Memory: Collective and Individual Approaches

Overview

Collective memory is a representation of the past that is shared by members of a group such as a generation or nation-state. The concept can be traced to figures from the early twentieth century such as the sociologist Maurice Halbwachs and Frederic Bartlett, but it has recently emerged as part of the "memory boom" in the social sciences and humanities. The psychological dimensions of collective memory have recently been the focus of a growing body of research in the past few years (e.g., these were examined at a conference sponsored by the Luce Foundation at Washington University in 2006, and the topic is the focus of growing interdisciplinary research.

The study of individual memory, in contrast, focuses on the cognitive processes involved in the encoding, storage and retrieval of information in any one person. The study of these various aspects of memory has long been a central focus of cognitive psychology. Work in this area focuses on the various systems involved in forming and storing memories of different types, and how these systems can break down. As more has been learned about memory disorders and deficits, the individual approach to memory has grown to include neurobiological approaches as well. In particular, researchers at Washington University consider the neurological and cognitive impairments involved in Alzheimer's Disease.

1. Collective memory

a. History of the concept

Bartlett, F. (1932). Remembering: A Study in Experimental and Social Psychology. New York: Cambridge University Press.

Bartlett's account of remembering is an early psychological investigation of the phenomenon of collective memory. In Chapter 10, Bartlett offers a theory of memory wherein he characterizes it as "an imaginative reconstruction, or construction, built out of the relation of our attitude toward a whole active mass of organized past reactions or experiences" rather than "the re-excitation of innumerable fixed, lifeless and fragmentary traces". Such reconstructions, he goes on to argue in Chapter 17, are based within the social psychology of the group. Also in this Chapter, Bartlett engages with C. G. Jung and his idea of the collective unconscious.

Halbwachs, M. (1950). The Collective Memory. Trans. Francis J. Ditter, Jr. and Vita Yazdi. Introduction by Marky Douglas. New York: Harper-Colophon Books. (NB: There is also a newer edition of this work: On Collective Memory, which is edited, translated, and introduced by Lewis A. Coser (1992) and published by The University of Chicago Press.)

Maurice Halbwachs was born in Reims in 1877 and later became one of the most important European sociologists working in the Durkheimian tradition between the World Wars. Halbwachs coined the term "collective memory" in a book by the same name, wherein he argued that the concept was not a given but a socially constructed notion. Moreover, Halbwachs argued that, while collective memory is indeed a phenomenon of sociological importance, it is always individuals who remember certain facts or experiences. In other words, there are as many collective memories as there are groups or institutions in society, and groups and institutions are always constituted by individuals. Halbwachs draws a crucial distinction between historical and autobiographical memory, which he thought may work to obviate the disciplinary differences between history and sociology. In short, for Halbwachs, the memory of a nation or society is always a reconstruction of the past based within the context of the present, which necessarily affects the selective perception of past histories.

b. Contemporary approaches to collective memory

Wertsch, J. (2002). Voices of Collective Remembering. New York: Cambridge University Press.

Wertsch's book on collective memory offers a general recommendation for the merger of various approaches to the study of memory, from psychology's cognitive approach and sociology's cultural approach. Wertsch similarly advocates a middle ground between thinking about collective memory as a truly collective experience that exists apart from individuals and thinking about collective memory as merely the result of an amalgamation of individuals. After surveying the broad range of ways in which the term 'collective memory' has been used, Wertsch then establishes his own a particular view, which states that cultural memory is grounded in a society's textual and narrative resources. In particular, Wertsch focuses on the way Russian collective memory has been shaped by the various factors involved in the transition from Soviet to post-Soviet Russia.

Schwartz, B. (1982). "The Social Context of Commemoration: A study in Collective Memory". Social Forces, 61, 374-97.

In this book, Schwartz responds to Halbwachs' "presentist" approach to historical understanding, wherein the past is always understood in direct relation to the needs and concerns of the present. Schwartz argues that the past is always understood in an alteration of persistence and change, continuity and novelty. Collective memory, for Schwartz, is both the cumulative historical understanding of past societies as well as the understanding of the past in terms of present needs and contexts. The perceived needs of a given society may cause it to rewrite the past according to those specific needs, but the tradition of past interpretation provides a necessary continuity to any particular rewriting that may occur.

Draaisma, D. (2000). Metaphors of Memory: A History of Ideas about the Mind. Cambridge: Cambridge University Press.

A wide-ranging history concerning the metaphors that have been used in understanding the mind. From the slate to the computer, from Freud to Gall to Turing, Draaisma examines the images that have been deployed to describe and explain memory and the role it plays in the larger functioning of the mind.

Butler, T., ed. (1990). Memory: History, Culture and the Mind. Oxford: Basil Blackwell Ltd.

This collection of essays, first given as lectures at Wolfson College, Oxford, offers a wide variety of topics on memory, its history as a concept, and contemporary issues of collective memory. See especially Chapter 5 by Peter Burke, "History as Social Memory", as well as Chapter 6 by Geoffrey A. Hosking, "Memory in a Totalitarian Society: The Case of the Soviet Union".

Hobsbawm, E., & Ranger, T. (1983). The Invention of Tradition. Cambridge: Cambridge University Press.

