MEMORY

http://www.swgs.wilts.sch.uk/SWGSFiles/Subjects/Psychology/Memorynotes.pdf



Short term memory is thought to be able to store about seven items (plus or minus two, Miller) for few seconds (around 18-30, Peterson and Peterson) only until new incoming information displaces the old. If the information   does not then move into the long term, store it is lost. Recall of long term memory depends on retention and retrieval. Memory tends to deteriorate and so become less accurate with time. This is known as the “retention interval”. As well as being retained, memories must be able to be retrieved. Tulving (1983) suggested that at a given time only a small proportion of all memories are available for retrieval.  


Long term memory- visual, verbal and auditory information- is thought to be coded by meaning, (semantic encoding) then linked to related information and associations. 


Consequently what is recorded is not an accurate copy of the data but an interpretation; what we remember is influenced by what we already know. Details tend to be lost over time and become generalised, sometimes merging with similar memories. Repeated childhood holidays to the same beach will result in blurred and blended memories. How then do we try to remember more about a particular incident?  


A further level of processing is proposed in which longer lasting memory is achieved by attaching meaning and significance to the information (very long term memory – see Bahrick’s study). If little is attached, recall will be less easy.  


Bahrick’s Study 
Evidence on the accuracy of autobiographical memories is conflicting. People can be highly accurate over very long periods of time, or highly inaccurate, depending on the exact circumstances. Bahrick et al. tested participants on their memory for the names and faces of people they had been with at college. Different groups were tested between 3 mo. and about 50 yr after graduating. In the free recall test, participants had to remember as many of their classmates as possible. In the picture recognition test, photographs of classmates and nonclassmates had to be discriminated. In the picture matching test, participants had to pick the face that matched a classmate’s name. 


Bahrick et al. found that there was steady forgetting on the free recall test, but virtually none on the recognition or matching tests, until 30 or so years had elapsed (by which time ageing may have played a role). Of course, exposure to class mates involves repeated “learning trials” and hugely distributed practice, but neither of these factors can be critical because studies of single-event memories can be equally accurate. For example, Wagenaar recorded 1 or 2 events that happened to him each day for 6 yr. Each event was recorded in terms of what  happened, who was involved, and where and when it happened. At the end of the 6 yr period, Wagenaar tested himself by providing either 1, 2, or 3 cues for each event. 


Forgetting as a function of retention interval was quite slow but steady. However, providing further retrieval cues allowed  all  memories to be recalled. Wagenaar selected 10 events which he could not remember given 3 cues, and questioned the other people involved in these events. He found that those people were able to provide him with additional cues which allowed him to remember the events in question. 


Thus none of the events seems to have been entirely forgotten. Memory is also inevitably influenced by higher cognitive interactions with personality, mood and the perceived intentions of the interviewer (emotional factors),  for example Freud’s theory of repressed and recovered memories and flashbulb 
memories. 


Repression and Recovered Memories 
The topic of recovered memory has become very contentious recently as a result of legal cases in which the primary evidence of (say) childhood abuse is from memories that have allegedly been repressed and then recovered. To the extent that long-term memory can be unreliable, the idea of recovered memories is rather implausible. 


Perhaps some of the people who claim to have recovered memories of childhood abuse are being tricked by their memories in the same way as participants in laboratory experiments can be? What is the relevant evidence? The best reason for believing that recovered memories might be of use is that, it is quite hard to show that post-event information actually destroys the original memory trace. 


On the other hand, there are plenty of reasons to be sceptical about claims of recovered memory and about the notion that memories can be repressed. For instance, Loftus cites a study of children who had witnessed a parental murder but which was unable to find a single child who had repressed the memory. On the contrary, the children were continually besieged by thoughts about the murder. Pope and Hudson review published research and conclude, controversially, that no convincing evidence of recovered memory of abuse currently exists. 


Reconstructed memory 
Additionally, memory is influenced by schema theory.  Bartlett in 1932 introduced the idea of  'schemata' to explain the observation that when people remember or reconstruct stories the recall is not accurate. People typically omit some details, and reconstruct the story in the light of their own experience and knowledge. He proposed that the story is stored in memory in a pre-formed schema based on prior knowledge. 


Recent research endorses this observation. In one reconstruction study by List (1986) subjects were asked to view a video with eight different acts of shoplifting. The acts that were rated as highly probable were remembered better than those rated as less probable. Subjects also falsely ‘remembered’ some events that were highly probable but had not actually occurred. Particularly with repeated experiences,  information specific to one episode tends to drop out while information common to other similar episodes is incorporated into the general schema and retained. A kind of blended  memory is formed. It is thought that information is not stored in distinct compartments and does not remain inert but is dynamic. However, if the information is particularly unusual, distinctive or emotional in relation to the general experience, it may be retained.   


Flashbulb Memories 
It was formerly considered that "flashbulb" memories for dramatic, highly important and emotionally charged events remain fixed. This view is challenged by recent research (Christianson, 1989, Neisser and Harsch, 1992).  


Data on “flashbulb” memories eg: Neisser and Harsch’s show that we do forget even our flashbulbs. They studied students’ memories of the Challenger space-shuttle disaster. The day after the accident, participants described the circumstances in which they heard the news. They answered questions such as: what time was it? how did you hear about it? where were you? who else was there? etc. Then 2½ years later they were questioned again. 


