Collective memory refers to the shared pool of memories, knowledge and information of a social group that is significantly associated with the group's identity. The English phrase "collective memory" and the equivalent French phrase "la mémoire collective" appeared in the second half of the nineteenth century. The philosopher and sociologist Maurice Halbwachs analyzed and advanced the concept of the collective memory in the book La mémoire collective (1950).
 Collective memory can be constructed, shared, and passed on by large 
and small social groups. Examples of these groups can include nations, 
generations, communities among others. Collective memory has been a topic of interest and research across a number of disciplines, including psychology, sociology, history, philosophy and anthropology.
Conceptualization of collective memory
Attributes of collective memory
Collective
 memory has been conceptualized in several ways and proposed to have 
certain attributes. For instance, collective memory can refer to a 
shared body of knowledge (e.g., memory of a nation's past leaders or 
presidents);
 the image, narrative, values and ideas of a social group; or the 
continuous process by which collective memories of events change.
History versus collective memory
The
 difference between history and collective memory is best understood 
when comparing the aims and characteristics of each. A goal of history 
broadly is to provide a comprehensive, accurate, and unbiased portrayal 
of past events. This often includes the representation and comparison of
 multiple perspectives and the integration of these perspectives and 
details to provide a complete and accurate account. In contrast, 
collective memory focuses on a single perspective, for instance, the 
perspective of one social group, nation, or community. Consequently, 
collective memory represents past events as associated with the values, 
narratives and biases specific to that group.
Studies have found that people from different nations can have 
major differences in their recollections of the past. In one study where
 American and Russian students were instructed to recall significant 
events from World War II and these lists of events were compared, the 
majority of events recalled by the American and Russian students were 
not shared.
 Differences in the events recalled and emotional views towards the 
Civil War, World War II and the Iraq War have also been found in a study
 comparing collective memory between generations of Americans.
Perspectives on collective memory
The concept of collective memory, initially developed by Halbwachs, has been explored and expanded from various angles – a few of these are introduced below. 
James E. Young has introduced the notion of 'collected memory' 
(opposed to collective memory), marking memory's inherently fragmented, 
collected and individual character, while Jan Assmann
 develops the notion of 'communicative memory', a variety of collective 
memory based on everyday communication. This form of memory is similar 
to the exchanges in an oral culture or the memories collected (and made 
collective) through oral history. As another subform of collective 
memories Assmann mentions forms detached from the everyday, it can be 
particular materialized and fixed points as, e.g. texts and monuments.
The theory of collective memory was also discussed by former Hiroshima resident and atomic bomb survivor, Kiyoshi Tanimoto,
 in his tour of the United States as an attempt to rally support and 
funding for the reconstruction of his Memorial Methodist Church in 
Hiroshima. He theorized that the use of the atomic bomb had forever been
 added to the world's collective memory and would serve in the future as
 a warning against such devices.
The idea was also discussed more recently in The Celestine Prophecy and subsequent novels written by James Redfield
 as a continuing process leading to the eventual transcendence of this 
plane of existence. The idea that a futuristic development of the collective unconscious
 and collective memories of society allowing for a medium with which one
 can transcend ones existence is an idea expressed in certain variations
 of new age religions.
The historian Guy Beiner,
 an authority on memory and history on Ireland, has criticized  the 
unreflective use of the adjective "collective" in many studies of 
memory: 
The problem is with crude concepts of collectivity, which assume a homogeneity that is rarely, if ever, present, and maintain that, since memory is constructed, it is entirely subject to the manipulations of those invested in its maintenance, denying that there can be limits to the malleability of memory or to the extent to which artificial constructions of memory can be inculcated. In practice, the construction of a completely collective memory is at best an aspiration of politicians, which is never entirely fulfilled and is always subject to contestations.
 In its place, Beiner has promoted the term "social memory" and has also demonstrated its limitations by developing a related concept of "social forgetting".
Collective memory and psychological research
Though
 traditionally a topic studied in the humanities, collective memory has 
become an area of interest in psychology. Common approaches taken in 
psychology to study collective memory have included investigating the 
cognitive mechanisms involved in the formation and transmission of 
collective memory; and comparing the social representations of history 
between social groups.
Social representations of history
Research
 on collective memory have taken the approach to compare how different 
social groups form their own representations of history and how such 
collective memories can impact ideals, values, behaviors and vice versa.
  Developing social identity and evaluating the past in order to prevent
 past patterns of conflict and errors are proposed functions of why 
groups form social representations of history. This research has focused
 on surveying  different groups or comparing differences in 
recollections of historical events, such as the examples given earlier 
when comparing history and collective memory.