This is a collection of essays about the nature of tradition-formation in English culture. By examining how a "national culture" develops, these anthropologists and historians how various understandings of the past intersect and affect the formation of actual collective practices, which, in turn, shape and re-shape the memories of collective histories.

Boyer, P. (1992). Tradition as Truth and Communication. Cambridge: Cambridge University Press.

In this book, Boyer addresses the concept of tradition from the dual disciplines of social anthropology and cognitive psychology. Boyer understands tradition to be a type of social interaction that is the result of repeating certain communicative events, and this book focuses primarily on oral communication.

Schwarz, V. (1998). Bridge Across Broken Time: Chinese and Jewish Cultural Memory. New Haven: Yale University Press.

This book is a critical exploration of the intersections and differences of the ways in which cultural memory is formed and transmitted in two of the oldest continuous civilizations in the world.

2. Cognitive memory systems

a. Systems vs. Processes

Foster, J., & Jelicic, M. (1999). Memory: Systems, Process, or Function? Oxford: Oxford University Press.

Explication of the various cognitive memory systems first requires the assumption that memory is compartmentalized into systems. Although this view has been the predominant one in cognitive psychology for the last 40 years, it has not gone unchallenged. Instead of viewing human memory as a collection of independent systems, each with their own distinctive features – as the systems view does – many researchers have begun to argue for an understanding of memory as a single system, accessed differently through different levels of processing. This anthology presents several views on this debate by various researchers in the area. It concludes with an analysis of the current state of the debate, and the needed direction for future research on this topic.

b. Systems

Schacter, D., & Tulving, E. (1994). Memory Systems, 1994. Cambridge, MA: MIT Press.

Schacter and Tulving, two prominent memory psychologists and advocates of the systems view, provide an encyclopedic overview of the memory systems found in humans and other animals. They use information cognitive psychology, neuropsychology, and neuroscience to distinguish the different behavioral components of memory and the neural systems that underlie them. They identify five major memory systems: working memory, semantic memory, episodice memory, perceptual representation, and procedural memory. Further, the authors criticize the process view of memory, arguing that the definition of "process" is hopelessly under-described by process theorists, leaving no coherent notion on which to delineate various aspects of memory.

Schacter, D., Wagner, A., & Buckner, R. (2000). "The memory systems of 1999." In E. Tulving & F. Craik (Eds.) The Oxford Handbook of Memory. New York: Oxford University Press.

The researchers in this article reconsider the five major memory systems advocated by Schacter and Tulving (1994) in light of recent neuroimaging research. They review the prominent methods used to delineate memory systems in 1994, and show how more recent imaging techniques provide further converging evidence for distinct memory systems.

c. Processes

Roediger, H. (1984). "Does current evidence from dissociation experiments favor the episodic/semantic distinction?" Behavioral and Brain Sciences, 7, 252-254.

In this article, Roediger claims that the methods used for delineating memory systems are not strong enough to warrant the desired conclusions. In particular Roediger argues that the dissociation evidence is not strong enough to provide support for a distinction between episodic and semantic memory systems. Memory for an event depends on the degree of similarity between the situations of encoding and retrieval, not the storage of the event in a particular system. Roediger argues for an alternative understanding of memory as a general processing ability, that leads to differences in behavioral outcomes when the information being encoded or retrieved is processed at a particular level.

Roediger, H., & Blaxton, T. (1987). "Retrieval modes produce dissociations in memory for surface information." In D. Gorfein & R. Hoffman (Eds.) Memory and Learning: The Ebbinghaus Centennial Conference, Hillsdale, NJ: Lawrence Erlbaum Associates, Publishers, pp. 349-379.

Roediger and Blaxton discuss the performance of amensics on various memory tasks, and evaluate the use of this evidence to support a distinction between semantic and episodic memory. They conclude that amnesiac performance is best viewed as spreading over a continuum of processing, with some deficits effecting more data-driven processing and others effecting more conceptually-driven processing. The reason there seems to be a dissociation between semantic and episodic memory systems is that episodic tasks are typically conceptually-driven, whereas semantic tasks are data-driven (Roediger and Blaxton, 1987).

d. Short-term memory vs. Long-term memory

Miller, G. (1956). "The magical number seven, plus or minus two: Some limits on our capacity for processing information." Psychological Review, 63, 81-97.

Miller was one of the first to examine and establish the limits of short-term processing in the human brain. His research shows that the average person is limited in the amount of information that can be processed and recalled at any one time. He stated that the average person can, at any one time, encode and recall seven bits of information, plus or minus 2. But by using the technique of chunking (organizing items into familiar, manageable units), more information can be included in each of the seven bits, allowing a person to extend their short-term memory capacity.

Atkinson, R., & Shiffrin, R. (1968). "Human memory: A proposed system and its control processes." In K. Spence (Ed.), The Psychology of Learning and Motivation: Advances in Research and Theory, Vol. 2. New York: Academic Press, pp. 89-195.

In this article, Atkinson and Shiffrin offer a three-stage processing model of human memory, which has shaped understanding of memory processes to this day. The three stages are sensory, short-term, and long-term memory. During the sensory memory stage, sensory input from the external environment is held briefly. Some of this information – what is deemed novel or important to attend to – is then encoded into short-term memory where it can be kept for a few minutes. Information that is particularly important is then further encoded so that it can reach long-term memory, where it can stay for days, months, or even years.