The data revealed an amazing amount of misremembering. In fact, only 3/44 participants remembered accurately what they were doing. Most were mistaken in some respect, and 11/44 participants were entirely wrong and gave reports that were complete inventions.  


One explanation is the extent to which subsequent thinking about an event leads to the construction of a personal narrative with which the initial memory becomes  integrated, and that this narrative leads to assimilation and alteration. Because flashbulb events make for a good story, people tend to add spurious details, which they are less likely to do with mundane events. McIntyre and Craik (1987) showed memory for facts is better than that for the source of those facts, so people retain the information but are unable to say how they know it or where it came from. They also showed that memory for dates and times is notoriously unreliable, probably because there are fewer links for this kind of information to other knowledge.  


Anderson, Cohen and Taylor comment that there is, also, a possible effect of "demand characteristics" of the task. When people are asked to repeat information they have already given they usually assume that the first account is unsatisfactory in some way and may try to rectify this by supplying more and different details (Edwards and Potter 1992). Tversky and Marsh (2000) showed that when people retell events they take different perspectives for different audiences and purposes. 


Remembering and Forgetting and the use of leading questions in police interviews 
If memory cannot be retrieved, it is lost. 


Experience of retrieval failure suggests that finding the right cues and hints can result  in successful recall. This is also known as cue-dependent forgetting. 'Blocks' may persist for long periods to even trivial information. 'Pop-up' recall may occur later, spontaneously or in response to a different cue. 


Free recall is where open questions are asked and no cues given. In cued recall closed questions containing suggestions as to the target information are used. This may cause problems in that it may affect the accuracy of the recall, provoking falsely ‘remembered’    details. On the other hand it may also trigger far better and more detailed recall than by open questions.  


It has been shown that closed questions may cause shifting responses under repeated questioning of child witnesses, while open-ended questions do not impair accuracy.   


Gisli Gudjonnsen (1992) suggested that although cued recall after free recall can elicit  more full testimony, cues may influence the recall and be misleading, amounting to post-event interference. To distinguish between such real/perceived memory and suggested/confounding memory Gudjonnsen recommends asking further questions. 


'Real' memories contain more sensory information such as colours, size, shape and sound. 'Suggested' memories tended to be long winded but lacking in vividness. These observations are further explored in the paper by Schooler, Gerhard and Loftus (1986). They confirmed that 'real' memories contain more sensory and geographic detail and are expressed with greater confidence. 'Suggested' memories are described with more words, verbal 'hedges', justifications, rationalisations and descriptions of function rather than actuality. 


The effectiveness of cues in aiding recall has been used by the police in the cognitive interview technique in which witnesses are encouraged to remember as much detail as they can about an event, no matter how irrelevant, as any detail may trigger further recall of more relevant information. One of the obvious differences between conventional interview techniques and cognitive interviews is such a difference in the relative use of free and cued recall. In conventional interviews, people are invited to answer mainly closed questions with brief details. In later statements (possibly cognitive interviews with their solicitor) questions are more often open and people are are encouraged to give as much detail as possible. 


Hypermensia-  Remembering More 
Hypermnesia (enhanced memory) describes the observation that people remember more details with repeated recalls. In 1987 Payne et al showed that this is a reliable phenomenon even when the time between recalls of word lists is varied. He also showed that it is more common when subjects are asked to recall high imagery  material than low imagery material. Pictorial material produced hypermnesia in 95% of cases compared to verbal material in 50%. This is thought to be because the more elaborate or complex material can give rise to greater numbers of recall cues which then increase the chances of recall over time. 


Bluck, Levine and Laulhere (1999) demonstrated the phenomenon of hypermnesia in autobiographical material. This occurs when individuals are seen to recall more information over repeated sessions even after they thought they could recall nothing further. Other workers have shown that personal autobiographical memories are highly imaginally recorded. 


Over time and repeated recall there may be a tendency to confabulate and produce more false responses. Even when the material to be recalled is a videotape    e.g. of a crime (Scrivner and Safer 1988) there is an increase in error rate with repetition.  


In Bluck, Levine and Laulhere's study the memory tested was for the verdict of the OJ Simpson trial. The numbers of errors increased in successive recalls cumulatively, although the ratio of errors to accurate information did not change over time.   This means that the increased information recalled in subsequent interviews was not due to an increased error rate, and confabulation was not the reason for the hypermnesia. 


In three interviews conducted within one hour the information recalled increased between the first and second interviews. Between the second and the third, although no new information was recalled, previously-recalled information was 'forgotten`' or omitted, so no overall increase was shown.   Their interpretation of this result is that autobiographical memories are not traces that are retrieved and described but are 
reconstructed  from event-specific knowledge. The exact form is guided by the social and situational context in which they are recalled. Thus no two reformulations can be absolutely identical.  


Memory Enhancement Techniques 
To improve long-term recall, for enhanced memory/hypermnesia, therapists can draw on techniques as hypnosis, and repeated testing, But hypnosis and other techniques probably do not improve memory. As an illustration, Dinges et al. presented participants with 40 slides of common objects to remember. Participants performed an immediate forced recall test (R1), which was repeated a week later (R2). This second test was then followed by 6 more tests (R3-R8) at intervals of a few minutes. For half the participants, the first 5 of these tests were done fully awake, for half under hypnosis. For the final test (R8), recall was done while all participants were awake. Although repeated testing led to large improvements in recall, the results provided no evidence that hypnosis improved recall further. Hypnosis did have one effect, though: Dinges et al. found that it increased participants’ confidence in their responses.