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Eyewitness Memory

Eyewitness Memory. Dr. Anne Cybenko University of Dayton Research Institute. “The Innocents” Taryn Simon. Why do People Care?. There have been 289 exonerations in the US www.innocenceproject.org Over 70% of those have been due at least in part to a mistaken identification

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Eyewitness Memory

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  1. Eyewitness Memory Dr. Anne Cybenko University of Dayton Research Institute

  2. “The Innocents” Taryn Simon

  3. Why do People Care? • There have been 289 exonerations in the US • www.innocenceproject.org • Over 70% of those have been due at least in part to a mistaken identification • It’s a unique situation that tests human memory and decision making

  4. Ronald Cotton Picking Cotton CORRECT IDENTIFICATION FALSE IDENTIFICATION

  5. The Basics: What Happens when there’s a witness to a crime? • This guy commits a crime and someone witnesses it.

  6. The Basics: What Happens when there’s a witness to a crime? • Police get a description from the witness He was about 6’ tall, brown hair, brown eyes, no facial hair…

  7. The Basics: What Happens when there’s a witness to a crime? • Police find a suspect who may be: Guilty or Innocent

  8. The Basics: What Happens when there’s a witness to a crime? • Witness is shown a lineup that is either Perpetrator Present Perpetrator Absent

  9. The Basics: Possible Outcomes of a Lineup Type of Lineup Witness’s Decision

  10. How is it studied? • Mostly undergraduate participants • Participants watch a mock crime (video or live) • Participants usually give a description • Filler task • Presented with a lineup • Make an Identification

  11. What Exactly do People Study • Witness interview techniques • Child interview techniques • Showups • Foil selection • Lineup Presentation • Lineup Instructions • Multi-modality lineups • Double-blind lineups

  12. Topics for today • Simultaneous or Sequential Lineups • Accuracy and Response Time • Verbal Overshadowing Effect • Interference Theory

  13. Sequential vs. Simultaneous Lineups

  14. I am going to show you six photographs. Please look at all six photographs before making any comment. The person who committed the crime may or may not be among those shown in the photographs you are about to see. If you recognize any of the persons in the photographs as the suspect, go back and pick out the person you recognize. If you recognize any of the persons please do not ask me whether your choice was ‘right’ or ‘wrong’, as I am prohibited by law from telling you.

  15. SAN BERNARDINO COUNTY SHERIFF PHOTO LINE-UP 1 2 3 4 6 5

  16. I am going to show you some photographs. The person who committed the crime may or may not be among those shown in the photographs you are about to see. If you recognize any of the persons in the photographs as the suspect, please tell me and we will stop the lineup. If you recognize any of the persons please do not ask me whether your choice was ‘right’ or ‘wrong’, as I am prohibited by law from telling you.

  17. SAN BERNARDINO COUNTY SHERIFF PHOTO LINE-UP

  18. SAN BERNARDINO COUNTY SHERIFF PHOTO LINE-UP

  19. SAN BERNARDINO COUNTY SHERIFF PHOTO LINE-UP

  20. SAN BERNARDINO COUNTY SHERIFF PHOTO LINE-UP

  21. SAN BERNARDINO COUNTY SHERIFF PHOTO LINE-UP

  22. SAN BERNARDINO COUNTY SHERIFF PHOTO LINE-UP

  23. Sequential vs. Simultaneous Lineups Lindsay & Wells (1985)

  24. Sequential vs. Simultaneous Lineups • Results depend on: • Similarity of the innocent suspect to the perpetrator • Innocent suspect position in the sequential lineup • (Clark & Davey, 2001)

  25. Innocent suspect is high similarity to perpetrator Innocent suspect is medium similarity to perpetrator

  26. Sequential vs. Simultaneous Lineups • The Mecklenburg Report (2006)

  27. Sequential vs. Simultaneous Lineups • Absolute vs relative decision making

  28. Model-Based Predictions • WITNESS model (Clark, 2003) to generate predictions • Perpetrator is represented as a vector of features, P. • Memory of the perpetrator (M): • Feature j of P is stored correctly in M with probability a. • Feature j of P is stored incorrectly in M with probability 1 – a. • Innocent suspect and foils: • Feature j matches the perpetrator with probability s • Feature j mismatches the perpetrator with probability 1 – s. • Match each lineup member to memory (M). • m(L1,M), m(L2,M), … , m(L6,M) (for six person lineup) • Apply decision rule to make a decision.

  29. WITNESS model • Best Above Criterion (BAC): A witness identifies the best matching lineup member if the match to memory is above criterion. (Absolute judgment) • Relative Difference Model (RD): Best matching lineup member is identified if the difference between the best match and the next-best match is above a difference criterion. (Relative judgment)

  30. Accuracy and Response Time • Dunning & Perretta (2002) • Four eyewitness studies using a combination of videotaped and live crimes. Measured response time and accuracy

  31. Accuracy and Response Time • Witnesses making their ID’s faster than 10-12 seconds were nearly 90% accurate • Witnesses that took longer than 12 seconds were 50% accurate • Automatic vs Deliberative processes * p<.05 ** p<.01 Study 1 participants had think aloud task

  32. Accuracy and Response Time • Optimal response time changes with: • An increase in retention interval (Brewer et al., 2006) • An increase in the size of the lineup(Brewer et al., 2006) • Confidence of the witness (Weber et al., 2004) • Age (Weber et al., 2004)

  33. Verbal Overshadowing Effect • Verbalizing the appearance of previously seen visual stimuli impaired subsequent recognition performance

  34. Schooler & Engstler-Schooler (1990) • Experiment 1 • Does describing a perpetrator affect ones ability to identify him?

