Eyewitness testimony refers to an account given by people of an event they have witnessed. For example they may have to give details of a crime they have seen.
Research into eyewitness testimonies has found that they can be affected by many psychological factors:
- Anxiety / stress
- Reconstructive memory
- Weapon focus
- Leading questions
Anxiety / Stress
Anxiety or stress is almost always associated with real life crime or violence.
- Deffenbacher (1983) reviewed 21 studies and found that the stress-performance relationship followed an inverted U function proposed by the Yerkes-Dodson (1908) curve (see above). This means that for tasks of moderate complexity (such as Eyewitness Testimony), performance increases with stress up to an optimal point where it then 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 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 remarkably accurate memories of the event. The police interviewed witnesses, and 13 of them were re-interviewed 5 months later. Recall was found to be accurate, even after a long time, and the two misleading questions inserted by the research team had no effect. One weakness of this study was that the witness who experienced the highest levels of stress was closest to the event, and it may be this that resulted in higher accuracy rather than their stress levels. The Yuille and Cutshall study study illustrated two important points:
- There are cases of real life recall where memory for an anxious / stressful event is accurate, even some months later.
- Misleading questions need not have the same effect as has been found in lab. studies.
Barlett's theory of reconstructive memory is crucial to an understanding of the reliability of eyewitness testimony as he suggested…