Are Flashbulb memories special?

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Roger Brown and James Kulik were two researchers who became interested in the reports that people had astonishingly detailed and vivid memories for learning news of some shocking event. These memories were so clear and unrelenting that Brown and Kulik called them Flashbulb memories (FMs). The quintessential example of flashbulb memory is the assassination of President John F. Kennedy on November 22, 1963. What caught Brown and Kulik’s interest was not that people could remember JFK’s assassination but that people could recall the event with accurate detail even 30 years after as well as their personal circumstances when they first heard the news (features which are not seen in autobiographical memory formation.)

Brown and Kulik (1977) introduced the FM concept to express the idea that this type of memory preserves knowledge of an event in an almost unalterable way – that there is a special flashbulb memory mechanism which creates a “snapshot” or permanent record of surprising or unexpected events much like a photograph. Despite this analogy Brown and Kulik went on to suggest that these memories can in fact be incomplete and went on to suggest they have a “live” quality which allows only some perceptual and other details of events to come to mind.

Using data from many studies Brown and Kulik proposed the flashbulb memory hypothesis (FMH). The encoding account suggested that processes occurring at or near to the event instigate the creation of FMs. In response to some stimulus event a degree of surprise is assigned and hence experienced. In contrast, when an event is routine and unsurprisingly, it is not focally attended to and no FM is formed. Even when an event falls between these extremes there is still a potential for FM to form; depending on the personal consequentiality and importance. Once a FM formation has been initiated then the degree of elaboration is determined by the degree of personal consequentiality. This encoding account therefore suggests that FMs are the result of an extreme on a sliding scale; their formation is “special” once an event is encoded as surprising to the person and personally consequential.

Brown and Kulik however went on to propose a neuroanatomical theory of FMs based on the work of Livingston (1967). He proposed a theory known as “Now Print!” which suggested that structures in the reticular formation respond to surprise and other structures in the limbic system evaluate the biological significance of an event. When the biological significance of an event meets a certain criterion the limbic system and the reticular systems cause a memory of all recent brain events above a certain level of organisation to be formed. The “Now Print!” mechanism therefore suggests that FMs are special as they are the result of a unique set of changes in the biology of the body, caused only by an event of some personal biological significance, not simply some mundane everyday occurrence.

Despite Brown and Kulik’s work, Neisser (1982) and Neisser and Harsch (1992) suggested that the evidence for the accuracy and permanence of flashbulb memories is not so exceptional as to motivate the postulation of a separate, special neurological mechanism of memory.

Neisser (1982) put forward the idea that the vivid and lost lasting, accurate memories previously reported were based on the assumption that what the subjects reported was veridical, despite their retrospectical nature and criticised the FMH on four counts: accuracy, encoding, consequentiality and content.

In 1992 Neisser and Harsch asked 44 people “How did you first hear the news of the challenger disaster?” They recorded their subjects’ responses twenty-four hours after the event and also after two and half years. Using an example of one of the 44 participants, RT it is possible to see the confidence in accurate recall shown after two and half years. Asked for a five-point confidence rating on various aspects of memory, RT hit the highest point on the scale (point five) on the majority of questions such as: “where were you when you when you heard about the event?”

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Despite this overwhelming confidence, shown not only by RT but by all of the subjects on a considerable proportion of the answers received, RT was in fact mistaken - when compared to her original response the details had changed. Of the forty-four subjects, none were able to recall the event with the accuracy they did only twenty-four hours after the incident. Neisser argued that because some of the FMs were not accurate they could not have been formed by the actions of a special encoding system, thus posing a serious challenge to the “special memory mechanism” theory of flashbulb memories. Instead, Neisser went on to claim that the encoding of memories for events was simply a result of the strong emotions associated with the event which motivates people to repeat the story and hence - through reinforcement – increase the likelihood of later recall. He proposed that the memories are maintained either through overt rehearsal, that is talking about the event with other people or covert rehearsal which involves repeatedly thinking about the event. In this process, memory is reconstructed by the participant to develop what they believe to be a coherent story. He concluded that “apparently flashbulbs can be just a wrong as other kinds of memories.”