  35. Schooler & Engstler-Schooler (1990) • Experiment 3 • Do these results apply to all stimuli that are difficult to describe?

  36. Schooler & Engstler-Schooler (1990) • Experiment 5 • Does this pattern of results change if there’s a limited amount of time to ID the suspect?

  37. Meissner & Brigham (2001) • Meta-analysis on 29 published and unpublished verbal overshadowing studies • Zr = -.12, a small but significant negative effect of verbal overshadowing

  38. Studies that don’t find verbal overshadowing • Long delay between description and ID (Finger & Pezdek, 1999) • More than 1 trial (Fallshore & Schooler, 1995; Houser et al., 1997; Melcher & Schooler, 1995) • Following re-presentation of visual stimulus (Schooler et al., 1996) • When a cognitive interview is used (Finger & Pezdek, 1999; Meissner et al., 2001)

  39. Possible Mechanisms • Availability assumption • Visual representation remains available in memory despite the temporary verbal impairment • Modality mismatch hypothesis • Competing representations in memory from different modalities

  40. Types of Interference • Proactive interference: When information that is presented BEFORE a target event interferes with the memory for that target event • Retroactive interference: When information that is presented AFTER a target event interferes with the memory for that target event • Retroactive interference is stronger than proactive interference (Schemeidler, 1939; McGeoch and Underwood,1943; Melton and Von Lacrum, 1941)

  41. Hypotheses of Interference • Changed-trace hypothesis: Outside information interferes with target information because it changes the memory trace of the target information. • Multiple-trace hypothesis: Outside information interferes with target information because it creates a separate memory trace that is recalled instead of the target trace.

  42. McCloskey & Zaragoza (1985) • Argued that the Loftus et al. results could have been due to 2 other issues: • Original stimulus never encoded • Remembered both, trusted/responded with the one from the narrative

  43. McCloskey & Zaragoza (1985) • Participants were presented with slides depicting a maintenance man enter an office, fix a chair, then steal $20. • 4 Critical items within the slides • tool (hammer, wrench, or screwdriver) • soda can (Coke, 7-up, or Sunkist) • coffee jar (Folgers, Maxwell House, or Nescafe) • magazine (Glamour, Vogue, or Mademoiselle) • Participants presented with written account of what they just saw. This written account contained misinformation for 2 of the items.

  44. McCloskey & Zaragoza (1985) • Two types of tests: • Traditional Recognition Test: Target vs. Interfering • Saw Coke, read about 7-up, Test: Coke or 7-up • Modified Recognition Test: Target vs. Novel • Saw Coke, read about 7-up, Test: Coke or Sunkist • Traditional Recognition test – Picked 7-up • Modified Recognition test – Picked Coke • Participants could not have picked Coke in the modified test if reading about 7-up changed their memory trace

  45. Zaragoza, McCloskey, and Jamis (1987) • Replicated McCloskey and Zaragoza (1985) with 2 changes • Gave either incorrect or neutral information in the recap of the slides (“7-up” or “soda” ) • Test was in the form of open ended questions: “The key to the desk was next to a ____ can?” • participants performed equally well on the recall tests • If the misinformation really changed the memory trace, participants should have performed considerably worse on the recall test for the misinformation items.

  46. Tversky & Tuchin (1989)Belli (1989) • Replicated McCloskey and Zaragoza’s (1985) experiment • Testing was in the form of Yes/No statements: “Below the magazine rack there was a copy of Vogue magazine.” • Tversky and Tuchin asked about the critical item (the one from the slides), the misinformation item (the one from the summary of the slides), and the novel item (the one that did not appear at all) • Belli asked about the critical item, and the novel item. • Misleading postevent information reduced the "Yes" responses to the question about the original item. • T & T Subjects were equally good at rejecting the novel item • T & T Similar number of subjects responded yes to original item as responded yes to the misleading item. • Belli - misled subjects were better than control subjects at rejecting the novel item • Belli concluded memory trace was changed, T & T did not.

  47. Chandler (1989 & 1991) • McCloskey and Zaragoza’s results could have been a product of their stimuli having too many unique discernable features such that even if the trace was altered, some of those features would remain unchanged. • Used stimuli that were very similar to each other. • Conducted 10 Experiments

  48. Chandler - Stimuli • Nature photographs • Cut in thirds A A’ A”

  49. Chandler’s Methodology • Variables between experiments: • Proactive or Retroactive interference • Presentation time • Retention interval • Number of stimuli

  50. Chandler’s Methodology (Retroactive Interference) Target List Interfering List Test Retention

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