factors affecting eyewitness testimony Flashcards
(43 cards)
summarise anxiety on EWT?
- anxiety= has strong emotional and physical effects (which can be triggered by stressful events) and can negatively effect accuracy of EWT —> research shows possibilities that recall may actually be better in presence of high anxiety
what negative effect may occur due to anxiety on recall/acciracy?
Weapon focus effect (WFE)
what is weapon focus affect (negative effect of anxiety) and why is it bad?
- tends to happen during commission of crime in which a weapon is used
—> eyewitnesses may fixate on weapon due to fear/flight or fight response etc
—> due to intense focus on weapon = person wielding it isn’t really noticed (eyewitness does not take in their height, hair colour etc)= recall of details of perpetrator = virtually non-existent or recall of any other details of the event
who did research on the weapon focus effect?
Johnson and Scott 1976
research on WFE procedure and findings
- ppts told they were taking part in a lab study and asked to sit down in waiting area —> ppts split into low and high anxiety group —> while ppts waiting in waiting area:
- low anxiety grp overheard casual convo from a room and saw a man walk out with a pen and grease on his hands
- high anxiety group overheard an argument from the room and saw a man walk out with a knife and blood on his hands
—> ppts asked to identify the man from a set of 50 photos
Findings
- low anxiety group = correctly identified the man (mean accuracy 49%)
- high anxiety grp = accuracy 33%
—> concluded anxiety focuses attention on the weapon and away from other details of the event. Tunnel theory of memory= ppl have enhanced memory for central events
why may anxiety have positive effects on EWT accuracy and recall?
- may be due to an increase in hormone adrenaline which triggers fight or flight response or freeze= high state of alertness
who carried out research into positive effects of anxiety on EWT accuracy/recall?
Yuville and Catshell 1986
research into positive effects of anxiety on EWT procedure and findings?
- witnesses of a real life crime shooting (in Canada where shop owner shot a theif dead)= asked to participate (13 witnesses)
- ppts were interviewed 4-5 months post shooting —> interviews were compared to police interviews at original time of shooting
- accuracy = measured by number of matching details in each interview
- ppts asked to rate their stress levels at time of incident (7 point scale) and related issues e.g. insomnia
Findings:
- witness recall= accurate as events recalled 4-5 months later matched original police reports
- witnesses who resorted high stress at time of incidence = most accurate recall (88%)
- low stres = 75% accuracy
—> suggests anxiety doesn’t have negative effect on recall if events (accuracy, it may actually enhance it)
what is the explanation for contradictory findings
Yerkes and Dodson 1908 proposed tehres a relationship between arousal (emotional state) and performance
—> called Yerkes-Dodson law (as well as inverted U theory) + can explain contradictory findings related to accuracy of EWT
(see diagram on mind map)
explain The U theory (related to contradictory findings of EWT.
- when crime is witnessed, a person becomes emotionally (anxiety) and physiologically (adrenaline release) aroused
- low levels of arousal (anxiety) = associated with low levels of performance (recall and accuracy in EWT)
- as arousal increases performance increases up to an optimum
- after this point if arousal continues to increase = performance starts to decrease
anxiety affecting EWT eval - 1
Johnson and Scott may not have studied anxiety
—> oops may have looked at weapon because they were surprised not scared
—> Pickel 1998 did research using unusual objects (chicken, scissors etc) —> found EWT less accurate when unusual objects are involved —> suggests weapon focus effect = due to surprise rather than anxiety
ALSO
Johnson and Scott study= unethical (deception etc) + lacks ecological validity = demand characteristic etc
anxiety affecting EWT eval 2
study support idea that anxiety leads to less accurate recall
—> Valentine and Mesolithic (2009) found ppts recall of actors in London Dungeons = less accurate with high compared to low anxiety
—> study = used objective measure of heart rate to measure anxiety = high validity and supports WFE
anxiety affecting EWT eval 3
study support the idea that anxiety leads to higher accuracy of EWT
—> Christionsan and Hubriette 1993= found higher recall in witnesses of a real life bank robbery —> victims of robbery (high anxiety) had better recall of the details of tiggers compared to bystanders (low anxiety)
—> supports Yuille and Cutshall
BUT both these researches used a real life context and crime as part of investigation= invalidates findings due to lack of control over confounding variables which could influence recall and accuracy of EWT e.g. post event discussions
anxiety affecting EWT eval 4
- Yerkes Dodson law / inverted U theory= doesn’t account all factors contributing to anxiety e.g. cognition, emotion state, physical health which could affect accuracy of EWT
—> Yerkes Dodson law = too simple
anxiety affecting EWT eval 5
- most research takes a nomothetic approach = problematic as small sample which can’t generalise to everyone
what is eyewitness testimony?
ability of someone to remember details of events e.g. crimes, accidents which they have observed
what is misleading information?
incorrect info given to an eyewitness after an event
what are leading questions?
questions that are worded which may suggest a certain answer or lead you to give a certain answer
why is it vital to not use leading questions in EWT?
cause they could affect memory of eyewitness and accuracy of their testimony
- they’re a form of misleading info as can prompt eyewitnesses to recall events incorrectly —> response bias
what does the substitution explanation propose about leading questions?
- they change a persons memory of an event by adding detail that wasn’t present at time of witnessing the event
who did research into leading questions on eyewitness recall?
Loftus and Palmer 1974
example of a leading question?
‘Did you see the knife?’= leading
should use ‘Did you see a knife?’
what was Loftus and Palmer procedure? (experiment 1)
- 45 student ppts (split into 5 groups) were shown films of car traffic accidents
- after films each group given questionnaire to complete which included critical questions in which the verb used to describe the car accident was changed:
‘How fast was the car travelling when it (verb) the other car?’
Verbs= hit, contacted, smashed, collided, bumped - each group had different verb as part of questionnaire and each verb constituted 1 condition of the independent variable
Loftus and Palmer findings (experiment 1)?
dependent variable was measure as estimated speed in MPH
-> verb ‘contacted’ resulted in lowest mean of speed 31.8MPH and verb ‘smashed’ mean was 40.8 MPH
—> leading questions biased eyewitnesses recall of event —> response bias