Brown, J. (1958). "Some tests of the decay theory of immediate memory." Quarterly Journal of Experimental Psychology, 10, 12-21.

Peterson, L. & Peterson, M. (1959). "Short-term retention of individual verbal items." Journal of Experimental Psychology, 58, 193-198.

Both Brown and Peterson & Peterson studied the rate of decay in short-term memory. The procedure by which they investigated short-term memory has come to be known as the Brown-Peterson task. In this procedure, a list of items is presented to the subject. Then, before recall, the subject is asked to spend time engaging in another task, such as subtracting by 3s from some large number. This is done to prevent rehearsal of the information presented earlier. Results from both of these studies show that recall drops dramatically as time for rehearsal is prohibited.

Muter, P. (1980). "Very rapid forgetting." Memory & Cognition, 8, 174-179.

Muter studied the rate of forgetting in short-term memory by having undergraduates learn and recall lists of items. However, unlike previous studies of recall memory, which tested subjects after each trial of learning a list of items, Muter only tested the subjects on one out of every 30 trials. He found that when he did so, rates of recall dropped dramatically. He thus concludes that previous estimates of the rate of forgetting in short-term memory significantly underestimate the rate by which information is lost.

e. Working memory

Baddeley, A., Hitch, G. (1974). "Working memory." In G. Bower (Ed.), The Psychology of Learning and Motivation: Advances in Research and Theory, Vol. 8, New York: Academic Press (pp. 47-89).

In this article, Baddeley and Hitch introduced a model of working memory. This view of working memory has multiple components: the central executive of working memory has two "slave systems" that are responsible for short-term precategorical storage of information. The first slave system, the phonological loop, stores auditory information, particularly the sounds of language. The second system, the visuospatial sketchpad, stores visual information. Both of these stores are supposed to be precategorical, holding information without processing meaning. Meaning is only integrated once the information is processed by the central executive.

Baddeley, A. (1992). "Working memory." Science, 255, 556-559.

Here Baddeley further expounds on the idea of working memory as it has evolved over the two decades since its inception. He argues for an understanding of working memory as a system dedicated to the temporary maintenance and manipulation of information. Further, he claims that such a system is a requisite first stage in the further comprehension and manipulation of information involved in higher-level cognitive activities.

Eriksen, C. & Collins, J. (1967). "Some temporal characteristics of visual pattern perception." Journal of Experimental Psychology, 74, 476-484.

Eriksen and Collins provide evidence that there is precategorical iconic memory – the ability to store visual information without processing meaning. This evidence was used to support the existence of a visuospatial sketchpad in Baddeley and Hitch's proposal of working memory. Eriksen and Collins showed that people were capable of holding random dot patterns in memory briefly such that the patterns could be combined to reveal meaningful dot patterns.

Crowder, R. & Morton, J. (1969). "Precategorical acoustic storage." Perception and Psychophysics, 5, 365-373.

Crowder and Morton showed that speech information could be held – briefly – in memory without the meaning of the information being processed. The possibility of phonological information being held precategorically was used to defend the existence of a phonological loop as a slave system to the central executive of working memory. Previous research had shown that we have the ability to hold onto auditory speech information, extending the time the information is available so that it can be encoded. What Crowder and Morton showed was that such information could be held in acoustic memory, even if it was meaningless. Thus nonwords (like "snoke") were held onto at the same rate as actual words.

Baddeley, A. & Wilson, B. (2002). "Prose recall and amnesia: Implications for the structure of working memory." Neuropsychologica, 40, 1737-1743.

In this article, Baddeley and Wilson argue for a new component of working memory: the episodic buffer. The episodic buffer provides temporary storage of one's current experience (held in a 'multimodal code') such that is capable of being combined with information from long-term memory to create an episodic memory. Their proposal is based on evidence from amnesics who show impaired performance in the formulation of episodic memories due to impairments in executive capacities.

f. Procedural vs. Declarative

Cohen, N. (1984). "Preserved learning capacity in amnesia: Evidence for multiple memory systems." In L. Squire & N. Butters (Eds.), Neuropsychology of Memory, New York: Guillford Press, pp. 83-103.

Cohen's work with amnestics shows that patients with retrograde amnesia for past events can still perform well on skills they learned prior to their accident. This was done by teaching patients certain skills – like reading words backwards in a mirror – prior to their receiving ECT. In fact, patients with retrograde amnesia were able to learn the task just as well as those without it, even though the amnestics had no ability to recall the particular words on which they had been tested previously. Cohen concludes that this supports a difference between procedural and declarative memory, because amnesia can differentially affect the two systems.

Tulving, E. (1985). "How many memory systems are there?" American Psychologist, 40, 385-398.

Tulving offers a distinction between three memory systems: procedural memory, and two forms of declarative memory: semantic and episodic. Procedural memory, as he defines it, involves learning behavioral responses to particular environmental stimuli. It does not require conscious awareness. Tulving goes on to discuss the various methodological ways in which procedural memory can be distinguished from other memory systems.

Squire, L. & Zola-Morgan, S. (1991). "The medial temporal lobe memory system." Science, 253, 1380-1386.

