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Psychology Essay On Eyewitness Testimony

Eyewitness Testimony

Saul McLeod published 2009


Eyewitness testimony is a legal term.  It refers to an account given by people of an event they have witnessed. 

For example they may be required to give a description at a trial of a robbery or a road accident someone has seen.  This includes identification of perpetrators, details of the crime scene etc.

Eyewitness testimony is an important area of research in cognitive psychology and human memory.

Juries tend to pay close attention to eyewitness testimony and generally find it a reliable source of information.  However, research into this area has found that eyewitness testimony can be affected by many psychological factors:

  • Anxiety / Stress
  • Reconstructive Memory
  • Weapon Focus
  • Leading Questions (Loftus and Palmer, 1974)
  • Anxiety / Stress

    Anxiety or stress is almost always associated with real life crimes of violence.  Deffenbacher (1983) reviewed 21 studies and found that the stress-performance relationship followed an inverted-U function proposed by the Yerkes Dodson Curve (1908). 

    This means that for tasks of moderate complexity (such as EWT), performances increases with stress up to an optimal point where it starts to decline.

    Clifford and Scott (1978) found that people who saw a film of a violent attack remembered fewer of the 40 items of information about the event than a control group who saw a less stressful version.  As witnessing a real crime is probably more stressful than taking part in an experiment, memory accuracy may well be even more affected in real life.

    However, a study by Yuille and Cutshall (1986) contradicts the importance of stress in influencing eyewitness memory.

    They showed that witnesses of a real life incident (a gun shooting outside a gun shop in Canada) had remarkable accurate memories of a stressful event involving weapons. A thief stole guns and money, but was shot six times and died.

    The police interviewed witnesses, and thirteen of them were re-interviewed five months later.  Recall was found to be accurate, even after a long time, and two misleading questions inserted by the research team had no effect on recall accuracy. One weakness of this study was that the witnesses who experienced the highest levels of stress where actually closer to the event, and this may have helped with the accuracy of their memory recall.

    The Yuille and Cutshall study illustrates two important points:

    1. There are cases of real-life recall where memory for an anxious / stressful event is accurate, even some months later.

    2. Misleading questions need not have the same effect as has been found in laboratory studies (e.g. Loftus & Palmer).


    Reconstructive Memory

    Bartlett ’s theory of reconstructive memory is crucial to an understanding of the reliability of eyewitness testimony as he suggested that recall is subject to personal interpretation dependent on our learnt or cultural norms and values, and the way we make sense of our world.

    Many people believe that memory works something like a videotape.  Storing information is like recording and remembering is like playing back what was recorded.  With information being retrieved in much the same form as it was encoded.  However, memory does not work in this way.  It is a feature of human memory that we do not store information exactly as it is presented to us.  Rather, people extract from information the gist, or underlying meaning.

    In other words, people store information in the way that makes the most sense to them.  We make sense of information by trying to fit it into schemas, which are a way of organizing information.

    Schemas are mental 'units' of knowledge that correspond to frequently encountered people, objects or situations.  They allow us to make sense of what we encounter in order that we can predict what is going to happen and what we should do in any given situation.  These schemas may, in part, be determined by social values and therefore prejudice.

    Schemas are therefore capable of distorting unfamiliar or unconsciously ‘unacceptable’ information in order to ‘fit in’ with our existing knowledge or schemas.  This can, therefore, result in unreliable eyewitness testimony.

    Bartlett tested this theory using a variety of stories to illustrate that memory is an active process and subject to individual interpretation or construction.

    In his famous study 'War of the Ghosts', Bartlett (1932) showed that memory is not just a factual recording of what has occurred, but that we make “effort after meaning”.  By this, Bartlett meant that we try to fit what we remember with what we really know and understand about the world.  As a result, we quite often change our memories so they become more sensible to us.

    His participants heard a story and had to tell the story to another person and so on, like a game of “Chinese Whispers”. 

    The story was a North American folk tale called “The War of the Ghosts”.  When asked to recount the detail of the story, each person seemed to recall it in their own individual way.

    With repeating telling, the passages became shorter, puzzling ideas were rationalized or omitted altogether and details changed to become more familiar or conventional.

    For example, the information about the ghosts was omitted as it was difficult to explain, whilst participants frequently recalled the idea of “not going because he hadn’t told his parents where he was going” because that situation was more familiar to them. For this research Bartlett concluded that memory is not exact and is distorted by existing schema, or what we already know about the world.

    It seems, therefore, that each of us ‘reconstructs’ our memories to conform to our personal beliefs about the world.
     

    This clearly indicates that our memories are anything but reliable, ‘photographic’ records of events.  They are individual recollections which have been shaped & constructed according to our stereotypes, beliefs, expectations etc.

    The implications of this can be seen even more clearly in a study by Allport & Postman (1947).

