Memory conformity

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Some of the early research in memory conformity involved the Lost in the mall technique.

Memory conformity, also known as social contagion of memory, refers to a situation in which one person's report of a memory influences another person’s report of that same experience.[1] This interference often occurs when individuals discuss what they saw or experienced, and can result in the memories of those involved being influenced by the report of another person.[2] Research on memory conformity has revealed that such suggestibility has far reaching consequences, with important legal and social implications.[3][4] It is one of many social influences on memory.[5]

A major component of memory conformity is source monitoring (or source memory). Source monitoring refers to the process by which an individual determines where they learned certain information (friend, TV show, teacher etc.).[6] A source-monitoring error can lead to an incorrect internal attribution of a memory (a belief that the memory was made from first-hand experience), when in reality that information had an external source (someone else relayed that material/memory).[6] Studies have shown that social interaction can increase source-monitoring errors, with some studies showing that participants attributed their memory to an incorrect source approximately 50% of the time.[7]

Three ways that contribute to memory conformity are: normative influences, information influences and memory distortion.[2] Normative and informational influences on memory are both social influences that can lead to conformity (a modification of behavior in response to actual or imagined pressure from others).[8] Social influence can have a strong impact on the retrieval process of memories. Potential social conformity may be affected by factors such as power and confidence (both in oneself and in the credibility of a collaborator).[9] This influence can alter memories, making them partially or entirely false.[10] Memory distortion, closely tied with the misinformation effect, describes an impairment in memory that surfaces after exposure to misleading information.[11]

Memory conformity is prominent in situations involving social interaction, media broadcasting and eyewitness testimony.[3][5][12]

Memory conformity in and out of lab settings

Famous examples

A fairly recent example of memory conformity occurred in 2003 after the murder of former Swedish foreign minister, Anna Lindh. Immediately after the crime was committed, witnesses were put in a room together so they could not leave the scene of the crime until they were interviewed. The witnesses discussed the scene with each other while in the room, contrary to what they were told to do. The specific descriptions the witnesses gave about the perpetrator upon leaving the room were influenced by each other, causing the police to collect false information about the perpetrator while initially searching for him or her. The perpetrator, Mijailo Mijailovic, was caught on camera and did not match the descriptions that the eyewitnesses gave. Conclusions have been made that the cause of this false search was rooted in witnesses discussion of their accounts with one another, which led to co-witness influence.[13]

Another well-known case of memory conformity happened with the 1995 Oklahoma City bombing. Three employees were working at the location where Timothy McVeigh rented the truck that was used in the bombing.[2] Two of the witnesses originally thought that McVeigh was by himself, but the third believed that there was an accomplice. Later, after the three were left to discuss the event, the other two came to the conclusion that there was indeed a second man who assisted McVeigh.[2] The FBI now believes that this “accomplice” never existed despite their initial search for him or her. The employee who claimed to have seen an accomplice most likely unintentionally influenced the other two employees, causing them to make later claims about an accomplice as well.[13]

A third example is a rather odd event that occurred in 1941. Reportedly, Rudolf Hess, Adolf Hitler's Chief of Staff, flew to Scotland to present The Duke of Hamilton with a peace proposal between Germany and Britain. He parachuted from his aircraft some miles off course and was apprehended and held until two people who had met him years before could be brought to identify him as Rudolf Hess. Prior to their meeting with Hess, the two individuals heard a radio report that Rudolf Hess had parachuted into Scotland and had been apprehended. This report colored their confirmation of Hess's identity when the man in question was shown to them.[14] Despite the fact that about a hundred people in London could have positively identified Hess, the identification was made by these two men who believed it was Hess they were about to identify due to the report they had heard. No other people were ever called to identify Hess in subsequent years, and there has been speculation that a double had impersonated Hess in this event.[15]

Creating memory conformity in a lab setting

Memory conformity and resulting misinformation can be either encountered socially (discourse between two or more people) or brought about by a non-social source.[5] One study found that if an individual was given false information during a post-event discussion, the accuracy of the individual’s memory was lowered, but if the individual was given accurate information during the discussion, then their recall was more accurate. Even when the subjects initial memories were very accurate, individuals who discussed their memory with someone who had witnessed a slightly different scene exhibited a decrease in accuracy due to conformity.[16] Simply hearing another individual’s report on an event is enough to alter one’s confidence in one's own recalled memory.[12] Memory conformity has been shown to occur on tasks involving both free recall and recognition, with study participants being more likely to provide inaccurate details of photographs after having discussed them with another participant.[17]