Squire and Zola-Morgan argue that the category of procedural memory should be further subdivided into component memory systems. Their claims are based on studies of the areas of the brain involved in the impairments seen in human amnestics and animal models.

g. Episodic vs. Semantic

Tulving, E. (1972). "Episodic and semantic memory." In E. Tulving & W. Donaldson (Eds.), Organization of Memory, New York: Academic Press (pp. 381-403).

It is here that Tulving first proposed a distinction between episodic and semantic memory. Episodic memory is generally described as the storage and recollection of personally-relevant events and experiences, whereas semantic memory is described as the storage and recollection of general facts about the world. For example, knowing that one's childhood dog was named 'Zippy' would be a recollection from episodic memory; being able to list several breeds of dog would be a recollection from semantic memory.

Tulving, E. (1983). Elements of Episodic Memory. New York: Oxford University Press.

A decade after proposing the existence of episodic memory, Tulving concluded that there was enough evidence accumulated for him to make the additional claim that episodic and semantic memory represented two functionally separable memory systems. In support of this claim Tulving cites evidence from Shoben, Wescourt and Smith (1978) and Jacoby and Dallas (1981), among others, showing that semantic and episodic memory performance can be dissociated from one another. In the Shoben et al. paper, for example, it was found that subjects' performance on semantic verification of sentences was influenced by relatedness, but not fanning, whereas their performance on episodic recognition showed the opposite trend.

McKoon, G., Ratcliff, R., & Dell, G.S. (1986). "A critical evaluation of the semantic-episodic distinction." Journal of Experimental Psychology: Learning, Memory, and Cognition, 12, 295-306.

McKoon, Ratcliff, and Dell challenge whether Tulving's episodic memory constructs are empirically testable, and argue that many of the distinctions Tulving proposed were not defined clearly enough to be testable by empirical methods. And further, they claim that even those that are potentially testable present a host of difficulties for Tulving's view. For example, Tulving has claimed that episodic memories are more vulnerable to forgetting, but Ratcliff et al. point out that it is difficult to control for learning and material difficulty across these two types of memory so as to adequately test this proposal.

Neely, H. (1989). "Experimental dissociations and the episodic/semantic memory distinction." In H. Roediger & F. Craik (Eds.) Varieties of Memory and Consciousness: Essays in Honor of Endel Tulving. Hillsdale, N.J.: Lawrence Erlbaum Associates, Publishers (pp. 229-270).

Neely provides an overview of the methods and results that have been used to support the distinction between episodic and semantic memory. In particular, Neely focuses on research from nonamnesic subjects, and experiments from his own laboratory. He shows how these results support Tulving's general claim, while challenging some of his particular views about the nature of each memory system.

Baddeley, A., Aggleton, J., & Conway, M., (Eds). (2002). Episodic Memory: New Directions in Research. New York: Oxford University Press.

Baddeley, Aggleton and Conway are the editors for a book on the topic of episodic memory, centered around the following questions: How are episodic memories stored in the brain? Why do certain memories disappear but not others? What causes false memories? Additionally, the articles in the book explore questions as to the nature of episodic memory, how it should be studied, and whether it is an exclusively human ability (as Tulving once claimed).

h. Levels of Processing

Craik, F. & Lockheart, R. (1972). "Levels of processing: A framework for memory research." Journal of Verbal Learning & Verbal Behavior, 11, 671-684.

In this article, Craik and Lockheart challenged the dual-store model of memory, a view which states that the characteristics of any particular memory are a function of where that memory is stored. For example, items in short-term memory are more susceptible to loss than items in long-term memory, not because of their content, but because of their location. As an alternative, Craik and Lockheart proposed that it was the level of processing of a memory item that determined its characteristics. Further, they claimed that differences in processing were not categorical, but rather existed on a continuum from shallow to deep processing. Shallow processing only leaves weak memory traces, and is thus susceptible to rapid decay. Deeper processing results in memories that are longer-lasting and less susceptible to decay and interference.

Craik, F. & Tulving, E. (1975). "Depth of processing and the retention of words in episodic memory." Journal of Experimental Psychology: General, 104, 268-294.

This article presents 10 experiments testing the levels of processing view of human memory, as first proposed by Craik and Lockhart. Subjects were given lists of words and asked to answer questions concerning the physical, phonemic or semantic characteristics of the words included. later, subjects were surprised with recall tests. The experiments confirmed the levels of processing view, by showing that words associated with deeper (semantic) questions were retained at a higher rate than those that had not received the same processing. The researchers describe their results in terms of the degree of elaboration of a memory trace. Traces which receive deeper processing, or more elaboration, lead to greater retention.

Morris, C., Bransford, J., & Franks, J. (1977). "Levels of processing versus transfer appropriate processing." Journal of Verbal Learning & Verbal Behavior, 16, 519-533.

Morris et al. offer a refinement of the conclusion that semantic, or deep, processing is the best way of elaborating a memory trace for further retention. As they point out, the results of previous studies are biased because the semantic elaboration tasks bear the closest resemblance to the requirements of recall. They suggest that it is not that deep elaboration is the best, but rather that memory benefits from the study of features of a trace that will be emphasized in recall. That is, it is best to pay attention to the characteristics of information that you will be asked to retain.

3. Neurobiological approach to memory

a. Animal models

Clayton, N.S., & Dickinson, A.D. (1998). "Episodic-like memory during cache recovery by scrub jays." Nature, 395, 272-274.