Differences in collective memories between social groups, such as
 nations or states, have been attributed to collective narcissism and 
egocentric/ethnocentric bias. In one related study where participants 
from 35 countries were questioned about their country's contribution to 
world history and provided a percentage estimation from 0% to 100%, 
evidence for collective narcissism was found as many countries gave 
responses exaggerating their country's contribution. In another study 
where American's from the 50 states were asked similar questions 
regarding their state's contribution to the history of the United 
States, patterns of overestimation and collective narcissism were also 
found.
Cognitive mechanisms underlying collaborative recall
Certain
 cognitive mechanisms involved during group recall and the interactions 
between these mechanisms have been suggested to contribute to the 
formation of collective memory. Below are some mechanisms involved 
during when groups of individuals recall collaboratively.
Collaborative inhibition and retrieval disruption
When
 groups collaborate to recall information, they experience collaborative
 inhibition, a decrease in performance compared to the pooled memory 
recall of an equal number of individuals. Weldon and Bellinger (1997) 
and Basden, Basden, Bryner, and Thomas (1997) provided evidence that 
retrieval interference underlies collaborative inhibition, as hearing 
other members' thoughts and discussion about the topic at hand 
interferes with one's own organization of thoughts and impairs memory. The main theoretical account for collaborative inhibition is retrieval disruption.
 During the encoding of information, individuals form their own 
idiosyncratic organization of the information. This organization is 
later used when trying to recall the information. In a group setting as 
members exchange information, the information recalled by group members 
disrupts the idiosyncratic organization one had developed. As each 
member's organization is disrupted, this results in the less information
 recalled by the group compared to the pooled recall of participants who
 had individually recalled (an equal number of participants as in the 
group).
Despite the problem of collaborative inhibition, working in 
groups may benefit an individual's memory in the long run, as group 
discussion exposes one to many different ideas over time. Working alone 
initially prior to collaboration seems to be the optimal way to increase
 memory. 
Early speculations about collaborative inhibition have included 
explanations, such as diminished personal accountability, social loafing
 and the diffusion of responsibility, however retrieval disruption 
remains the leading explanation. Studies have found that collective 
inhibition to sources other than social loafing, as offering a monetary 
incentive have been evidenced to fail to produce an increase in memory 
for groups.
 Further evidence from this study suggest something other than social 
loafing is at work, as reducing evaluation apprehension – the focus on 
one's performance amongst other people – assisted in individuals' 
memories but did not produce a gain in memory for groups. Personal 
accountability – drawing attention to one's own performance and 
contribution in a group – also did not reduce collaborative inhibition. 
Therefore, group members' motivation to overcome the interference of 
group recall cannot be achieved by several motivational factors.
Cross-cueing
Information
 exchange among group members often helps individuals to remember things
 that they would not have remembered had they been working alone. In 
other words, the information provided by Person A may 'cue' memories in 
Person B. This phenomenon results in enhanced recall.
Error pruning
Compared
 to recalling individually, group members can provide opportunities for 
error prune during recall to detect errors that would otherwise be 
uncorrected by an individual.
Social contagion errors
Group
 settings can also provide opportunities to exposure of erroneous 
information that may be mistaken to be correct or previously studied.
Re-exposure effects
Listening
 to group members recall the previously encoded information can enhance 
memory as it provides a second exposure opportunity to the information.
Forgetting
Studies
 have shown that information forgotten and excluded during group recall 
can promote the forgetting of related information compared to 
information unrelated to that which was excluded during group recall. 
Selective forgetting has been suggested to be a critical mechanism 
involved in the formation of collective memories and what details are 
ultimately included and excluded by group members. This mechanism has 
been studied using the socially shared retrieval induced forgetting paradigm, a variation of the retrieval induced forgetting method with individuals.
Synchronization of memories (from dyads to networks).
Bottom-up
 approaches to the formation of collective memories investigate how 
cognitive-level phenomena allow for people to synchronize their memories
 following conversational remembering. Due to the malleability of human 
memory, talking with one another about the past results in memory 
changes that increase the similarity between the interactional partners'
 memories. 
 When these dyadic interactions occur in a social network, one can 
understand how large communities converge on a similar memory of the 
past.
 Research on larger interactions show that collective memory in larger 
social networks can emerge due to cognitive mechanisms involved in small
 group interactions.
