Eye Witness Testimony and Limitations Flashcards
Wagenaar and Groeneweg (1990) - Prisoners Camp Erica
Compared testimonies given in 1940s and 1980s by prisoners in Camp Erika.
Essential details were forgotten, e.g. imprisonment dates, instances of maltreatment, names and appearance of torturers, and forgetting seeing a murder.
Crundall and Underwood (2000) - Car Drivers
After two weeks - car drivers recalled only 20% of the accidents and near-misses that they had originally recorded experiencing during that time.
Why is eyewitness testimony so error-prone?
7 Reasons
- Poor view of events and their perpetrators.
- May not appreciate events’ significance at the time (e.g., con-man).
- Changes in the suspect’s appearance (e.g. disguises).
- Effects of witnesses’ stress/arousal:
“weapon focus” (e.g. Christianson and Loftus 1991). - Elapsed time since event was witnessed.
- Effects of post-event information (e.g., witnesses’ own ruminations; listening to other people’s accounts of it; misinformation).
- Effects of expectations and schemas (both on initial encoding and subsequent memory).
- Weak relationship between witnesses’ accuracy and confidence.
Wells and Olson (2003): Review factors affecting eyewitness performance.
System variables - under control of legal system (e.g. interview procedures, lineup presentation modes, etc.)
Estimator variables - not under control of legal system (e.g. sex and age of witnesses, lighting conditions at time of crime, etc.)
Little evidence of effects of witness’ sex and intelligence.
Effects of age, event duration, stress/arousal, cross-race identifications.
Can we distinguish good witnesses from bad?
Bindemann, Brown, Koyas and Russ (2012):
Video of a staged theft followed by a lineup (either TP or TA).
Followed by 1-in-10 face identification test (40 trials, half TP).
Overall identification performance was poor. (TP expt 1: 22% correct identifications; TP expt. 2: 18%).
For choosers, correlation between lineup and face identification test performance (r = .70).
Darling, Martin, Hellmann and Memon (2009):
Measured individual differences in response to Navon letters.
Video of a staged bank robbery followed by a simultaneous (TP) lineup.
High susceptibility to global interference when reporting small letters was associated with better eyewitness identification performance - individuals with strong “global” processing bias might be better witnesses than ones with “local” bias.
Exposure time and delay: MacLin, MacLin and Malpass (2001) review:
Increased exposure time usually improves recognition accuracy, reduces false identifications.
Increased delay usually decreases recognition accuracy, increases false identifications.
Exposure time and delay: Bahrick, Bahrick and Wittlinger (1975) and Read (1995)
Little effect of delay on familiar face recognition (e.g. schoolmates).
Increased exposure time can decrease performance by increasing witnesses’ readiness to make false identifications (confuse increased familiarity due to contextual information, with increased familiarity from perceptual knowledge).
Effects of expectations and schemas: Allport and Postman (1947):
Picture of a black man, and a white man holding knife.
Participants tended to recall that it was the black man holding the knife.
Effects of expectations and schemas :Neisser (1981):
James Dean and Watergate testimony: memory for gist, but inaccurate about temporal order of events, who said what to whom, precisely what was said, etc.
Effects of stress and arousal:
- Yerkes-Dodson “Law” (1908): U-shaped relationship
- Easterbrook (1959): cue utilisation theory
- Steblay (1992): weapon focus
- Christianson (1992): effect of stress
1) inverted U-shaped relationship between stress/arousal and performance.
2) cue utilisation hypothesis: stress narrows attention to central items at expense of peripheral ones.
3) “Weapon focus” effect: decreased recognition due to presence of a weapon.
4) effects of stress are an interaction between stress level and many other factors.
Effects of stress and arousal (Part 2
- Peters (1988): Effects of stress on face recognition
- Yuille and Cutshall (1986): 13 witnesses of violent crime
- Odinot, Wolters and Koppen (2009): Supermarket Robbery
1) Effects of stress on face recognition.
Memory for face of nurse and aide during immunisation.
Pulse rate higher for nurse than aide.
Aide identified better than nurse, from target-present lineup.
2) Study of recall by 13 witnesses of a violent crime.
Accurate memories for events 4-5 months later.
Reported stress level at time of crime not significantly related to subsequent recall. But higher-stress witnesses also closer and more involved in the crime.
3) 84% of recalled information was correct.
Items provided in free recall were more accurate than items produced by specific questions (90% vs 78%).
Large individual differences in accuracy (75% to 97%).
Are experiments on the effects of stress ecologically valid?- - Deffenbacher, Bornstein, Penrod and McGorty (2004):
- Morgan et al (2004):
1) Real crimes likely to produce defensive responses,
Lab studies likely to produce orienting responses.
Consequence: lab studies may underestimate impairment of eyewitness performance by stress.
2) Overall, positive identifications of interrogators were higher in the low-stress condition, and false positives were lower.
Large individual differences in ID performance:
42-45% unaffected by stress
42-50% worse when stressed
8-13% better when stressed.
Influences of witnesses on each other - “memory conformity”:
- Wright, Self and Justice (2000): storybook
- Gabbert, Memon and Bull (2003): Different thefts viewed.
1) Pairs were unaware they had seen different versions of a storybook (present or absent “accomplice” to a crime). Discussion produced conformity in pairs’ responses.
2) Pairs saw different videos of a “theft”.
60% of those who had not seen the crime came to believe it had occurred;
30% who had seen it came to believe it had not occurred.
Why do memory conformity effects occur?: Three types of influence
Informational influence:
Witness regards other witness’ memory as more reliable than their own.Faulty source monitoring:
Remember the information, but not who supplied it.
Normative influence:
Witness tries to present themselves favourably to the other witness.:
