WJEC A2 Psychology PY4 - Factors Affecting Eye Witness Testimonies

The 1976 Devlin Report = the Devlin Committee recommended in Britain, juries shouldn't convict on the strength of a single eyewitness testimony (EWT) alone. The New York Innocence Project estimates EWT is the single greatest cause of wrongful convictions (75%)

1. Weapon Focus

• one of main assumptions of the cognitive approach is that people have a limited capacity for processing info due to huge amount of info in the environment and would be impossible for a person to take in and process it all - therefore people are selective about what they take in
• cognitive system is equipped with an 'attentional filter' used to select some info and reject other info
• weapon focus effect is the tendency for witnesses of violent crimes to focus their attention on the weapon used; alleged to decrease other aspects of memory, particularly regarding identifying faces of criminals and resulting in poor quality testimonies 

EVALUATION

(+) Johnson and Scott (1976)

• pps sat outside of a room in which they overheard a conversation between 2 people; in condition 1, heard a hostile argument where one person walked out carrying a letter opener covered with blood; in condition 2, heard a harmless conversation followed by someone walking out of a room with an oily, greasy pen
• all pps were then given 50 photographs to identify person who walked out of room; Condition 1 = 33% could identify culprit whereas in Condition 2, 49% of pps could identify culprit
• because condition 1 pps had seen someone carrying a weapon (letter opener/knife), less able to recognise the carrier compared to someone with a non-weapon
• supports theory that weapon focus can lead to inaccurate identification of an individual and hinder precision of EWT

(+) Vrij (1998)

• pps approached by Vrij with syringe in hand, pps who were most frightened of injections recalled more details of hand/weapon and fewer of his face

• supports = weapon focus can lead individuals to concentrate on the weapon used, rather than face of weapon holder, leading to inaccurate identification of an offender
• also suggests it's not a weapon per se that is the cause of recall inaccuracy, but any stimuli we feel threatened by

(?) Pickel (1998)

• results from his study showed weapon focus was seen most in 'unusual' situations, not 'threat' situations, also WF seen in descriptions of offender, not line-up
• suggests it's unusualness of weapon in context rather than threat that causes poor recall associated with weapon focus

(-) Christianson et al (1993) survey of:

• 110 witnesses to 22 real armed bank robberies; bystanders or threatened tellers
• tellers had higher accurate recall than bystanders despite both faced with weapon
• refutes idea weapon focus can make EWT less accurate and hinder recall for 'real witnesses'; also refutes idea that emotional anxiety causes poor recall as tellers would have experienced greater anxiety yet had more detailed memory

2. Role of Emotional Arousal/Stress

• according to the Yerkes-Dodson Law and the Curve, an increase in arousal improves performance (efficiency of memory) but only up to a point (the optimal level) - once arousal has passed a critical point, performances tends to decline

EVALUATION

(+) Clifford and Scott (1978)

• showed pps one of two films involving same people, in one film = physical assault
• pps who viewed this film less likely to identify people involved than those who viewed the non-violent film
• appears witnesses to violent incidents generally recall less than witnesses to non-violent incidents, regardless of whether weapon was used or not
• BUT although this supports the Yerkes-Dodson Curve, the curve itself is unfalsifiable as not quantifiable because it doesn't identify levels of arousal

(+) Clifford and Hollin (1981)

• examined relationship between level of violence and recall; found that the higher the level of violence depicted, the poorer the participants' recall of an assault
• supports Yerkes-Dodson Curve and links to biological reasons that violent incidents increase activity and autonomic nervous system arousal, which has a detrimental effect on memory generally

3. Interference Effects - Leading Questions

• leading qs can influence recall by implying the answer, showing that suggestion by the power of language can extensively alter what we remember after an event

EVALUATION

(+) Loftus and Palmer (1974)

• conducted expt to see if leading qs can affect pps' estimate of speed
• found when using word 'smashed', led to 10mph higher estimated speed when compared with 'contacted', suggests leading qs can affect EWT

(+) Loftus and Zanni (1975)

• pps shown clip of car accident, 1 group asked: "Did you see A broken headlight?" and other asked "Did you see THE broken headlight?"
• 7% of "a" reported seeing broken headlight, 17% of "the" reported seeing it
• study supports memory can be changed by asking leading qs, potentially supplies misleading info, distorting original memory and replaced with inaccurate one

(+) Loftus (1979)

• offered $25 if recalled event accurately (given leading qs) and found this incentive did not prevent recall from being affected by leading qs
• concluded that if original memory had been intact, offer of money would have prevented influence of leading qs, therefore original memory reconstructed and permanently changed because of influence of leading qs

(-) Loftus (1979)

• conducted study where pps shown film of man stealing red wallet - 98% immediately recalled colour was red
• later read account describing wallet as brown but when asked to recall details of film again, only 2 pps changed original account from red to brown
• demonstrating that where misleading info is blatantly incorrect and involves central details, accuracy of EWT is not negatively affected, suggested EWT is not always distorted by leading qs

(-) Yuille and Cutshall (1986)

• thief tried to steal guns and money but was shot 6 times and died, police interviewed witnesses and 13 re-interviewed 4 months later
• recall found to be accurate even after a long time and 2 leading qs inserted by research team had no effect
• showed 13 witnesses of real life shooting (compared to expts on leading qs done in artificial environment) had remarkably accurate memories of a stressful event including weapons
• suggests in perhaps very stressful situations, leading qs don't affect someone's recall of an event, weakens theory on leading qs and suggests artificial laboratory studies of EWT lack ecological validity