Collective memory, culture and the public sphere
Memorialization of collective memory
The
 collective memory of a nation is represented in part by the memorials 
it chooses to erect. Public memory is enshrined in memorials from the Holocaust memorial in Berlin to the Vietnam Veterans Memorial
 in Washington, DC. Whatever a nation chooses to memorialize in physical
 monument, or perhaps more significantly, what not to memorialize, is an
 indicator of the collective memory.
Collective memory is also sustained through a continuous 
production of representational forms. In the media age – and maybe 
particularly during the last decade of increasing digitization
 – this generates a flow of, and production of, second hand memories 
(see James E. Young below). Particular narratives and images are 
reproduced and reframed, yet also questioned and contested through new 
images and so forth. Collective memory today differs much from the 
collective memories of an oral culture, where no printing technique or 
transportation contributed to the production of imagined communities
 in which people come to share a sense of heritage and commonality with 
many human beings we have never met – as in the manner a citizen may 
feel a sort of 'kinship' with people of the same nation, region or city.
Mass media and collective memory
Film and television
The arrival of film
 created many images, film scenes, news scenes, photographs, quotes, and
 songs, which became very familiar to regular moviegoers and remained in
 their collective memory. Images of particular movie stars became part 
of collective memory. During cinema visits, people could watch newsreels
 of news stories from around the world. For the first time in history a 
mass audience was able to view certain stories, events, and scenes, all 
at the same time. They could all view how for instance the Hindenburg disaster was caught on camera and see and remember these scenes all at once. 
When television became a global mass entertainment medium in the 
1950s and 1960s the collective memory of former cinema visitors 
increased when various films could be repeated endlessly and worldwide 
on television broadcasts. For example, old films like The Wizard of Oz, King Kong and cartoons such as Looney Tunes and Tom and Jerry have been shown internationally and remained on television, through syndication.
 Hereby particular film scenes have become well-known, even to people 
who had not seen these films on their original cinematic release. The 
same applies for television shows like I Love Lucy
 which have been repeated so often over the decades that certain 
episodes and scenes have become ingrained in the public's collective 
memory.
When newsreels in the cinema gradually made place for television news broadcasting,
 it became a habit for mass audiences to watch the daily news on 
television. Worldwide this led to a new kind of collective memory where 
various news events could be shown much quicker than with the cinema 
newsreels. Therefore, certain filmed news stories could be shown on the 
same day they happened and even live during the broadcast itself. 
Millions of people have viewed the assassination of John F. Kennedy in 1963, the landing of Apollo 11 in 1969, the wedding of Prince Charles and Princess Diana in 1981, the death of Princess Diana, and the September 11 attacks on their televisions. In fact, certain questions like "What were you doing when.... happened?",
 usually referring to a large, heavily-mediatized event, have become a 
very important question in the history of the development of the 
collective memory. 
Many people can remember what they were doing when certain 
internationally big media events occurred and these type of questions 
are usually used as a sort of milestone in individual people's life. For example, "What were you doing when you heard that John Lennon was shot?". Due to television repeats, these moments could be relived even long after the actual event happened. The introduction of video stores and video recorders
 in the 1980s, the internet in the 1990s and the DVD player and YouTube 
in the 2000s even increased the opportunity to view and check out famous
 and infamous movie and TV scenes.
Thanks to all these innovations certain scenes have become part 
of audiences' collective memory. This makes it easy for journalists, 
comedians, advertisers, politicians, etc. to make references to these 
scenes, knowing that a large audience will recognise and understand them
 without further explanation. For example, when president Ronald Reagan concluded a speech on March 13, 1985 against the increase of taxes he said "Make my day". Most people in the audience and TV viewers understood the reference to the Clint Eastwood film Sudden Impact and many laughed and cheered in response. The dance moves from Michael Jackson's music video for "Thriller"
 have been repeatedly shown on TV so much that they are instantly 
recognizable and therefore imitated frequently for comedic effect in 
films, TV shows, commercials, etc.
Whenever a comedy show or film features a scene where someone is 
killed or threatened in a shower, most people understand it as a parody 
of Psycho. Various cartoons from Bugs Bunny to Shrek have spoofed famous fairy tales,
 knowing that everybody is familiar with the original stories and will 
immediately laugh at every deviation. The roar of movie monster Godzilla and Johnny Weissmuller's Tarzan yell have become instantly recognizable and easy to put into a context, even without the images.
