Lecture2 Eyewitness Memory_student-2 (1).pdf

Crime Investigations: Witnesses I Associate Professor Helen Paterson Phone: 9036 9403 Email: [email protected] The Plan… Background Estimator variables and system variables The misinformation effect The false/repressed memory debate Factors increasing susceptibility to the m...

Crime Investigations: Witnesses I Associate Professor Helen Paterson Phone: 9036 9403 Email: [email protected] The Plan… Background Estimator variables and system variables The misinformation effect The false/repressed memory debate Factors increasing susceptibility to the misinformation effect Limitations of research on the misinformation effect Learning Outcomes At the end of this lecture you will be able to:  Define estimator variables and system variables. Give examples of each and discuss how they influence memory.  Define the misinformation effect. Describe and critically evaluate research on it. Discuss factors that increase susceptibility to it.  Describe and critically evaluate research on rich false memories  Discuss the false/repressed memory debate Background Eyewitness testimony is commonly used as evidence in court and is one of the most persuasive forms of evidence for juries (Wells, Lindsay, & Ferguson, 1979). It is important to establish whether or not the juror’s faith in these testimonies is warranted. Many psychologists argue that eyewitness memory is not as reliable as the layperson may believe.  5-5 Background Eyewitness memory is typically assessed in two ways:  Recall Memory: Reporting details of previously witnessed event/person  Recognition Memory: Reporting whether what is currently being viewed/heard is the same as the previously witnessed person/event of interest (e.g., Identification evidence: Next class)  5-6 Estimator Variables and System Variables There are two types of factors that can affect eyewitness memory (Wells, 1978) 1. Estimator variables: Variables that are present at the time of the crime and cannot be changed 2. System variables: Variables that can be manipulated after the fact and impact the accuracy of witnesses Estimator Variables  Many features of an event can influence a person’s perception – Exposure time – Lighting – Distance – Physical disguise – Distraction Estimator Variables Witnesses can view the same thing and perceive it differently. Estimator Variables Expectations affect perception  We construct our memories partly on what we perceived at the time and partly on our expectations, beliefs, and current knowledge. Estimator Variables  E.g. Picture of Caucasian man holding razor blade talking to an African-American man (Allport & Postman, 1947) Estimator Variables Context can affect our perception of events Estimator Variables Own race bias  Tendency for people to have difficulty identifying people of another race – E.g., Platz & Hosch, 1988 – 86 convenience store clerks in El Paso, TX – Asked to identify 3 customers (confederates): Caucasian, African-American, and Latino – Results: More likely to identify same race customer Estimator Variables Own race bias  Likely due to a lack of interracial contact – own race bias NOT evident in a sample of avid and knowledgeable NBA fans who are Caucasian (Dunning et al., 1998) “Flashbulb memory”: Where were you when…? Estimator Variables Emotional Level Yerkes-Dodson law  Memory best at optimum level of arousal Yerkes & Dodson, 1908 Estimator Variables Easterbrook hypothesis (Easterbrook, 1959)  Highly aroused witnesses have better memory for central details than peripheral details Estimator Variables Weapons focus effect (Steblay, 1992)  Presence of a weapon draws attention and impairs a witness’ ability to identify a culprit Study (Loftus et al. 1987)  Slides of customers approaching tellers  Independent variable: gun or checkbook  Dependent variables: eye movement and accuracy of identifications  Results: When gun present, spent more time looking at it and less likely to identify person in a lineup 2. System Variables The delay between witnessing an event and giving a statement can affect memory System Variables Questioning techniques used by the police can affect eyewitness accuracy Misinformation effect: Exposure to incorrect information about an event after it has occurred often causes people to incorporate this misinformation into their memories Elizabeth Loftus, 1975 Misinformation Effect: Research (Loftus, 1975) Participants (Ps) saw pictures of an accident showing a Stop sign at an intersection. Some Ps were asked a leading question suggesting that there was a Give Way sign at the intersection. Participants were later shown 2 pictures – one with the car next to a Stop sign and one with the car next to a Give Way sign. Misinformation Effect: Research (Loftus, 1975) % Correct 80 60 40 20 0 Not Misled Misled When Ps were later tested on