Memory conformity is frequently created in the lab through the use of photos or videos that depict crime scenes. In many of these studies, participants are led to believe that they had all viewed the same scene, but in reality the videos and photos that they had been exposed to were slightly different for each participant, or they were introduced to a confederate who reports a different memory of the same event. After viewing, the participants are tested on their initial accuracy, and then allowed to discuss their memory with others to see how social interaction affects the accuracy of their memories.[17][18] An early study found that despite having seen different scenes, 79% of pairs were able to come to an agreed-upon conclusion, meaning that nearly half of the individuals conformed to the other member of his or her pair. It is worth noting that, in this study, 98% of participants were initially accurate in their first recall of the scene.[16]

Underlying mechanisms

Social influences

Normative influence, first suggested by Asch in 1955, states that in social situations, people are more likely to make statements that they do not believe in order to conform to social norms and to gain social acceptance.[1][19] For example, research has shown that people who have social interactions after an event are more likely to change their thoughts about the event to something other than what they actually witnessed.[18] In one experiment, 60% of participants reported findings that they could not possibly have witnessed.[18] Further highlighting the social influence on memory conformity, studies have shown that social avoidance is linked to a decrease in memory conformity in that those who are inclined towards social avoidance are less likely to be influenced by others, and therefore less likely to experience memory conformity.[20]

Information influence describes a kind of conformity in which people tend to report what someone else has stated previously because they depend on the other person to resolve uncertainty. People are more likely to conform if they believe that their information source had more time to learn the materials, had better visual acuity, or expressed high confidence in their judgment.[1] One study found that those considered to be high-power individuals are more likely to influence those deemed to be low-power. High-power people are more likely to express themselves and lead discussions, while lower-power individuals will tend to follow and depend upon the more confident individual.[10] Research has also shown that the strength of a relationship between individuals can affect their levels of conformity. Studies exploring levels of conformity between acquaintances and friends, and between strangers and romantic partners show that pairs of individuals with stronger relationships are more susceptible to memory conformity.[13]

Memory distortion

Memory distortion occurs when people report information that has been suggested after an event.[1] Information presented after the encoding of a specific memory is called post-event information (PEI). Distortion of previously encoded memory due to the introduction of new PEI is called retroactive interference.[21] One can experience distortion due to PEI when those who witnessed the same event or took part in the same experience talk about what they saw or experienced.[18] Information acquired during a conversation with another eyewitness about a previous event can create false memories about the initial experience.[22] In a study about eyewitness testimony and memory conformity, two different groups were tested on the validity of their recall. Both watched the same video, but only one group was allowed to discuss the events in the video before the eyewitnesses had a recall test. According to the study, "a significant proportion (71%) of witnesses who had discussed the event went on to mistakenly recall items acquired during the discussion".[18] In the experimental group, the post-event discussion worked to significantly distort witness memory.

A number of factors can work to create this post-event memory distortion. Hindsight bias, the tendency to alter a previous judgement in the face of new information, and source misattribution (see source-monitoring error) work to create memory conformity through post-event memory distortion.[23]

Important variables in memory conformity

Age

Researchers believe that old age and subsequent declines in memory may cause individuals to rely more heavily on external aids such as conversations with others to improve recall.[18][24] This research would suggest that older adults are more susceptible to social influences on memory conformity. One study examining suggestibility found that older adults (average age 76) experienced more memory distortion when introduced to misleading information than did young adults (average age 20).[21] Despite these findings, another study examined levels of conformity following group discussion of a mutually witnessed event, but significant difference in the performance of younger and older participants was not found.[18]

On the other end of the spectrum, children may also be more susceptible to memory conformity than young adults. One study found that when children (ages 3–5) were asked to freely recall an event with a co-witness (who had seen a slightly different version of that same event), both children expressed social conformity in the presence of the co-witness and also exhibited memory distortion in an independent factual test afterwards.[25] Other studies have gone further and found enhanced suggestibility and comparatively worse memory recall with younger children (ages 3–4) than older children (ages 10–12).[21] Other studies have shown that adolescents are much more susceptible to peer influence and may therefore be more susceptible to the social influences of conformity than are young adults.[26]

Confidence (or lack thereof)