He went on to use consequentiality and surprise factors to argue against a special mechanism in the formation of FMs. He proposed that personal consequentiality is often assigned after an event has been experienced rather than at the time of the incident and hence cannot influence the formation of FMs – on this count however Neisser received counter claims that a shocking event must induce some feelings of consequentially at the time set to some “personal significance levels” (Brown and Kulik, 1977).

In their FMH Brown and Kulik suggest that the surprise element leads to deeper encoding via some special memory mechanism, however Neisser argues that high levels of arousal would act to narrow the focus of attention and hence are not conductive to the encoding of detailed memories.

The Easterbrook hypothesis (Easterbrook, 1959) provides support for this argument which suggests that arousal leads to a “narrowing of attention,” or a decrease in the range of cues to which a particular organism is sensitive. Low arousal would lead to improved performance in many tasks, as the narrowing would prevent distraction, however at high arousal levels attention would be narrowed to such an extent that even task-relevant information would be excluded. This theory therefore gives reason to the inaccuracy in recall (mentioned previously of flashbulb memories.)

Similarly, work by Loftus (1979) lead to an understanding of a common phenomenon known as “weapon focus.” This involves an eyewitness to a crime focusing primarily on the weapon used by the criminal at the expense of other detail about the event. This idea that there is increased memory for one aspect and lesser memory for other details supports Neisser in his rejection of the special flashbulb memory mechanism of detailed recall proposed in the FMH.

Similarly McCloskey, Wible, and Cohen (1988) also used the challenger explosion (26th January 1986) to assess the strong claims of the FMH. According to McCloskey et al. the FMH implies that FMs are a separate class of memories distinguished by virtue of privileged encoding via a special encoding mechanism that confers upon FMs unique characteristics. In order to test the mechanism McCloskey recorded people’s memory using a simple questionnaire consisting of 4 critical questions. On the basis of the responses McCloskey et al. concluded that all of the subjects would have experienced FMs using Brown and Kulik’s concepts; however on closer cross-examination many of the answers were found to be inaccurate and inconsistent. On the basis of these latter findings, McCloskey et al. concluded that there was no need to postulate a special FM encoding mechanism. Similarly Larson (1986) found comparable forgetting using delays to the initial report when studying his own diary entry referring to the murder of the Swedish Prime minister Olof Palme – after 157 days had passed since the entry he was unable to remember the details of the event, despite this he felt confident in the answers he gave. Thus, there is considerable support for McCloskey’s conclusion that the strong version of the special memory mechanism is unsustainable.

Critics of McCloskey et al. (1988) such as Schmidt and Bohannon (1988) have argued that Brown and Kulik never intended to suggested a strong mechanism despite the suggestion of a “live”, photographic metaphor and the neurological suggestion in the hypothesis: “permanent registration… of all recent brain events.” They proposed that Brown and Kulik were referring to a weaker flashbulb mechanism which is less than perfect but is still considerably better or different from recall by ordinary memory mechanisms. McCloskey et al. (1988) disagreed with Brown and Kulik (1977) and Pillemer (1984, 1990) and proposed that well-formed memories do occur however, these experiences may have a personal relevance, frequent rehearsal and uniqueness all of which are assumed to increase the richness, vividness and duration of memories. As long as there is continuity with normal memories then there should be no grounds for hypothesising even a weak flashbulb memory mechanism.

Although the FMH is constantly under attack there is still evidence which supports the idea of a special mechanism operation in the formation of FM. Pillemer (1984) carried out a study to test the FMs associated with the attempted assassination of President Ronald Reagan (30th March 1981.) They tested three groups of participants two independent groups tested at one month and seven months and the re-test group tested at both time delays. Over the whole sample 92% of the subjects had FMs, which is comparable with the FM rate observed by Brown and Kulik for events such as the assassination of JFK. This figure makes for impressive evidence of a high incidence of durable and vivid recollections of recalling information about the attempted assassination of Ronald Regan and possibly other newsworthy events. Although there is evidence for a high incidence of FM, the critical issues for the FMH relate to memory consistency and predictors of the elaborateness of memories. Through further investigation and analysis Pillemer’s study provided strong evidence of FM but did not support the idea that personal consequentiality was a critical factor in FM formation. Although Pillemer’s measure of “impact” (used to measure consequentiality) did not correspond perfectly with Brown and Kulik concept of consequentiality, it seems clear that the attempted assassination did not have wide-ranging personal or national effects.

