Eyewitness testimony

Research

Deffenbacher (1983) performed a meta-analysis of 21 studies examining the role of anxiety in the accuracy of EWT, finding heightened anxiety tended to negatively affect the memory recall of eyewitnesses. This again suggests that anxiety can divert attention away from important features of a situation.

Repression

However, Christianson and Hubinette (1993) studied the recall of witness to real bank robberies, finding contradictory evidence, in that increased arousal led to improvements in the accuracy of recall, suggesting that anxiety-creating situations don't always divert attention from important features of a situation

Repression is used as an explanation of anxiety can affect the accuracy of recall.

Freud (1894) argued that anxiety hinders the recall of memories, as he saw forgetting as being motivated by the traumatic content of memories. Access to memories would be barred, so as to protect individuals from the emotional distress caused.

Yerkes-Dodson Inverted-U Hypothesis (IUH)

Eyewitness testimony (EWT)

Deffenbacher (1983) used the IUH to explain how anxiety levels affect the accuracy of recall of events experienced. The IUH sees moderate amounts of anxiety as improving the detail and accuracy of memory recall up to an optimal point, after which further increases in anxiety lead to a decline in the detail and accuracy of recall. The findings of research have been used to investigate whether this is true, though it is difficult to reach any firm conclusions.

Evidence provided by those recalling an event who were present when the event took place.

Jurors often find EWT vitally important in making their decision and yet in 75% of cases where individuals were found by DNA evidence to be wrongly convicted, the original guilty verdict was based on inaccurate EWT.

The influence of Schema

Memories aren't accurate snapshots of events. They are reconstructions of events which are influenced by schemas.

Facts may be distorted due to the schema of the witness 'simplifying' the information presented, filling in gaps in their knowledge.

Research

Loftus (1975) conducted a study where participants watched a video of a car ride and were asked "how fast the car was going when it passed the white barn?". Loftus found that 17% of participants recalled seeing a barn a week later - although there was no white barn in the original video. These results support the idea that post-event information added to a memory after the event has occurred can affect memory recall.

Factors affecting EWT

Psychological factors can affect the EWT, such as:

Leading Questions

Anxiety/ stress

Leading questions are questions that increase the likelihood that an individual's schemas will influence them to give a desired answer. Post-event discussion concerns misleading information being added to a memory after the event has occurred, with research indicating that false memories can be stimulated by misleading post-event experiences.

Reconstructive Memory

Anxiety

Weapon focus

"an unpleasant state of emotional arousal"

Leading questions

Real-life events such as violent crime, often have such a high anxiety content that can affect recall. This makes EWT research difficult due to the lack of emotional involvement for the participants who watch artificial scenarios.

Weapon Focus

Research

Bartlett (1932) found that when Western cultural participants were told a Navajo Indian story, "The War of the Ghosts", that didn't make sense from their cultural viewpoint, their memory of the story became distorted with details of the story being changed to fit a Western cultural viewpoint. This illustrates how memory can be affected by cultural schemas, perceptions of what happened from a particular cultural viewpoint.

Loftus et al (1987) stated that there must be a "weapons effect" which may affect the reliability of an eyewitness. This effect occurs during a violent crime; more attention is focused on the weapon being used, rather than details such as the culprit's face. This can mean that the eyewitness has no detailed recollection of the culprit or some details are incorrect.

Reconstructive Memory

Research

The process of recalling an event is not entirely accurate due to the fact that the memories are reconstructions of what has occurred. This means that it is possible for a memory to be distorted by false information which has originated from the individual's schema.

Expectations based on past experience, knowledge, emotions, context, attitudes and stereotypes can lead to the evidence given by the witness being unreliable.

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 chequebook. 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 chequebook version

EYEWITNESS TESTIMONY