An individual is more likely to conform their memories to another's if the individual is uncertain about the accuracy of his or her own recall.[16] Confidence plays an important role in uncertainty: people who are less confident are more likely to conform to the reports of others whom they suspect of having a better memory.[27] This effect was demonstrated in a study that involved showing pairs of participants a set of photographs of a crime. Some photos contained images of an accomplice, while others did not. Immediately after seeing these photographs, participants were asked about the presence of an accomplice in the photographs, as well as their level of confidence in their reports. Initial reports were highly accurate, but after being placed in pairs where each person had seen a slightly different photograph, this pattern changed. Seventy-five percent of the pairs exhibited memory conformity, with one half of the dyad conforming to the other. In almost every case, the less confident person in the pair accepted the more confident person’s memory as the correct one.[16]

Internal confidence at the time of memory encoding also affects general social confidence levels. An individual's reliance on another person's memory is constantly changing as the initial encoder takes into account the conditions under which he/she first perceived the event, as well as the conditions (or believed conditions) under which another individual perceived that event.[28] One study showed that levels of memory conformity between individuals varied based on confidence in the comparative quality of initial viewing conditions. Study participants who thought that they had had less time to view a scene than did another individual were much more likely to conform to that individual's report of an event, while participants who believed their initial viewing window to be longer were less likely to conform.[28]

Group size

Studies have shown that there is a negative relationship between social influence and group size (meaning there is a stronger relationship with a smaller group).[29] Researchers suggest that the influence of group size on conformity is determined by the absence or presence of dissenters, or those disagreeing with the larger group. The presence of dissenters works to decrease the overall group certainty and group unity, which decreases social conformity amongst group members, thus increasing individual internal reliance.[30] Research suggests that the clarity of a participant's recollection of a memory plays a role in within-group recollection: as clarity and internal confidence increase, the pressure to conform to the group decreases. The same research goes on to show that false reports from confederates within a group influence participants more heavily when they are not confident in the accuracy of their memories than when they are internally confident in the accuracy of their memories.[30]

Social anxiety

Researchers report social anxiety as having two significant components: fear of negative evaluation and social avoidance. It has been suggested that people with a fear of negative evaluation are more likely to be influenced by their peers, while those with a tendency for social avoidance are less likely to be influenced by their peers.[31] The individuals concerned with negative evaluation are more likely to comply, as disagreeing with their peers is seen as having a higher cost than the cost of being wrong. Individuals with high levels of social avoidance, on the other hand, place less value on the information provided by others, and are less likely to pay attention to it, resulting in a lower level of conformity.[26]

Resisting memory conformity

File:Explanation of pre and post warnings agaisnt memory conformity.png
Timetable of prewarnings and postwarnings against memory conformity

Prewarnings are warnings given to individuals after an event but before social interaction (when misinformation can be introduced). These warnings are meant to guard an individual against potential memory conformity. They can be warnings against the credibility of a witness or any other attempts to encourage the individual trust internal sources and resist external conformity.[11][32] For many lab experiments, these prewarnings have consistently been effective in decreasing memory conformity.[33] Some prewarnings can work paradoxically to increase memory conformity by overly sensitizing the initial viewer, who then mistakenly incorporates incorrect post-event information into their initial memory.[33]

Postwarnings are post-event attempts to reduce conformity. The misinformation effect can occur when the memory of an eyewitness is influenced by misinformation that is presented after an event.[11] Studies have found that social "postwarnings," like characterizing an individual as having low credibility after the misinformation has been introduced, can reduce the misinformation or memory conformity effect.[9] The success of postwarnings depends on the motivation of the individual to be accurate and the individual's perceived threat of being unduly influenced. Even in the face of these postwarnings, many individuals still show memory conformity.[33] Some research has even shown that postwarnings can cause witnesses to overcorrect their memory exclusion and to neglect to report correct memories that were appropriately gained during the time or experience in question.[34]

Despite that, other studies have found that postwarnings were an effective way to reduce the memory conformity effect.[9] In one experiment, participants were first shown a crime video and then presented with nonwitnessed details (details not in the original video) either through a discussion group, by reading a report, or by watching another version of the video. All three groups similarly reported nonwitnessed details after the first rendition of the experiment, but when the experiment was later repeated and participants were warned against incorporating details from their post-video groups, all three groups showed a significant decrease in report of nonwitnessed details. This postwarning worked to encourage more sensitive source monitoring, which caused a decrease in conformity.[35]

Researchers have investigated if the timing of these postwarnings is important or not. Some researchers have found postwarnings to be ineffective at reducing memory conformity. In one study that found no results from postwarnings, the experimenters warned their subjects one week after they were misinformed.[22] Another study, which found postwarnings to have a significant effect on conformity, presented the warning soon after participants were exposed to the false information.[36] A more recent study found that postwarnings were ineffective at reducing memory conformity, and that providing these warnings at different times after exposure to misinformation did not matter.[22] However, this specific study was different from others that found postwarnings to be effective because experimenters did not test all of their participants in one session, which means the warnings were given shortly after the initial event was encoded and the misinformation was presented.