In studies with scrub jays, Clayton and Dickinson show evidence of behavior indicative of episodic memories. Scrub jays are able to store and recover their food from visuospatially distinct areas. The birds appear to be representing information about the spatial and temporal properties of their food-caching experiences. They are capable of representing the location of the food even after long periods of time and when cues in the environment have been changed. This challenges Tulving's basic idea that episodic memory quires a concept of the self, and is thus only available to humans.

Morris, R. (2002). "Episodic-like memory in animals: psychological criteria, neural mechanisms, and the value of episodic-like tasks to investigate animal models of neurodegenerative disease." In A. Baddeley, J. Aggleton, M. & Conway, (Eds.), Episodic Memory: New Directions in Research. New York: Oxford University Press. (pp.181-203).

Morris challenges Tulving's (1983) idea that episodic memory can only exist in humans by presenting evidence that certain mammals posses at least an 'episodic-like' memory system. Seeing the possibility of episodic memory in animals requires abandoning the one-trial learning tasks in favor of tasks that look at animal memory more extensively.

b. Long-term Potentiation

Hawkins, R., Clark, G., & Kandel, E. (1987). "Cell biological studies of learning in simple vertebrate and invertebrate systems." In F. Plum (ed) Handbook of Physiology, Section 1: The Nervous System, Bethesda, MD: American Psychological Society. (pp. 25-83).

Aplysia (small marine snails) posses a basic reflex to withdraw their gill and siphon (a tube-like sphincter) upon external stimulation as a defense mechanism. In this and other studies Hawkins et al. have shown that this reflex can be sensitized such that it occurs in accordance with associative learning. This sensitization learning can even be made to last for days or weeks. This is made possible through the Long Term Potentiation (LTP) of the interconnected neurons in these creatures. Stated briefly, LTP is a change to a neuron that occurs after repeated communicative contact with another neuron. These learning traces are speculated to be the biological substrate of memory formation.

Clark, G., & Schuman, E. (1992). "Snails' tales: Initial comparisons of synaptic plasticity underlying learning in Hermissenda and Aplysia." In L. Squire and N. Butters (eds) Neuropsychology of Memory, 2nd ed., New York: Guilford Press (pp. 602).

In this review article Clark & Schuman detail research into the molecular processes underlying learning and memory as they have been studied in the invertebrates Aplysia and Hermissenda. They discuss the mechanisms by which synaptic facilitation occurs in these organisms, and how fundamental principles of these mechanisms can illuminate the nature of learning and memory more generally.

Terje, L. (2003). "The discovery of long-term potentiation". Philosophical Transactions of the Royal Society of London: Biological Sciences B, 358, 617-20.

Terje was one of the initial discoverers of the phenomenon of long-term potentiation. In this paper, Terje describes the circumstances surrounding the discovery of LTP, and work with Anderson and Bliss in the late 1960s. He discusses the original findings regarding the significance of LTP, and how they have been extended and modified by more recent work on the molecular mechanisms of memory.

Squire, L. (1992). "Memory and the hippocampus: A synthesis from findings with rats, monkeys, and humans." Psychological Review, 99, 195-231.

In this study Squire examines the role of the hippocampus in memory function, amalgamating findings from a variety of studies of rats, monkeys and humans. He shows that across these distinct literatures a similar picture of the role of the hippocampus in memory processing has been established. Squire claims that the hippocampus plays a distinct role in the formation of declarative or explicit memories. Nondeclarative or implicit memories, in contrast, do not involve the hippocampus. Squire further speculates that the importance of the hippocampus for declarative memory formation stems from its ability to integrate and syntesize information from various parts of the cortex.

Morris, R., Anderson, E., Lynch, G., & Baudry, M. (1986). "Selective impairment of learning and blockade of long-term potentiation by an N-methyl-D-aspartate receptor antagonist, AP5". Nature, 319, 774-6.

In this study, Morris et al. provided one of the first indications of the importance of long-term potentiation (LTP) for the formation of memories. These experiments tested the spatial memory of rats by teaching them to navigate a water maze both before and after modifications to the hippocampus. Due to the popularity of the technique, the task has come to be known as the "Morris water maze." This study showed that removal of NMDA receptors (thereby blocking the ability for LTP in neurons with these receptors) inhibited rats from learning to navigate the maze in comparison to controls.

Bliss, T., Collingridge, G., & Laroche, S. (2006). "Neuroscience: ZAP and ZIP, a story to forget". Science, 313: 1058-9.

In further studies of the role of LTP in memory, Bliss et al. show that the strengthening of synaptic connections that comes from LTP is responsible not only for the formation of new memories, but also of forgetting irrelevant or old information. These findings further solidify the importance of LTP as the neural substrate of memory.

c. Neural correlates of memory

Wagner, D., Schacter, D., Rotte, M., Koutstaal, W., Maril, A., Anders, A., Rosen, B., & Buckner, R. (1998). "Building memories: Remembering and forgetting of verbal experiences as predicted by brain activity." Science, 281, 1188-1191.

