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GUIDELINES ON MEMORY AND THE LAW: Recommendations from the Scientific Study of Human Memory
by The British Psychological Society
Guidelines on Memory and the Law: Recommendations from the Scientific Study of Human Memory. Leicester: Author, 2010
Excerpt: pages 10 – 12
3.i AUTOBIOGRAPHICAL MEMORY
In general the type of memory we are concerned with here is known as autobiographical memory (3.25). The current view is that autobiographical memories are mental constructions that consist of various types of information. Two important types of information are episodic memories and autobiographical knowledge (3.23).
- Episodic memories represent information derived from specific experiences, often in the form of visual mental images although other modalities may also feature, e.g. auditory, olfactory, haptic (touch), and even propriorception (body configuration), etc.
- Autobiographical knowledge represents factual and conceptual knowledge about a person’s life, for example, ‘I went to St Bede’s School’; ‘I didn’t like school’; ‘I was good at English’; ‘John Smith was my best friend’; and so on.
When a person recalls an autobiographical memory, then, these two types of long-term memory representation are brought together and a person consciously experiences episodic memories of specific aspects of the past and conceptual knowledge that acts as a personal context for the episodic memories, locating them in a person’s life and providing a personal, self-relevant, meaning for them (3.15).
It is widely established that adult memories of specific events experienced after about the age of 10 years can be either: (i) highly accurate (3.21); (ii) highly inaccurate, and sometimes wholly false (3.22, 3.31, 3.32, 3.33 & 3.35); or (iii) include both accurate and inaccurate reports relating to different aspects of the same episode (3.24, 3.40 & 3.41). For example, it has been found that some memories of traumatic events, such as memory for being in a concentration camp, memories of traumatic events from the second world, etc. are highly accurate, even many decades later, when evaluated against accounts taken close in time to the actual experience. Similarly, vivid memories of one’s personal circumstances when learning of important and surprising items of public news – the assassination of JFK, the moon landing, the death of John Lennon, the space shuttle Challenger disaster, the resignation of Margaret Thatcher, 9/11, to name but a few – have also been found to be highly accurate and to persist over many years. Set against this are findings, for many of the same events, of wholly false memories and memories that are partly accurate but which contain clearly false details. These are false details of which the rememberer is unaware and when the impossibility is finally pointed out they are usually highly surprised about.
The references cited above provide many examples as well as formal research findings but one case which was recently reported, appropriately by a member of the legal professions, is highly illustrative and it is described here to provide a good example of how highly vivid memories can turn out to be wrong:
A middle-aged man recalled his father distracting him when he was young boy (about 4-years-old) by asking him who was the first man on the moon. He had been intensely interested in the moon landings when he was a young boy and this incident occurred while his father was on the telephone to his mother, who had just given birth to his younger brother. My informant had a vivid and fond memory of his father placating him in this way; he was highly agitated by the birth, and in his memory he could ‘see’ his father on the telephone and almost ‘hear’ his voice. It was only decades later that he realised that his brother had been born in 1968, one year before the first moon landing.
So these significant public events can be remembered vividly, but not necessarily completely accurately.
The references listed below provide many examples of these types of memories and, it should also be noted, many examples of vivid memories that as far as it has been possible to establish are correct. Distinguishing between the true, wholly false and partly false vivid memories of healthy adults is impossible currently unless the content of the memories contains an obvious impossibility or contradiction. Even then such a distinction may not be possible. In the ‘moon landing’ memory just described it seems likely that the event recalled probably did occur but at an earlier or later date and on a different occasion and has been transposed in memory, for what reason we do not know, to a more significant date.
In normal populations, it is easy to induce major memory errors and wholly false memories (3.16, 3.24, 3.30 & 3.32), to mislead witnesses about details of staged events, and to increase the confidence of others in the accuracy of a falsely reported memory (3.39). Here are two examples of how malleable and how misleading memory can be (note that these are merely illustrative examples from many different and convergent lines of research):
- In one series of studies (3.30) university students were asked to take part in an experiment in which they were to recall childhood memories as best they could. In order to facilitate recall the researchers wrote to each student’s parents and asked them to provide a short list of events from the student’s childhood that they thought the student would remember. Students were presented with a brief description of each event and were asked if they remembered it. Unknown to the students, a false event that referred to attending a wedding and knocking over a bowl of punch was also inserted into the list. About one third of the students ‘remembered’ the false event and in subsequent recalls elaborated and integrated it with their other childhood memories. Moreover, when instructed to try to bring to mind visual images of each event as an aid to remembering it, even more students developed the false memory (an effect now known more generally as ‘imagination inflation’, 3.24 & 3.32).
- In an experiment (3.14) that featured a mock trial of a bank robbery, mock jurors were asked to judge the credibility of the evidence of the witnesses. One set of witnesses described events simply and without any details. For example, the (mock) witness might state ‘as the robber ran out of the bank I think he turned right and ran off down the street’. In another version the same witness (to a new mock jury) would state ‘as the robber, who I remember was wearing a green jumper, ran out of the bank I think he turned right and ran off down the street’. This second version of events was rated as far more likely to be correct than the first. The effect is known as ‘trivial persuasion’ because by inclusion of a trivial or irrelevant but highly specific detail the perceived credibility of the evidence is markedly raised.
Trivial persuasion is often seen when witnesses provide verbatim recall of spoken utterances. In controlled experiments in the laboratory and in field studies of actual witness memories it has been found that such recall is simply not possible. What is recalled of this nature is invariably wrong. All the evidence indicates that we remember the ‘gist’ or meaning of what is spoken and not the exact words. It does not follow from this that the memory that is described is itself wrong, but the recall of implausible details does raise questions about the nature and purpose of a memory so described. Often such descriptions appear to be related to beliefs about memory in both the rememberer and recipient (3.42).
For the above reasons the accuracy of memory is typically studied in the laboratory, where the conditions of learning and memory can be carefully controlled. The accuracy of specific memories formed in everyday life is much harder to judge, and can only be established with any confidence when there is independent evidence relating to the episode in question. Relevant corroborating evidence may include: (i) independent reports that the person was present and did indeed witness relevant aspects of the event; and (ii) consistency of recall of core details over long periods of retention. While (ii) represents weaker corroborating evidence than (i), it can be viewed as a prerequisite for a judgment of reliable testimony. Finally, it should be noted that more general knowledge of a person’s life is considered to be less prone to the inaccuracies known to be associated with memories for one-off, unique, episodic events (3.26, 3.27 & 3.28).