists borrowed these prior events. This distinction, closely associated terms to capture a distinction made by the phil- with Daniel Schacter and Peter Graf, can be traced osopher Gilbert Ryle in 1949, between knowing back to similar distinctions by Hermann Ebbin- that and knowing how. Declarative memory involves ghaus, who published the first experimental stud- knowing consciously that particular events ies of memory in 1885, and by a number of other happened in one's past, or that particular facts are influential thinkers going back to Rene Descartes in true (e.g., Paris is the capital of France). Procedural 1649. (See Descartes, ReneÂ; Ebbinghaus, Her- memory, on the other hand, involves knowing mann) how to manipulate mental or physical objects. It must be noted that none of the foregoing dis- Such knowledge is not necessarily consciously tinctions is universally accepted. First, none is en- accessible and very difficult to communicate ver- tirely clear-cut. For example, Paul Kolers and bally. Explaining to someone how to ride a bicycle, Henry Roediger have questioned the procedural/ for example, offers them scant assistance in learn- declarative distinction, arguing that all forms of ing that skill. Practicing such a skill is essential to its memory involve the modification of procedures learning. The declarative/procedural distinction is for manipulating information. And Schacter, Alan closely associated with John R. Anderson and Larry Richardson-Klavehn and others have pointed out Squire. (See ACT; Skill Acquisition: Models; that the explicit/implicit memory distinction is Automaticity; Implicit Learning; Skill Learning; blurred by cases when conscious awareness of Knowledge Representation, Psychology of) events in one's personal past comes about without Within declarative memory, episodic memory is any deliberate attempt to retrieve those events, a distinguished from semantic memory. Episodic phenomenon termed involuntary explicit memory memory involves awareness of particular events or involuntary conscious memory. in one's personal autobiography, whereas semantic Second, a controversial question is whether these memory involves knowledge of language, categor- distinctions imply different information-process- ies and concepts, and facts. This distinction is ing mechanisms, with different bases in the struc- closely associated with Endel Tulving. Within epi- ture and function of the brain. Support for the latter sodic memory, in turn, recollection is distinguished view comes from research by Brenda Milner, Eliza- from familiarity. Recollection involves re-experien- beth Warrington, Lawrence Weiskrantz and others cing the particular contextual details of a past on the amnesia (memory loss) that results from event, such as the tone of voice in which a state- damage to limbic system structures in the brain ment was uttered in the kitchen at nine o'clock (the hippocampus, portions of the thalamus, and yesterday morning. Familiarity involves the know- connected structures). This memory loss is select- ledge that a current situation bears some relation- ive, resulting in dissociations between different ship to a past event, without awareness of the measures of memory. For example, short-term particular contextual details of that event. For memory is largely spared, whereas the acquisition 1098 Memory, Long-term of new long-term memories is severely impaired, stored. With human memory, by contrast, encod- and the declarative and explicit forms of long-term ing new information depends on retrieval of in- memory are impaired much more than the proced- formation already in memory. The computer ural and implicit forms. Dissociations that are simi- metaphor also suggests that the act of retrieving lar in some respects are observed in dementias such an item makes that item no more and no less ac- as Alzheimer and Huntington diseases, as well cessible in the future, and does not affect the acces- as in the memory loss that accompanies normal sibility of other items. With human memory, by aging. Such dissociations have led some, including contrast, retrieval renders the retrieved informa- Schacter, Squire, and Tulving, to argue