In particular, in cases where weapons are involved, fear and anxiety induced by the sight of the weapon may cause witnesses to allocate almost all of their attentional resources to the threatening object, leaving only limited resources to encode other details, such as details about the main perpetrator (Cutler, Penrod & Martens, 1987; Kramer, Buckhout & Eugenio, 1990; E.F. Loftus, Loftus & Messo, 1987; Maass & Koehnken, 1989; Tooley, Brigham, Maass & Bothwell, 1987). This phenomenon is known as ‘weapon focus’. G.R. Loftus and Mackworth (1978) showed that people fixate faster, more often and for longer durations on weapons than on relatively harmless objects, and E.F Loftus, Loftus and Messo (1987) demonstrated that participants recall fewer details about a person holding a weapon than do participants who watch comparable sequences of events without a weapon. Furthermore, in a study by Loftus (1979), participants who saw a man emerge from a laboratory holding a paper-knife covered in blood, accurately identified that person from photos only 33% of the time, whereas participants who saw the same man come out the laboratory holding a pen, correctly identified him 49% of the time. In real life situations, therefore, when one’s life may be at threat, one can only surmise that the weapon focus effect may be magnified.
Information obtained from field reports and interviews with real-life victims and witnesses, however, suggests that eyewitness testimony may be more accurate than laboratory-based studies would suggest. For example, high levels of accuracy and little decay over time were reported for 13 murder witnesses who were interviewed soon after the crime and again 4-5 months later (Yuille & Cutshall, 1986). In fact, the mean accuracy rate of participants who reported the highest levels of stress was 93% in the initial police interview, and 88% 4-5 months later. It is, of course, difficult to measure stress levels objectively in such real-life cases, as other variables confound the issue, and there was no neutral event against which stress levels could be compared (Christianson, 1992). In a study of eyewitness memory and emotional reactions including a total of 110 witnesses to 22 post office robberies, Christianson and Hübinette (1993) reported that witnesses’ recollections of detailed information, such as clothing, were consistent with police reports, but recollections of peripheral information to the main incident (i.e., the time, other people) showed less consistency. It would appear, therefore, that high levels of emotion may not impair memory for the central details of an event. In fact, it may intensify it, but may be detrimental to memory for peripheral details. Furthermore, Foster at al (1984) argue that eyewitnesses may be more likely to remember traumatic events that occur in real life because they may have serious consequences. Participants shown a video of a bank robbery and subsequently asked to identify one of the robbers in a line-up (having been told the robbery was real and that their responses would affect the trial) showed greater recall than did participants who were not given this information. In laboratory-based studies participants may do their best to co-operate and please the experimenter, but they are aware that the suspect’s freedom does not depend on their responses (Cohen, 1993).
A further reason why it has been proposed that eyewitness testimony is unreliable derives from research into schemas and scripts (Bartlett, 1932; Schank & Abelson, 1977), which emphasise that memory is constructive, i.e., our prior knowledge and expectations may influence what we remember about a crime, and therefore eyewitnesses’ recall may be distorted or reconstructed by this information. Schemas and scripts provide us with past knowledge so that we can interpret current situations and thereby help us to infer what is not explicitly stated, because we fill in the missing information to form an integrated memory, i.e., to make sense of what we have seen. As a result, memories become distorted to fit in with prior expectations. For example, we may remember a bank robber as having worn a mask when in fact he was wearing dark glasses, because our memory has been distorted by a schema based on information drawn from TV depictions of bank raids (Cohen, 1993).
List (1986) demonstrated this phenomenon. First, one group of participants were asked to rate various events in terms of their probability of occurring in a shoplifting scenario. She then made a video recording of 8 shoplifting acts, some which had been rated high-probability and some low-probability, and showed it to another set of participants. As schema theory would predict, participants were more likely to recall high-probability rather than low-probability events when their recall was tested one week later. In addition, there was also a greater incidence of participants including high-probability events that did not occur than they did low-probability events that did not occur. Brewer and Treyens (1981) reported similar findings in a study of the effects of schemas on visual memory, with participants left for 35 minutes in an office-like room tending to falsely report the presence of items with high schema expectancy, i.e., pens and telephones. These findings suggest that participants used schemas to encode the visual information during their 35-minute wait, and the schemas influenced recall to include items that were not actually present. Having discussed the constructive nature of memory, the essay will now discuss the effect of post-event information on the memory of eyewitnesses.
