EWT - Experiments

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Loftus et al - Anxiety

Tested how anxiety affects EWT and the weapon focus effect

Method

  • Had two seperate groups of Pps for two different conditions
  • Pps thought they were there for another experiment and were asked to stand outside and wait for it to begin
  • Whilst outside all Pps overheard a discussion in an ajoining room and then afterwards saw a man appear from the room, but in condition:
    • 1 - a man appeared greasy and holding a pen
    • 2 - the discussion was heated and a man appeared covered in blood with a bloody knife
  • Pps were then debriefed and asked to select the man they say from a selection of 50 photos

Findings

  • Pps in condition 1 were 49% accurate - Pps in condition 2 were 33% accurate
  • Pps in condition 2 were focused more on the weapon and more anxious
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Christianson + Hubinette - Anxiety

Investigating how emotional arousal affects EWT

What they did

  • Questioned 58 witnesses of real bank robberies
  • Some were bystanders - less emotionally aroused
  • Some were directly threatened by the robbers in some way - more emotionally aroused
  • Questioned on their recall of events and compared these to the CTV footage retained

Findings

The witnesses which were more emotionally aroused gave a more accurate recall of events. This was true even 15 months later

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Deffenbacher - Anxiety

  • Carried out a meta-analysis of 21 studies which had researched the effect of anxiety on EWT
  • His research supported the theory that high levels of anxiety cause inaccurate recall in EWT
  • He also found that high levels of anxiety had an effect on EWT of adults but not children

However, he explained the contradicting evidence given by other studies such as Christiansan and Hubinette, by referring to the Yerkes-Dodson LawThis states that low levels and high levels of anxiety are bad for recalling events accurately, but that medium levels of anxiety improve EWT recall. This theory is described as being curvilinear

(http://changingminds.org/images/yerkes.jpg)

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Loftus and Palmer - Misleading Information - 1

Testing to see if misleading information distorted accuracy of immediate EWT

Method

  • 45 students split into 5 groups were shown 7 different traffic accidents and after each were given a quick questionnaire
  • There was a critical question - 'About how fast did they hit each other?'
  • One group had the word 'hit' in the question, the other five either had:
    • smashed
    • collided
    • bumped
    • contacted

Findings

  • The group given the word 'smashed' gave a higher estimated speed (40) than the group given the word 'hit' (31)
  • This suggested that the form of questioning can have a significant effect on EWT
  • Post-event information can permanently distort a memory before it is stored
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Loftus and Palmer - Misleading Information - 2

Testing to see whether EWT could be altered by misleading post-event information

Method

  • A new set of Pps were divided in three groups and shown a video of a car accident
  • Afterwards group one were asked 'about how fast were they travelling when they hit?'
  • Group two were asked 'about how fast were they travelling when they smashed?'
  • Group three were not asked a question on speed (control group)
  • One week the students returned and were asked 'Did you see any broken glass?' when there was none

Findings

  • The first part of the experiment gave the same results as the first experiment - smashed gave higher speed
  • But the question asked a week later gave the results that Pps asked the speed question with smashed in repoerted more times seeing glass than the Pps asked the question containing hit - but overall more people said no in all groups
  • This suggests misleading post-event information does distort memory
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Parker & Carranza - Age

Compared ability of immediate recall between primary school children to college students

Method

  • Showed all Pps a series of slides of a mock crime
  • Afterwards they were asked to identify a target in the slides from a selection of photos

Findings

  • Children were more likely to give an answer than the college students but were no more accurate
  • Children are influenced by authoritive figures and wanted to please them by giving an answer
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Yarmey - Age

Compared short recall ability between young, medium and old aged witnesses

Method

  • Approached 625 random people on the street in a city after they had been approached by a woman they had talked to who had asked for directions two minutes before
  • They were asked to recall the physical characteristics of the woman

Findings

  • Younger witnesses were more conident in their recall than older witnesses but were no more accurate
  • This could mean that younger witnesses will sound more believable in court and be more influential even if they are not more accurate
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Memon - Age

Compared the accuracy of recall between young/medium aged witnesses and old witnesses

Method

  • Asked Pps in both conditions to identify a target 35mins after the incident from a selection of photos
  • They then asked Pps to identify a target one week after the incident from a selection of photos

FIndings

  • After a 35min delay there was no significant difference in recall between the young and the old witnesses
  • After a one week delay the older witnesses were significantly less accurate in their identification
  • The longer delay is much more realistic and reflects EWT in real situations, so older witnesses could be less reliable witnesses
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