Factors affecting eye witness testimony
- the role of anxiety
- the role of schemas
- the age of the witness
- use of leading questions
- misleading information
- cognitive interview
The role of ANXIETY
Loftus:- Blood Stained Knife
found that participants were less likely to identify a man carrying a blood stained knife than the same man carrying a grease stained pen. This is because the witness was concentrating on the weapon, known as 'wepaon focus'
Loftus concluded that the fear or anxiety induced by the sight of the weapon narrows the focus of attention. accurate details of the scene, but less accurate recall of peripheral details.
Evaluation: ethical issues about the welfare of the participants (decived by the knife)
Anxiety: real life events
Yuille and Cutshall:-
They interviewed 13 witnesses to a real-life shooting involving the owner of the store and an armed thief. Some witnesses had seen the incident close up and some more distant.
The interviews showed that :-
- witnesses gave accurate accounts several months later
- those closest provided the most details
- misleading questions had no affect on accuracy
- those most distressed at the incident provided more accurate accounts -It appeared that anxiety enhanced the accuracy of EWT.
Another study is Christianson and Hubinette: 110 witnesses of a bank robbery. They concluded that people are more likely to remember highly stressful events if they occur in real life, rather than the artifical surroundings of a laboratory.
The role of schemas
DEF: Schemas are knowledge packages which are built up from our experiences. they enable us to make sense of familiar situations.
Cohen suggested ways in which schemas may lead to reconstructive memory:
- we store the central features of the event without storing the exact details.
- we can make sense of what we have seen by filling in missing info. eg. boy is running and a bus is pulling away fromt the bus stop, we assume he is running for the bus)
- we may use schemas as the basis for a correct guess.
We use stored knowledge and past experience to make sense of new information, because of this our memory of events can be reconstructed. this may account for some instances of inaccurate EWT.
Further experiment ...
Loftus and Plamer then conducted a second experiment:
Participants were shown a film containing a multiple car accident. then asked a question about speed only using 'hit' and 'smashed.' A week later participants were asked: 'did you see any broken glass?' Those in the smashed group were twice as likely to answer yes.
* This shows that misleading information did affect later recall.
- was conducted in the artificial surroundings of a lab and therefor lacks the emotional impact of real life.
Use of Leading Questions
DEF: a question that is worded in such a way that may bias how a respondent answers.
Loftus and Palmer: car accident
participants were shown a car accident and then asked: 'how fast were the cars going when they hit each other?' all participants were asked the same question but the word 'hit' was variously replaced with smashed, collided, bumped or contacted. Participants in the 'smashed' group reported the highest speeds.
*EWT was affected by misleading information, the different verbs used implied different speeds.
150 participants were shown a film of a car accident and then asked questions Group 1 - 'how fast was the car going when it passed the stop sign?' Group 2 - 'how fast was the car going when it passed the barn?' (Is NO barn) A week later group 2 were more likely to recall a barn (17%) than group 1 (3%) *showing that EWT is effected by misleading information
Stop and Yield Study:
Participants shown slides of a car stopping at a stop or yield sign, questions misled participants as to which sign they had been shown, money was also offered for the correct answer.
*on recall over 70% of participants still made an error
EVALUATIONS: of all studys
- Lab based studies lack ecological validity
- participants may alter what they say due to demand characteristics
- people are more accurate if allowed to answer 'not sure'
- people are more acccurate if asked questions in a logical order Bekerian and Bowers repeated the stop and yield study asking questions in a logical order, they found no affect from the misleading quesitons.