their memories for the event. Those exposed to the false information now believed that the Give Way sign was, in fact, part of the original accident scene. Misinformation Effect: Research (Loftus & Palmer, 1974) Ps shown a film of a traffic accident Ps asked “How fast were the cars going when they smashed into each other” gave higher speed estimates than those asked, “How fast were the cars going when they hit each other?” A week later, Ps in the smashed condition were more than twice as likely to recall broken glass when in fact there was none Speed Estimates: Miles / hour When Small Words Matter False Memory Research Loftus & Pickrell (1995): – Will people accept suggestions for “rich false memories”? – Gave students 4 short narratives of childhood experiences – Told participants: all 4 were provided by family members – 3 provided by family, 1 completely false False Memory Research – “Lost for an extended time in a shopping mall at age 6 and rescued by an elderly person” – First checked if recalled: vague or no memories – After several suggestive interviews, 25% reported being lost in a mall and gave rich and vivid details But… Being lost in a mall as a kid is pretty common! Maybe they were lost in a shopping mall and now remembered Same technique used to create memories of: – being hospitalised overnight – having an accident at a family wedding. – having nearly drowned but been rescued by a lifeguard – being the victim of a vicious animal attack False Memory Research (Wade et al, 2002) Participants shown falsified photographs of an event that had never occurred After several interviews, 50% of the Ps recalled, partially or clearly, the fictitious hot-air balloon ride False Memory Research (Braun et al, 2002) Participants were shown a fake print advertisement that described a visit to Disneyland and how they met and shook hands with Bugs Bunny. Later, 16% reported meeting and shaking hands with Bugs Bunny Repressed / False Memories Loftus believes that therapists sometimes implant false memories of sexual abuse in their patients. Others believe that the memories are for actual events, but they were repressed and later recovered Repressed / False Memories: Reported cases (Lipton, 1999) Reasons for increase in reported cases “Many women who were abused don't have memories, and some never get any. This doesn't mean that they weren't abused', and 'if you think you were abused, and your life shows the symptoms, then you were.” (The Courage to Heal by Bass & Davis, 1988) Celebrities reported repressed memories of childhood abuse Repressed Memories Do people bury traumatizing memories so deeply in their unconscious that they are unable to recall them until they are either spontaneously recalled or triggered by something? Repressed Memory Research Williams (1994) interviewed 129 women who had experienced well-documented cases of childhood sexual abuse on average about 17 years earlier. 38% of the women did not report any abuse during the interviews Goodman et al. (2003) conducted a similar study and found that 16% did not report any abuse Repressed memories? Reporting error? Too young to be aware of abuse? A New Solution? McNally and Geraerts (2009) offer an alternative to the two main perspectives (i.e., repression vs. false memories) They argue that some people don’t think of their abuse as traumatic at the time and they either fail to think about the abuse for years or forget their previous recollections until they spontaneously recall after encountering reminders outside of psychotherapy Implications of the misinformation effect Implications of the misinformation effect for credibility of eyewitness testimony:  When police officers or lawyers ask questions that are framed by what they believe happened, witnesses may incorporate incorrect information into their memory for the event  Police officers should ask open, non-leading questions Factors increasing susceptibility to the misinformation effect Age (young and old) Hypnosis Suggestibility Credible source of misinformation Repetition of misinformation Misinformation is peripheral Limitations of Research on the Misinformation Effect There is some controversy regarding the application of research on eyewitness issues to the courts:  Methodological Issues – Type of questioning – Ecological validity: Applicability of laboratory simulations to real life situations  Ethical Issues – Implanting false memories Take Home Message Eyewitness testimony is fallible and prone to mistakes Estimator variables are present at the time of the crime and cannot be changed System variables can be manipulated after the fact and impact the accuracy of witnesses Misinformation encountered through leading questioning can be incorporated into witness memory for the event. Controversy exists regarding the repressed memory/false memory debate.