Research findings suggest that memory of an incident can be changed or supplemented by subsequent information, such as information introduced during cross-examination and by leading questions. Loftus (1975), for example, showed two groups of participants a film depicting a car accident. When each group was subsequently asked questions about the car accident, the second group was given a misleading question which implied that there had been a barn in the film. When both groups were questioned one week later and participants were asked if they had seen a barn, 17.3 per cent of the group that was given the misleading question reported that they had seen a barn compared to 2.7 per cent of the first group. Loftus (1975) concluded that the non-existent barn had been added to the original memory representation of the event at the questioning stage and was being recalled as part of the original event. Loftus (1975) suggested that misleading information “overwrites” and eradicates the original information. Dodson and Reisberg (1991), however, provided evidence that the original memory of an event is simply inaccessible and is not eradicated. Loftus (1992) now suggests that participants merely ‘accept’ misleading information and regard it as forming part of the original memory. Various other mechanisms have been proposed (e.g. source monitoring, Allen & Lindsay 1998), but there is no general consensus on the mechanisms that may cause eyewitnesses to be misled by post-event information.
It has also been suggested that the way in which a question is worded may prompt false memories. Loftus and Palmer (1974) found that participants’ estimations of how fast two cars were travelling when they collided varied considerably depending on which word was used in the question, i.e., the word ‘smashed’, ‘collided’, ‘bumped’ or ‘contacted’. ‘Smashed’ elicited the highest estimate (40.8 mph), whereas ‘contacted’ produced the lowest (31.8 mph). Furthermore, merely asking participants if they had seen “the broken headlight” instead of “a broken headlight”, after showing a short film of a car accident, elicited an affirmative response from 17% of respondents (Loftus and Zanni, 1975).
An additional factor that has to be taken into account when considering the reliability of eyewitness testimony is the age of the witness. Research indicates that young children and older adults tend to remember information less well than do older children and younger adults (Cohen and Harnick, 1980; Yarmey and Kent, 1980). Flin, Boon, Knox and Bull (1992), for example, found that the recall of children aged 5-6 decreased dramatically over a period of 5 months compared to the recall of adults. This is an important consideration in eyewitness testimony in court, when many months may have passed since the incident for which the witness has to give evidence. Both younger children and older adults also appear to be more susceptible to misleading information (e.g., Ceci and Bruck, 1993), which is an important consideration during cross-examination, for example.
Despite considerable evidence suggesting that eyewitnesses can be misled by false information, it is important to note that witnesses are not always susceptible to misleading post-event information. Loftus (1979) demonstrated that people are not generally misled by information that is blatantly incorrect. Of participants shown slides depicting the theft of a large, red purse from a handbag, and subsequently exposed to information indicating that the purse was brown, all but 2 participants resisted the new information and continued to remember the purse as being red. Furthermore, in view of findings that eyewitness testimony is often fallible and incomplete, psychologists have devised memory retrieval techniques aimed at eliciting more accurate information from witnesses. One such technique is the Cognitive Interview Schedule (Geiselman et al, 1985), which attempts to facilitate retrieval by asking witnesses to recall the context of the incident. Witnesses are also asked to recall every detail – no matter how trivial – and to describe the scene from the perspective of other people who were present at the time. Research indicates that the Cognitive Interview Schedule elicits on average 30 per cent more accurate information than standard interviewing techniques (Bekerian and Dennett, 1993).
In conclusion, a significant body of empirical research on eyewitness testimony suggests that it may be unreliable, though it is not always so. Specifically, stress and high levels of emotion may impair memory for the peripheral details of a crime, but may intensify memory for the main incident. In addition, the essay presented evidence suggesting that memory is constructive, and therefore, that past information may cause interference in the memory of a specific event. Finally, the essay discussed the effect of post-event information on memory. In particular, memory may be affected by misleading questions, by the way in which questions are phrased and by age. However, although a wealth of evidence suggests that eyewitness testimony is unreliable, the cognitive interview schedule has been shown to considerably increase the accuracy of recall. In addition, a significant number of real-life witnesses have shown very high levels of accuracy (Yuille & Cutshall, 1986), and therefore the validity of eyewitness testimony must not be undermined.