Wagner et al.'s study of the nature of remembering used brain activity during the encoding of words to predict later remembering. Subjects saw a list of words and made judgments on them (abstract vs. concrete). Later, the subjects were presented with a set of words – half of which were from the original presentation; the other half were knew. The researchers found that there were two regions of the brain (the parahippocampal gyrus and an area of the frontal lobe) that showed greater activity for the old words that subjects were later able to recognize as part of the list. The study was remarkable because it showed the possibility that memory performance could be predicted from how the original trace was encoded.

Squire, L. (1997). "Memory systems of the brain." Brain and Cognition, 35, 297-298.

In this article, Squire reviews the ideas about memory, its nature and how it should be tested across the last half of the 20th century. He details early views of various dichotomies between types of memory – based largely on work from amnestic patients – to more contemporary approaches that seek to ground aspects of memory in various brain regions. Squire concludes with discussion of the current views as to how the brain systems of memory function and give rise to behavior in humans and other intelligent species.

McClelland, J., McNaughton, B., & O'Reilly, R. (1995). Why there are complementary learning systems in the hippocampus and neocortex: Insights from the success and failures of connectionist models of learning and memory, Psychological Review, 102, 419-457.

Damage to the hippocampus tends to disrupt recent memories while leaving more distant memories intact. Here McClelland et al present an account of memory storage that accounts for this phenomenon. They suggest that memories are first stored in the hippocampal system, and are later based on changes in neocortical areas. From this model, the researchers draw conclusions about the memory functions of each system. The neorcortex learns slowly, gradually incorporating new information with pre-existing memory stores. The hippocampus, in contrast, rapidly acquires new information, and holds it until it can be integrated into the neocortical system.

Vargha-Khadem, F., Gadian, D.G., Watkins, K.E., Connely, A, Van Paesschen, W., & Mishkin, M. (1997). Differential effects of early hippocampal pathology on episodic and semantic memory. Science, 277, 376-380.

Vargha-Khadem et al. have shown that some young children who experience prenatal strokes have diminished episodic recollection, despite possessing normal intelligence and semantic abilities. Further, Vargha-Khadem has shown that their brain damage is restricted to a bilateral portion of the hippocampus, suggesting that this is an area of the brain exclusively involved in episodic memory. This has led Tulving to redefine the relation between episodic and semantic memory.

Tulving, E., & Markowitsch, H.J. (1998). Episodic and declarative memory: Role of the hippocampus, Hippocampus, 8, 198-204.

In this article, Tulving and Markowitsch refine the claim about the nature of episodic memory in light of Vargha-Khadem et al.'s findings. Here they claim that semantic and episodic memory share a host of features: they both involve representational information, stored propositionally that has a truth-value. The overlap of these features demarcates the realm of declarative memory, which we share with animals, while the truly episodic features (those missing in the patients studied by Vargha-Khadem) are exclusively human and underwritten by specific brain areas.

4. Memory Disorders

a. Amnesias

Milner, B. (1959). "The memory defect in bilateral hippocampal lesions." Psychiatric Research Reports, 11. Scovile, W. & Milner, B. (1957). "Loss of recent memory after bilateral hippocampal lesions." Journal of Neurological and Neurosurgical Psychiatry, 20, 11-12.

These two articles present the case of the patient H.M., the study of whose memory deficits has had a significant impact on our contemporary understanding of the nature of memory. H.M. had the two lobes of his hippocampus severed as part of a surgery to alleviate chronic epileptic seizures. The surgery was successful at preventing the seizures, but it left H.M. with a disastrous side effect: he lost the ability to form new memories. His anterrograde amnesia was restricted to declarative knowledge; he retained the ability to engage in procedural learning. His case provided support for a dissociation between short and long term memory, and between explicit and implicit memory.

Shallice, T. & Warrington, E. (1970). "Independent functioning of verbal memory stores: A neuropsychological study Quarterly Journal of Experimental Psychology, 22, 261-273.

In this article, Shallice and Warrington present the case of K.F. K.F. was a patient who suffered from Korsakoff's syndrome, and displayed a variety of problems with short-term memory. He showed faster forgetting of auditory information thatn visual information. In particular, he showed rapid decay of speech related auditory information. K.F.'s case is important because it shows an opposite pattern of deficit from H.M., as K.F. shows intact long-term memory, but impaired short-term memory.

Tulving, E. (2002). "Episodic memory: from mind to brain." Annual Reviews of Psychology, 53, 1-25.

In this article, Tulving discusses K.C., an amnestic patient that has been studied because of his deficits in epidosic memory. As Tulving describes, K.C. performs many cognitive tasks normally, but shows little to no recollection of personal life events. Besides experiencing the current moment, K.C. seems to have no conception of subjective time, thereby showing deficit in what Tulving takes to be one of the key components of episodic memory (autonoetic consciousness).

Taylor, K., Henson, R., & Graham, K. (2007). Recognition memory for faces and scenes in amnesia: Dissociable roles of medial temporal lobe structures. Neuropsychologia Vol 45, 2428-2438

In this article Taylor et al. explore an alternative explanation of the role of the hippocampus and perirhinal cortex in recognition memory. Their conclusions are based on the perceptual deficits of amnesics with medial temporal lobe lesions. Previous work has suggested that the hippocampus and perirhinal cortex might play a similar role in recognition memory, wheares the researchers here show that their respective roles can be distinguished according to the type of material to be remembered.