Memory formation is closely associated with the duel route processing concept, the duel-route model focuses on circuits associated with the hippocampus and amygdale (Mishkin, 1982; Mishkin & Appenzeller, 1987) found within the limbic system. In terms of the FBH it is important to investigate whether these different circuits contribute selectively to the formation of different types of memory – and whether one of these circuits is specialised for the encoding of the highly vivid and durable FMs.

Evidence from Squire (1992) suggested that the hippocampus is involved in the formation of a “simple memory, a summary sketch, a gross trace, an index, a device for constructing unique configurations among stimuli, or for collating widely stored pieces of experience.” Mundane and routine experiences do not lead to the release of hormones that cause the glucose levels to be raised and so “sketch” memories represented in the hippocampus are not attended too and hence receive no special processing. Conversely, when an experience does cause the release of the appropriate hormones, then Long-term potentiation (LTP) (site of neural plasticity where memory formation could take place) circuits (in the hippocampus) respond to raised glucose levels and the memory is consolidated much more effectively into long term memory. Hence the mechanism is “special” in the sense that only selective imputed items receive the addition processing required to store the details of an event.

In spite of squire’s (1992) argument that the amygdala plays no direct role in the formation of memories, there is wide-ranging literature indicating the opposite; that the amygdala is a crucial brain structure in memory formation especially when the memory is emotional. In 1989 McGaugh et al. investigated the mediating influence of the amygdala in the formation of memories for events featuring aversive stimuli and from this has concluded that several neurochemical systems meet in the amygdala and interact in the presence of increased glucose levels leading to the formation of FMs, when the glucose levels remain unchanged no FMs will occur.

Unlike the hippocampus and amygdala theories of FM formation the multi-attribute suggestion (Dewhurst and Conway (in press); Johnson, Hastroudi, &Lindsay, 1993) proposes that FM may be represented in terms of their attributes and distributed across may brain sub-systems. Kesner (1991) went on to develop a neuroanatomical model to try and capture the multi-attribute aspect of memory; in his model there are two broad sets of brain processing structures: the data based and the expectancy based systems. From his model he was able to conclude that multi-attribute memories for events low in personal significance and emotion (that is everyday memories) will have reduced representations for processing occurring in the amygdala, on the other hand FMs will have representations in the amygdala and other brain structures such as the caudate. It is this complete representation in the data-based processing subsystems that gives FMs their distinguishing features of being vivid, durable and well-remembered. The memories are so clear simply because more information is reserved and the durability is a result of a more elaborate cognitive “map” of processing in the subsystems. In conclusion FMs occur when all or the majority of data-based processing sub-systems are active.

Overall then it seems that the neurobiology of the brain plays a crucial role in FM formation. The evidence generally supports Livingston’s (1967) original “Now Print!” model although the specific actions mentioned have not received much support. The evidence does seem to suggest a special flashbulb memory mechanism in that the encoding of emotional events differs from the encoding of non-emotional occurrences. The FMH proposes that FMs when compared with other types of memories have privileged encoding and this is supported by the brain neurology studies and theories.

Brown and Kulik (1977) outlined a clear and simple model that identified and expressed the nature of a special type of memory that they called FM. Using some of the extensive amounts of investigations carried out in this research area it seems clear that Brown and Kulik were, at least to some extent correct; there certainly is a discrete class of memories for events that are emotional and important personally and sometimes surprising. The reported memories are more detailed and long-lasting that most everyday autobiographical memories, however the accuracy of the memories has been questioned. Additionally, the evidence from neurobiological studies of memory strongly suggests some special memory system which gives rise to some preferential encoding of FMs . Using a culmination of the evidence it seems that the FMH needs revising rather than complete rejection or acceptance. According to Martin Conway (1994) a useful revision would be to ensure that the relation between FMs and goals and plans formed a more central element in the FMH because FMs are records of times when personally important plans require urgent revision. Another useful revision would be to ensure a more clear definition when expressing what is meant by FM, concepts such as “personal consequentiality” and “emotion” are far too general. Finally the proposed function of FMs is to preserve knowledge of event of biological significance; since studies have become more advanced it seems that FMs can occur in a full range of circumstances hence casting a shadow on the reliability of this concept.

References

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