6. Factors affecting the accuracy of EWT (1) (●ˇ∀ˇ●)

What is the definition of eyewitness testimony? (EWT)

The ability if people to remember the details of events, such as accidents and crimes, which they themselves have observed. Accuracy of EWT can be affected by factors such as leading questions and anxiety.

What is the definition of a leading question?

A question which, because of the way it is phrased, suggests a certain answer. For example, ‘did you see the knife in his left hand’ leads a person to think thats where the knife was.

Who conducted the research on leading questions?

Elizabeth loftus and John Palmer (1974)

What was the procedure?

• They arranged for 45 participants (students) to watch film clips of a car accidents and then asked them questions about the accident.

• in the critical question (a leading question) participants were asked to describe how fast the cars were travelling: ‘about how fast were the cars going when they hit each other?’

• there were five groups of participants, and each group was given a different verb in the critical question. One group had the verb hit, the other had contacted, bumped, collided, smashed.

The mean estimated speed was calculated for each participant group. The verb contacted resulted in a mean of 31.8 mph, For the verb smashed, the mean was 40.5 mph

• the leading question biased the eyewitness’s recall of an event.

What is the definition of post-event discussion? (PED)

Occurs when there is more than one witness to an event. witnesses may discuss what they have seen with co-witnesses or with other people. This may influence the accuracy of each witness’s recall of the event.

Who performed an experiment to test post-event discussion?

Fiona gabbert et al (2003)

Outline the procedure.

Studied participants in pairs

• each participant watched a video of the same crime, but filmed from different points of view.

• This meant that each participant could see elements in the event that the other could not. E.g. only one of the participants could see the title of a book being carried by a young woman.

• Both participants then discussed what they had seen before individually completing a test of recall.

The researchers found that 71% of the participants mistakenly recalled aspects of the event that they did not see in the video but had picked up in the discussion. The corresponding figure in a control group, where there was no discussion, was 0%. This was evidence or memory conformity.

Why does post event discussion affect EWT?

One explanation is memory contamination. When co-witnesses to a crime discuss it with each other, their eyewitness testimonies may become altered or distorted.

• This is because they combine (mis) information from other witnesses with their own memories.

• Another explanation is memory conformity. Gabbert et al. concluded that witnesses often go along with each other, either to gain social approval or because they believe the other witness is right and they are wrong.

• unlike memory contamination, the actual memory is unchanged.

Evaluate the research on leading questions. (hint: real world application, evidence against substitution)

Real world application ✅

One strength of research into leading questions is practical uses in the criminal justice system.

• Loftus (1975) has presented evidence in court about the serious effects of leading questions on memory, which may lead to faulty convictions.

• Police officers need to be very careful about how they phrase their questions when interviewing eyewitnesses.

• Expert witnesses in court trials may explain the limits of EWT to juries.

• This shows that psychologists can help to improve the way that the legal system works.

Evidence against substitution ❌

one limitation of the substitution explanation is that EWT is more accurate for certain aspects of an event

• Sutherland and Hayne (2001) showed participants a video clip

• when later asked leading questions, participants’ recall was more accurate for the central details than for peripheral (secondary or minor importance) ones.

• Presumably participants’ attention was focused on central features and these memories were relatively resistant to leading questions.

This suggests that the original memories for central details were not distorted, an outcome that is not predicted by the substitution explanation.

Evaluate the research on post-event discussion (PED) (hint: research evidence and factors affecting post-event discussion)

Research evidence ✅

one strength is that PED may be the most powerful form of misleading information.

• Paterson and kemp (2006) showed participants a video of a crime, followed by different sources of misinformation (e.g. leading questions, false media reports and PED). A week later, participants were individually tested on their recall or the video.

• Results suggested that PED (even just hearing about other witnesses’ version of events) had the strongest influence on eyewitness memory.

This suggests that the effects of PED should be taken seriously during criminal investigations.

Factors affecting post-event discussion ❌

one limitation of PED is that its effects may depend upon the perceived credibility of the source.

• Skagerberg and Wright (2009) research involved 790 participants watching a crime video.

• participants were provided with additional information from a co-witness, and were than asked questions about the event.

• in each case, when information was supplied from a high credibility source (e.g. a police officer), participants’ testimonies were significantly more affected than if feedback was supplied from a low credibility source (e.g. child)

This suggests that the effects of PED should be taken seriously during criminal investigations.