Hartley, T., Bird, C., Chan, D., Cipolotti, L., Husain, M., Vargha-Khadem, F., & Burgess, N. (2007). The Hippocampus Is Required for Short-Term Topographical Memory in Humans. Hippocampus Vol 17(1) (2007): 34-48

The hippocampus plays a crucial role within the neural systems for long-term memory, but little if any role in short-term memory. Here the researchers explored the idea that the hippocampus may play an indirect role in short-term memory, by processing allocentric topographical information, which impacts perception and short-term memory. This possibility was examined through experiments with four patients who suffer from focal hippocampal damage. Topographical perception in the tasks was found to be related to the degree of hippocampal damage across patients. The researchers thus conclude that the hippocampus supports allocentric topographical processing, thereby playing an indirect role in short-term memory processing.

b. Aging & Alzheimer's

Balota, D., & Duchek, J. (1991). Semantic priming effects, lexical repetition effects, and contextual disambiguation effects in healthy aged individuals and individuals with senile dementia of the Alzheimer type, Brain and Language, 40, 181-201.

Balota and Duchek examined differences in visual word recognition across healthy-aged and Alzheimer's patients. They found stronger semantic priming and lexical repetition effects for subjects with Alzheimer's than healthy-aged subjects. They discuss the role of attention in modulating performance across groups.

Balota, D.A., Cortese, M.J., Duchek, J.M., Adams, D., Roediger, H.L., McDermott, K.B., & Yerys, B.E. (1999). Veridical and false memories in healthy older adults and in dementia of the Alzheimer's Type. Cognitive Neuropsychology, 16, 361-384.

Balota et al. explored the relation between veridical and false memories across age groups and cognitive impairment. Five groups of participants (young, healthy old, healthy old-old, very mild dementia of the Alzheimer's type, and mild DAT) studied and were tested on 6 12-item lists of words selected from the Deese-Roediger-McDermott (DRM) paradigm. Both veridical recall and recognition performance decreased as a function of age of the participants and as a function of dementia severity. However, the recall and recognition of the highly related nonpresented items actually increased as a function of age, and only slightly decreased as a function of dementia of the Alzheimer's type. When false memory was considered as a proportion of veridical memory, there was a clear increase as a function of both age of the participants and as a function of disease severity.

Faust, M.E., Balota, D.A., & Spieler, D.H. (2001). Building episodic connections:Changes in episodic priming with age and dementia. Neuropsychology, 15, 626-637.

Previous studies of associative encoding that used explicit retrieval tasks have shown both age- and Alzheimer's-related declines, but such results may be biased by group differences in explicit retrieval. In the present experiment, the authors assessed implicit associative encoding for youner and older healthy adults and older adults with dementia of the Alzheimer's type during a speeded word-naming task using an episodic priming measure. Episodic priming refers to the facilitation in responding to a target word after repetition of both words in a prime-target pair, in comparison with simple repetition of the target word with a new prime on each presentation. In contrast with other studies of implicit associative encoding that did not use an implicit episodic priming measure, the present study found both age- and Alzheimer's-related declines in associative encoding under conditions of massed learning trials.

Watson, J.M., McDermott, K.B., & Balota, D.A. (2004). Attempting to avoid false memories in the Deese/Roediger-McDermott paradigm: Assessing the combined influence of practice and warnings in young and old adults. Memory & Cognition,32, 135-141.

In this study, Watson et al. studied the impact of warning subjects about the possibility of false memories in the DRM paradigm across older and younger adults. Young and old adults attempted to memorize the same list of 60 words. Half of the participants in each age group were given an explicit warning about the potential for false memory formation in the DRM paradigm prior to encoding and were asked to attempt to avoid recalling any associated but nonpresented words. Lists were presented at either a fast or a slow rate. When a warning about false recall was provided, young adults virtually eliminated false recall by the second trial. Even though old adults also used warnings to reduce false recall on Trial 1, they were still unable to decrease false memories across the remaining trials. Old adults also reduced false recall more with slow than with fast presentation rates. These findings suggest that old adults have a breakdown in spontaneous, self-initiated source monitoring as reflected by little change in false recall across study-test trials but a preserved ability to use experimenter-provided warnings or slow presentation rates to reduce false memories.

5. Errors & Forgetting

Roediger, H. (1996). "Memory illusions." Journal of Memory and Language, 35, 76-100.

In this article, Roediger makes an analogy between visual illusions and their role in explaining the nature of vision and memory illusions and their role in explaining the nature of memory. Roediger defines memory illusions as cases when a person's report of a past event deviates from what actually happened. He then goes on to sketch a history of how memory illusions have been studied, with an emphasis on contemporary approaches to memory illusions in cognitive psychology.

a. Misattribution

Roediger, H. & McDermott, K. (1995). "Creating false memories: Remembering words not presented in lists." Journal of Experimental Psychology: Learning, Memory & Cognition, 21, 803-814.

Two experiments (modeled after J. Deese's 1959 study) revealed remarkable levels of false recall and false recognition in a list learning paradigm. When given a list of associated words, subjects often recalled (in free recall) an associated, but non represented word. In fact, recall for the associated word was at a rate comparable to the recollection of any of the words actually presented in the original list. The results reveal a powerful illusion of memory: People can remember events that never happened. This paradigm has come to be known as the DRM paradigm, and exploration of this paradigm has played an influential role in the contemporary study of memory for the last decade.