Numerous TV shows and films such as The Simpsons, Family Guy, Scary Movie, the Shrek films, and the films of Mel Brooks, have referenced, parodied, imitated and recreated these famous scenes, often to the point of overkill. Certain observers, like Kenneth Tynan
 in a quote from his diaries from October 19, 1975 have noted that due 
to the heavy rotation and repeats of all these famous film scenes, often
 even without their original context, they have become part of the 
cultural consciousness. He wrote: 
Nobody took into account the tremendous impact that would be made by the fact that films are permanent and easily accessible from childhood onward. As the sheer number of films piles up, their influence will increase, until we have a civilization entirely molded by cinematic values and behavior patterns.
The influence of television scenes on collective memory has been 
noticeable with children who are able to quote lines and songs from 
commercials, films and television shows they have watched regularly. 
Some young children who have watched a large amount of television have 
been known to react in an unnatural way to certain situations, 
comparable with overacting,
 because they recreate scenes they remember seeing in similar situations
 on television. There have been cases reported of people who've compared
 their own life too much with the romanticized, idealized life depicted 
in films and television series. They try to recreate the happy families 
and perfect love relationships they remember seeing on television or in 
movies.
Not all scenes that were once collective memory are remembered as
 well today. Certain shows, commercials and films that were popular in 
one decade are shown less frequently on television in the next. Thus, 
certain scenes do not rest in the collective memory of the next 
generation. Many references in old Bugs Bunny
 cartoons to Hollywood stars and radio shows who were famous in the 
1940s, are almost obscure to modern viewers. On the other hand, certain 
scenes have remained in the collective memory, due to being constantly 
repeated in other media and are well known even for those unfamiliar 
with the original. For example, even people who never saw the film King Kong know that there is a scene in which the large ape climbs the Empire State Building with a woman in his hand. This could be a negative side effect of the multi-referential nature films and television shows.
Younger audiences, unfamiliar with the original subject being 
referenced in a contemporary film or TV series, do not recognize the 
reference and assume that, for instance a Twilight Zone plot reference in The Simpsons has been thought up by the creators of The Simpsons
 instead of the other way around. In some cases, references or parodies 
of older movies in contemporary films and TV shows are almost comparable
 to plagiarism since they just mimic or imitate a famous scene frame-by-frame instead of adding a funny new element.
In a more general and global perspective, the work of Jeffrey 
Andrew Barash emphasizes the ways in which the mass media select, 
articulate and transmit reported events and thus endow them with public 
significance. Mass media representation of communicated events 
configures them in accord with spatio-temporal patterns and a logic that
 are not simple replicas of the order of everyday experience, since 
disseminated information is charged with an autonomous symbolic sense 
through which public awareness is channeled and sedimented in collective
 memory. This autonomous symbolic sense draws its potency from an 
uncanny ability to simulate direct experience while dissimulating
 the gap which separates it from the immediate life world in which it 
originates. The potency of the mass media format appears in a 
particularly clear light in examples such as the televised Romanian 
revolution, media representation of the Balkan wars, and the mediatized O. J. Simpson trial in the United States.
Music
This notion
 of collective memory overflows into the music and film world. Certain 
references and songs have permeated through culture and invoke certain 
reactions in a wide social group. This makes it easy to make references 
to these scenes and songs, knowing that a large audience will recognize 
and understand them without further explanation.
Soundtracks have been instrumental to cinema and television as a 
subtler form of expression and identity. Music, and more specifically 
soundtracks, can be utilized as an outlet for hope, possibility and 
resistance for everyday people. In Time Passages, George Lipsitz 
acknowledged that "dominant ideology triumphed on television in the 
1950s, just as it did in political and social life" (Lipsitz, 67). 
However, recently movies and television shows such as Insecure, Super Fly, and Waiting to Exhale
 have been able to incorporate music to spread “other” culture and 
foster a community feel. The music not only grounds itself in time but 
also helps personify the complex characters. The combination of new and 
classic songs helps promote these ideals. Sharing music and exchanging 
songs and in turn facilitating a collective memory also connects a 
person to their larger community. In "Record and Hold," Jose Van Dijck 
looked at how this “Shared listening, exchanging songs, and talking 
about music create a sense of belonging, and connect a person’s sense of
 self to a larger community and generation” (Van Dijck, 357). The 
same song can elicit different memories and emotions from different 
people – but they remain a sign of their time and location. Collective 
memory highlights the power of television and popular culture to 
influence politics and offer a glimpse into other people's social 
realities. The music incorporated in popular television and film culture
 can also play a role in young people's development of their identities.
 Van Dijck wrote, "Recorded music also has a formative function: young 
people in particular construct their identities while figuring out their
 musical taste" (Van Dijck 359). Television and movies can have just as 
big of an impact on cultural identities as any history book.