    When asked to recall details of the picture opposite, participants tended to report that it was the black man who was holding the razor.

    Clearly this is not correct and shows that memory is an active process and can be changed to 'fit in' with what we expect to happen based on your knowledge and understanding of society (e.g. our schemas).


    Weapon Focus

    This refers to an eyewitness’s concentration on a weapon to the exclusion of other details of a crime.  In a crime where a weapon is involved, it is not unusual for a witness to be able to describe the weapon in much more detail than the person holding it.

    Loftus et al. (1987) showed participants a series of slides of a customer in a restaurant.  In one version the customer was holding a gun, in the other the same customer held a checkbook. Participants who saw the gun version tended to focus on the gun.  As a result they were less likely to identify the customer in an identity parade those who had seen the checkbook version

    However, a study by Yuille and Cutshall (1986) contradicts the importance of weapon focus in influencing eyewitness memory.

    References

    Allport, G. W., & Postman, L. J. (1947). The psychology of rumor. NewYork: Holt, Rinehart & Winston.

    Bartlett, F.C. (1932). Remembering: A Study in Experimental and Social Psychology. Cambridge: Cambridge University Press.

    Clifford, B.R. and Scott, J. (1978). Individual and situational factors in eyewitness memory. Journal of Applied Psychology, 63, 352-359.

    Deffenbacher, K. A. (1983). The influence of arousal on reliability of testimony. In S. M. A. Lloyd-Bostock & B. R. Clifford (Eds.). Evaluating witness evidence. Chichester: Wiley. (pp. 235-251).

    Loftus, E.F., Loftus, G.R., & Messo, J. (1987). Some facts about weapon focus. Law and Human Behavior, 11, 55-62.

    Yerkes R.M., Dodson JD (1908). The relation of strength of stimulus to rapidity of habit-formation. Journal of Comparative Neurology and 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.


    How to reference this article:

    McLeod, S. A. (2009). Eyewitness testimony. Retrieved from www.simplypsychology.org/eyewitness-testimony.html


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    Further Information

    Cognitive Interview

    Eyewitness Testimony

    Elizabeth Loftus and Eye Witness Testimony

    A witness is someone who has firsthand knowledge about a crime through their senses and can certify to its happening and someone who has seen an event at firsthand is known as an eyewitness.

    Witnesses are often called before a court of law to testify in trials and their testimony is considered crucial in the identification and arrest of a suspect and the likelihood of a jury convicting a defendant.
    Eyewitness testimony needs to be reliable as it can have serious implications to the perceived guilt/innocence of a defendant.

    Bartlett’s study involved the Indian folk story ‘War of the Ghosts’. He wanted to investigate the effect of schema on participant’s recall of a story. Participants were asked to read the story and then asked to recall it after a period of time. He found that the story became shorter and participants often added their own interpretation and the whole theme of the ghosts was often forgotten. Bartlett decided that memory is not accurate and is actively constructed using schemas.

    A study by Loftus and Palmer in 1974 looked at the effects of language on recall in eyewitness testimony. They wanted to show that leading questions could have an effect on the memory. Participants were shown a video of a car accident and then, as if they were eyewitnesses they were asked to describe what had happened.

    Specific questions were asked including “about how fast the cars were going when they hit / smashed / collided / bumped / contacted. A week later the participants were asked “did you see the broken glass”. The findings showed that the estimated speed was affected by the verb used in the question. The group with the verb smashed estimated the speed to be 40.5 mph yet the group with the verb contacted only estimated the speed to be 31.8 mph. The stronger the verb the higher the estimated speed, when the participants were asked if they saw the broken glass it was found that out of the group with the verb ‘smashed’ over 32% said they had seen the glass where only 14% in the group with the verb ‘hit’ said they had seen it. There was in fact no broken glass. Our schemas tell us it is reasonable to assume that there would be broken glass at the site of a car accident when the word smashed is used.

    The strengths of the study were that it was a controlled experiment and Loftus could control all the extraneous variables, the study could be easily replicated and it had real life implications for eye witness testimony. There was however some weaknesses in that the study lacked ecological validity, it was ethically questionable and the participants were all students and therefore may not be a representative sample.

    Loftus and Zanni (1975) did another study to show that it wasn’t only a verb that would have implications for the memory but that changing the word ‘a’ or ‘the’ could also have a dramatic effect. Participants were shown a video of a car accident, and then one group was asked “Did you see a broken headlight?” and the other group was asked “Did you see the broken headlight?” There wasn’t actually a broken headlight but the group asked the ‘the’ question assumed the headlight was broken and 15% said they had seen it whereas only 7% of the ‘a’ group answered yes. The use of the word ‘the’ makes the assumption that the car headlight was actually broken.

    In conclusion this essay has shown that eyewitness testimony and those witnesses can be lead into giving what they believed to be true recollections of a crime or incident with the use of different verbs or changing the definite article.

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