How reliable is Eyewitness testimony, and what can be done to improve it?

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How reliable is Eyewitness testimony, and what can be done to improve it?

To answer this question in depth is beyond the scope of this work, which will explain briefly  how human memory works; factors effecting the memory process; how a memory is recalled, with emphasis on eyewitness testimony; and concluding with steps to improve the quality and quantity of information retrieved from eyewitnesses.

“Only a fraction of the signals that reach us from the outside world can be registered by our senses. Even fewer are converted into memories.” (Lloyd-Bostock, 1988: p5).  When we experience an event, all of our senses are receptors of information, which we then process for memory, however we are selective. We cannot remember everything as if videotaping our lives (Ainsworth, 1998). This filtering of information is recognized in Broadbent’s ‘Filter Theory’ (Milne & Bull, 1999).

Memory begins with ENCODING (Milne & Bull, 1999), where sense is made of the representation of the event. Attention is paid to the important and relevant. This attention-worthiness can be affected by our life experiences, attitudes, and expectations, causing each of us to selectively attend to different aspects of the same event. (Fruzetti, Toland, Teller & Loftus, 1992). Next, the experience is STORED (Milne & Bull, 1999). The encoded information is placed in memory where it will remain, barring some destructive trauma, until required for the final stage of the process, RETRIEVAL, the recall of the event (Milne & Bull 1999). At any stage in the process, one or more of the components can fail.

Memory is constructive, in that we build a meaningful picture of what our senses are receiving, filling in the gaps, an example of which was provided by Trankell (1972). A lawyer travelling in a taxi, had reported seeing the door of a car ahead open, an old man fall out, and lay in the road. It was later found that the old man was a pedestrian who had been knocked down, not a passenger in the car ahead. Based on fragmented visual information, he had constructed a feasible reality. (Lloyd-Bostock, 1988)

Generally, it has been found that we recall an event better if it did not involve violence (Clifford & Scott, 1978). Experiments using film of a fictitious robbery, depicting varying levels of violence, resulted in viewers of the violent version being 7 times less likely to accurately recall significant detail than those viewing the non-violent version (Loftus & Burns, 1982). It is suggested that the shock of witnessing a real crime interferes more with the processing of information ( Lloyd-Bostock, 1988). Stress is also shown to interfere with recall (Holmes, 1974). Some researchers argue that participants are better at recalling an event than those who are bystanders (Cohen & Faulkner, 1988; Yuille, Davies, Gibling, Marxsen & Porter, 1994) while others have found that involvement has no measurable impact on the accuracy of recall (Saywitz, Geiselman & Bornstein, 1992; Farringdon & Lambert, 1993; Roberts & Blades, 1998)

Ebbinghaus (1885/1964) conducted early experiments into learning and retention, describing the ‘Serial Position Effect, where items at the beginning  - ‘primacy effect’, and the end ‘recency effect’ of a list, were more likely to be remembered than those in the middle. This was developed and expanded in the 1960’s by Broadbent, and by Atkinson and Shiffrin (1971) in their ‘Buffer Theory’. Which describes information entering a ‘sensory store’ where it remains briefly. If attended, the information is then passed to the ‘short term memory’(STM) which acts as a buffer to prevent ‘long term memory’(LTM) having to process too much information at one time. Short term memory can hold 7 (+- 2) chunks of information. Early chunks stay longer in STM and are therefore more likely to be passed to LTM, and later chunks are still in STM and easily recalled. (Ainsworth, 1998)

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There are many factors which can  negatively effect recall, (Milne & Bull, 1999):-

Sensory Information gained from one sense, can be distorted by another. Loftus (1977) demonstrated how visual information could be contradicted by auditory signals. The brain selectively makes sense of the conflict to make it fit with our expectations. Loftus and others expanded further with work on Compromise memory, making sense of the conflict between what we saw, and what we are told happened. The effect is compounded the closer the introduction of the conflicting information, to the requirement to recall (Hall, Loftus & Tousignant, 1984)

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