McDermott, K. & Roediger, H. (1998). "Attempting to avoid illusory memories: Robust false recognition of associates persists under conditions of explicit warnings and immediate testing." Journal of Memory and Language, 39, 508-520.

Given their previous findings that associated words can induce false memories, the experiments in this article were designed to test the strength of the effect. In recall, when subjects where asked to distinguish between whether they remembered a particular item being on the original list or merely knew that it had been in the set, subjects reported remembering the associated but non represented items at the same rate as represented items. Further, when warned about the possibility of making false memory judgments, performance improved but there was still a false recognition effect. The researchers conclude that this memory illusion is remarkably robust and little affected by the instructional manipulations.

Neisser, U. & Harsch, N. (1992). "Phantom flashbulbs: False recollections of hearing the news about Challenger." In E. Winograd and U. Neisser (Eds) Affect and Accuracy in Recall: Studies of Flashbulb Memories. Cambridge: Cambridge University Press.

In this study, undergraduate students were given a questionnaire the day after the Challenger (A NASA shuttle headed for space) exploded upon takeoff. The questionnaire asked them what they were doing at the time, etc. The students were then given the same questionnaire two years later. Results showed that memory was only accurate on 25% of the questions. However, students reported strong confidence in their recollections after the two-year interval. Thus, the study shows that confidence and veracity are not necessarily related in memory. Further, the study shows that memory is not veridical, but constructive. Each time we revisit an event we lay down a new trace, which is integrated with the original trace.

Marsh, E.J. (in press). "Retelling is not the same as recalling: Implications for memory." Current Directions in Psychological Science.

In this article, Marsh discusses the differences between recalling, as often required in laboratory settings, and the sorts of retellings people do when speaking to others about their life experiences. Retellings are often less accurate, and place more emphasis on the speaker's goals and the conversational context in which the speaker finds him or herself. As Marsh explains, these retellings have an impact on memory. The selective rehearsal (where certain facts are emphasized, elaborated, or exaggerated) contributes to the later memory of that event. In this way, retellings cause memory errors similar to those witnessed in cases of false flashbulb memories.

b. Suggestibility: Loftus and Jacoby

Loftus, E., Miller, D., & Burns, H. (1978). "Semantic integration of verbal information into a visual memory." Journal of Experimental Psychology: Human Learning & Memory, 4, 19-31.

In this study, Loftus et al. had undergraduates watch a series of slides depicting an auto accident. Following the slides, subjects were given either consistent, misleading, or irrelevant information about the event to see what, if any, effect information given after an event has on a witness's memory. Results show that misleading information produced less accurate responding on a questionnaire about the event. Overall results suggest that information to which a witness is exposed after an event, whether that information is consistent or misleading, is integrated into the witness's memory of the event.

Jacoby, L., Woloshyn, V., & Kelley, C. (1989). "Becoming famous without being recognized: Unconscious influences of memory produced by dividing attention." Journal of Experimental Psychology: General, 118, 115-125.

Jacoby et al.'s study shows that people can often misinterpret feelings of familiarity and that this phenomenon can create false memories. Specifically, the study shows that the familiarity of names – brought about by their prior presentation – can be misattributed as fame. In this study, subjects were presented with a list of famous and nonfamous under conditions of full or divided attention. Divided attention greatly reduced later recognition memory performance but had no effect on gains in familiarity (as measured through fame judgments). In later experiments, subjects read a list of only nonfamous names, again under either a full or divided attention condition. When subjects studied the list with full attention, recognition was high and the subjects did not often mistake their familiarity with a name for the famousness of the person. However, subjects in the divided attention condition had reduced recognition of names from the prior list and were more likely to mistake names from the list for famous ones. The researchers conclude that conscious recollection is an attention-demanding act that is separate from assessing familiarity.

c. Transience/Interference:

Waugh, C. & Norman, A. (1965). "Primary memory." Psychological Review Vol 72(2) (Mar 1965): 89-104.

In this paper, Waugh and Norman evaluate different ways in which short-term memory can be understood. At the time, it was commonly known that information in short-term memory rapidly decayed. What was a matter of dispute was whether this decay was due to time elapsing or due to interference from new information. Waugh and Normal designed a study, using a probed-recall task, to show that interference – and not transience – is the cause of forgetting from short-term memory. Subjects were presented with a list of numbers at a fast or slow rate, and then asked to recall the digit that followed a pre-specified probe digit. If transience theory were right, the amount of forgetting should increase as the digits were read at a slower rate. However, the results of the study showed that forgetting only increased as a function of the number of digits between the probe and recall, suggesting that forgetting is a phenomenon that happens because of an increase in information, regardless of the retention interval.

Anderson, M., & Neely, J. (1996). "Interference and inhibition in memory retrieval." In E. Bjork & R. Bjork (eds) Memory. San Diego: Academic Press.

In this article, Anderson and Neely review the breadth of experimental work in cognitive psychology, as it pertains to the causes of memory interference. They review the classical interference paradigms, and more recent evidence that challenges these traditional views. Further, the authors discuss the relation between memory interference and other cognitive phenomena; namely, selective attention and retrieval from semantic and episodic memory.