Implications

Legal implications

Leading questions can alter eyewitness memory.

The most common cause of the wrongful conviction of innocent people is false testimony due to eyewitness errors.[37] Eyewitnesses can encounter post-event information after witnessing a crime. Post-event information comes in three basic types, the first of which is due to the impact that a biased or leading question can have on altering an eyewitness's memory of the event.[38] The second type occurs when the eyewitness is retold the events that they witnessed.[39] False information included within the retelling is often incorporated into the eyewitness's memories, thus altering their perception of the events that occurred. The third type of post-event information originates from conversations with others. Recent research has shown that there is a critical period for eyewitnesses that occurs before they get to report their side of the story.[40] During this time, they are most susceptible to outside influences contaminating their version of the events.

The effects of witness discussion on memory are even more enhanced when the witnesses know each other well. People are more likely to believe information, regardless of whether it is true or false, when it comes from someone they know—say, a friend or significant other.[13] Such a person could be viewed with more credibility than a stranger for a variety of reasons, including a greater trust and familiarity in the relationship.[4] This kind of pattern falls under a larger trend that the perceived credibility of the person providing external information has significant influence over memory conformity.[1]

The way in which witnesses retrieve memory is also an important factor in the likelihood of an individual expressing memory conformity. Studies have shown that when participants were asked to discuss their memories of a violent crime video in terms of their emotions, they had higher levels of subjectivity and major errors in free recall.[41]

One of The Seven Sins of Memory is suggestibility. Interaction with other people changes the pool of information that one has about an event and can sway one's thoughts on how the event actually unfolded.[16] This suggestibility seems to be the most common way in which post-event information distortion occurs in a legal setting because often, witnesses cannot be prevented from talking to one another. That said, there are multiple factors that affect the potential for suggestibility in a witness. More accurate memories are also less susceptible to memory conformity than less accurate ones.[42] This finding is important for legal situations because it may be logically deduced that a witness with a more accurate memory of the event in question will be less likely to change his or her story after discussing it with other witnesses, and someone with a less accurate recollection could be more prone to conform.[42]

Everyday implications

False autobiographical memories can also occur over time. In a recent study, 43% of subjects remembered a childhood event that they never actually experienced.[43] These naturally-occurring autobiographical memories can span a large temporal range, from recent events to childhood memories. These memories also contain weak perceptual detail, which makes them similar to real childhood memories and thus more believable to the person.[43]

First-born children are also more likely than their later-born siblings to dominate a discussion and encounter conformity errors.[44] In one study, later-born children were more influenced if they had reason to believe that the information given to them was more valid then the information they themselves possessed. First-born children were relatively unaffected by informational value and were more influenced by their motivation to either go along with or to resist the expectations of the majority.[44]

Discussion of memory conformity is also particularly relevant in today's age of mass advertisement. Research suggests that our predisposition to trust the judgment of a group can be affected by political campaigns and advertising, and even work to alter personal beliefs.[45] These brain imaging studies go on to show that conformity can be seen at the neurological level when an individual changes his or her personal beliefs due to social influence (called private conformity). The same work has shown that individuals can outwardly conform by seeming to support a group's beliefs or decisions (public conformity), but without the private conformity and the subsequent neurological changes.[45]

Potential benefits

Analyses of memory conformity typically focus entirely on its negative consequences, such as witness memory distortion; however, there are some benefits to memory conformity. In fact, some psychologists posit that memory conformity more often results in positive outcomes than negative ones.[42] When an individual is not confident in the information he or she alone possesses (high subjective uncertainty), reverting to external sources for help usually has no greater potential for an inaccurate memory report than sticking with the original, shaky memory. When the stakes are not as high as something like a criminal trial, other people are a readily available and highly useful means for helping to recall memories.[46]

See also

References

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Further reading