References
Bartlett, F.C. (1932) Remembering. Cambridge: Cambridge university press
Barton, S. D. & Warren, L. R. (November 1988) Effects of an emotionally arousing incident on memory for adjacent events. Paper presented at 29th Annual Meeting of the Psychonomic Society, Chicago
Bekerian, D. A. & Dennett, J. L. (1993) The cognitive interview technique: reviewing the issues. Applied cognitive psychology, 7. 275-298
Brewer, W.E. & Treyens, J. C. (1981) ‘Role of schemata in memory for places’, Cognitive psychology, 13. 207-30
Ceci, S. J. & Bruck, M. (1993) The suggestibility of the child witness. Psychological bulletin, 113. 403-439
Christianson, S. A. (1992) Emotional stress and eyewitness memory: a critical review. Psychological bulletin, 112, 2. 284-309
Christianson, S. A. & Hübinette, B (1993) Hands up! A study of witnesses’ emotional rections and memories associated with bank robberies. Applied cognitive psychology, 7. 365-79
Clifford, B. R. & Hollin, C. R. Effects of the type of incident and the number of perpetrators on eyewitness memory. Journal of applied psychology, 66. 364-370
Clifford, B. R. & Scott, J. Individual and situational factors in eyewitness testimony. Journal of applied psychology, 63. 352-359
Cohen, G (1993) ‘Everyday memory’, in G. Cohen, G. Kiss & M. Levoi, Memory: current issues. Buckingham: Open university press
Cohen, G (1996) Memory in the real world. Milton Keynes: The open university
Cohen, G & Faulkner, D (1989) Age differences in source forgetting: effects on reality monitoring and eyewitness testimony, Psychology and aging, 14. 10-17
Cutler, B, Penrod, S. & Martens, T (1987) The reliability of eyewitness identification. Law and human behavior, 11. 233-258
Flin, R., Boon, J, Knoex, A., & Bull, R. (1992) The effect of a five month delay on children’s and adult’s eyewitness memory. British journal of psychology, 83. 323-336
Foster, R.A., Libkuman, T.M., Schooler, J.W. & Loftus, E.F. (1994) Consequentiality and eyewitness person identification. Applied cognitive psychology, 8. 107-121
Geiselman, R, Fisher, R, Mackinnon,D & Holland H. L. (1985) Enhancement of eyewitness testimony with the cognitive interview. American journal of psychology, 99. 385-401
Geiselman, R (1988) ‘Improving eyewitness testimony through mental reinstatement of context’ in G.M Davies & D.M. Thomson (eds) Memory in context: context in memory. Chichester: Wiley
Kassin, S.M., Ellsworth, P.C. & Smith, V.L. (1989) The general acceptance of psychological research on eyewitness testimony: a survey of the experts. American psychologist, 44. 1089-1098
Kramer, T.H, Buckhout, R., Fox, P., Widman, E., & Tusche, B. (1991) Effects of stress on recall. Applied cognitive psychology, 5. 483-488
Lindsay, S (1990) Misleading questions can impair eyewitnesses’ ability to remember event details. Journal of experimental psychology: learning memory and cognition, 16. 1077-1083
List, J. A. (1986) Age and schematic differences in the reliability of eyewitness testimony. Developmental psychology, 1. 50-57
Loftus, E. F. (1975) Leading questions and the eyewitness report. Cognitive psychology, 7. 560-572
Loftus, E. F. (1977) Shifting human color memory. Memory and cognition, 5, 696-699
Loftus, E. F. (1979) Eyewitness testimony. London: Harvard University Press
Loftus, E. F. & Burns, T. E. (1982) Mental shock can produce retrograde amnesia. Memory & cognition, 10(4). 318-323
Loftus, E.F., Loftus, G.R., & Messo, J (1987) Some facts about “weapon focus”. Law and human behavior, 11. 55-62
Loftus, E. F. & Palmer (1974) Reconstruction of automobile destruction: an example of the interaction between language and memory. Journal of verbal learning and verbal behaviour, 13. 585-589
Loftus, G.R. & Mackworth, N. H. (1978) Cognitive determinants of fixation location during picture viewing. Journal of experimental psychology: human perception and performance, 4. 565-572
Maass, A. & Koehnken, G. (1989) Eyewitness identification: simulating the “weapon effect”. Law and human behavior, 13. 397-408
Schank, R. C. & Abelson, R. P. (1977) Scripts, plans, goals and understanding. Hillsdale, NJ: Lawrence Erlbaum Associates Inc.
Tooley, V, Brigham, J., Maass, A. & Bothwell, R. (1987) Facial recognition: weapon effect and attentional focus. Journal of applied social psychology, 17. 845-859
Yerkes, R. M. & Dodson, J. D. (1908) The relation of strength of stimulus to rapidity of habit-information. Journal of comparative neurology of psychology, 18. 459-482
Yuille, J. C. & Cutshall, J. L. (1986) A case study of eyewitness memory of a crime. Journal of applied psychology, 71. 291-301