Eye Witness Testimony (psych.)

• Interference: when 2 pieces of information are in conflict with each other.
• Proactive interference: old information interferes with new.

  e.g. teacher learns many names in the past and can't remember names of her current class.
• Retroactive interference: new information interferes with the old.

  e.g. you learned French for 2 years, then Italian for a year, when you meet up with a French speaking friend, Italian words keep coming out.
• 2 explanations:

  1. competition of response
  2. unlearning theory
• Competition of response: There is no actual loss of information, you're just accessing the wrong information in the memory. New information shifted old information. When you try to access it, it's moved somewhere else.
• Unlearning theory: New learning replaces old/previous learning.
• Factors affecting EWT:

  • Post event discussions: Gabbert et al. studied participants in pairs. Each participant watched a video of the same crime, but filmed from different point of view. This meant that each participant could see elements in the event that the other could not. For example, only one of the participants could see the title of a book being carried by a young woman.
  • Both participants then discussed what they had seen before individually completing a test of recall.
• EWT findings: Researcher found that 71% of the participants mistakenly recalled aspects of the event that they did not see in the video but had picked up in the discussion. The corresponding figure in a control group, where there was no discussion, was 0%.
• EWT: Gabbert et al concluded that witnesses often go along with each other, either to win social approval or because they believe the other witnesses are right and they are wrong. They call this phenomenon memory conformity.
• Memory contamination: When co-witnesses discuss a crime they mix information from their memories with other witnesses memories.
• Memory conformity: Witnesses go along with each other to win social approval or because they believe the other witnesses are right.
• Evidence challenging memory conformity:

  Hartmut Bodner et al (2009) found that effects of post-event discussions can be reduced if participants are warned of their impact. Recall was more accurate for those participants who were warned that anything they hear from a co-witness is second hand information (or 'hear say') and that they should forget it and recall only their own memory of the event.
• EWT demand characteristics:

  Laboratory studies have identified misleading information as a cause of inaccurate EWT, partly by being able to control variables. Maria and Michael (1989) argue that many answers given by participants in laboratory studies are due to demand characteristics. Participants usually want to be helpful and not let the researcher down. So they guess when they are asked a question that they don't know the answer to.
• Cues: Hints, pieces of information.
• Indirect cues like feel, smell.
• Loftus and Palmer: Researchers investigated whether the phrasing of questions influence judgement of speed. To test accuracy of EWT and leading questions.
• Experiment

  • Independent measures design.
  • 9 groups of 5 people, 45 students.
  • Critical question
  • 'How fast were the cars going when they () each other?'
• Experiment

  • Students were shown 7 films of traffic accidents.
  • The participants had to free recall the accidents, and complete a questionnaire.
  • Critical question.
• L&P results.

  Smashed: approx. 40 mph

  Contacted: approx. 30 mph
• L&P conclusion: The form of the question (leading question) can significantly affect the accuracy of an EWT answer.
• Leading questions: The response bias. Words of the question do not change the participants memory, only their response in the short-term.
• L&P more evidence:

  • 3 groups of 50 students.
  • 1 film of traffic accident.
  • Independent variable: verb in the question.
  • dependent variable: recollection of broken glass, estimate of speed.
  • one week later the participants return - forgotten their verb.
• 'Did you see any broken glass?'

  Smashed - 32% said yes.

  Hit - 14% said yes.

  Control grp - 12% said yes.
• Broken glass conclusion: Both pieces (the memory of the car crash and the verb) become one 'memory', this therefore means that leading questions can reduce the reliability of EWT.
• Weakness of Experiment 1 is that it lacks ecological validity.
• In the first experiment, 7 films of traffic accidents were shown, participants had to free recall and then complete a questionnaire with different verbs.
• The lack of ecological validity in Experiment 1 is due to the artificial setting, as when witnessing a car accident in real life, there are many distractions that could influence memory.
• Experiment 1 lacks ecological validity because it is expected for an accident to occur, unlike in real life where an accident is unexpected.
• EWT. WEAKNESS - UNGENERALISABLE. 


  Weakness is that the findings/results from the research is ungeneralisable to the rest of the population. In the first experiment, used 45 students, and in the second experiment used 150 students. Students haven't been driving for long, which can mean that they don't have knowledge to be judging the speed of the car, also they are more likely to be influenced by the verb in the critical q. The findings are ungeneralisable because they can't be repeated with older participants who have been driving for a while and have much more knowledge than students.
• EWT. STRENGTH - RELIABILITY.

  Strength is that the study has lots of standardised procedures. For example, they all had the same video clip, were in the same room, the participants had to free recall the accident and after they had to complete a questionnaire. Due to these controlled variables, the research can be replicated and gives reliable results.
• EWT. WEAKNESS - CAN BE ALTERED.

  Weakness is that the EWT can be altered. Kagerberg and Daniel showed their p's 2 clips. First clip had a mugger whose hair was dark brown, and in second clip the mugger had light brown hair. The p's discussed the clips in pairs, each saw diff. versions of the clips. Often didn't report what they had seen in the clip nor what they heard from the co-witnesses but a 'blend' of the 2 clips. Common answer wasn't light/dark brown but medium. This suggests that the memory itself is distorted through contamination by misleading PED, not results of memory conformity.
• EWT. WEAKNESS - EV.

  Weakness is there is low ecological validity. The setting was artificial, the participants are watching a crime clip. In real life, they wouldn't be able to pay attention to detail due to the emotional impact, in the artificial setting the participants are able to pay attention to detail and crime characteristics.
• EWT. STRENGTH - USEFULNESS.


  Strength is that research into EWT has been useful for the police when investigating crimes. The police have learned and now know the effects of memory contamination, so should split witnesses to reduce the memory contamination from PED. This is useful because then innocent people will not be put behind bars.