Yellowstone Mystery Who did it Eyewitness Memories

1
Yellowstone MysteryWho did it? Eyewitness
Memories

• Developed by Maggie Renken
• University of Wyoming
• Fall 2007

2
Part 1

• Eyewitness Memory

3
I know that face!

• Face-recognition rates are usually around 90

Wow! Thats extremely high!
So eyewitness memory must be pretty
accurateright?
No, this 90 accuracy rate does not apply to a
criminals face
4
Why isnt eyewitness memory very accurate?

• Witness Factors
• Age
• Exposure Duration
• Race
• Confidence
• Reaction Time
• Weapon Focus

• System Variables
• Verbal Overshadowing
• Lineup
• Post event information
• Post-identification feedback

5
Witness factor Age

• Children are unreliable witnesses
• Adults over 60 are more
• likely to make false identifications

6
Witness Factor Exposure Duration

• The longer the exposurethe more accurate the
  identification
• BUT
• the longer the exposure,
• the more confident
• the witness,
• even if wrong

7
Witness Factor Race

• Better at recognizing own-race faces
• Recognize own-race faces holistically rather than
  by features
• Holistic recognition comes from experience with
  or exposure to other races

8
Witness Factor Confidence

• Confidence is a weak predictor of eyewitness
  accuracy
• Confidence ? Accuracy

9
Witness Factor Reaction Time

• If an eyewitness comes to a decision within a
  10-12 second window, they are more likely to be
  accurate
• In combination with confidence, 90 accurate

10
Witness Factor Weapon Focus

• A witness confronted with a weapon tends to focus
  on the weapon rather than the perpetrators face.
• Flashbulb memory
• Challenger Study
• High arousal did not lead to better memory

11
Yerkes-Dodson LawArousal Memory
Performance
low
moderate
high
Emotional Arousal
12
System Variable Verbal Overshadowing

• Verbally describing a face can impair future
  attempts to identify the face
• Individuals who first described a face were 1.27
  times more likely to misidentify the face from a
  lineup

13
System Variable Lineup Fairness

• People in the lineup should be selected based on
  similarity to the perpetrator
• No individual should stand out in the lineup
• The interviewer should not favor any individual
  in the lineup

14
System Variable Lineup Presentation Mode

• Conventional Simultaneous Parade
• All faces presented at the same time
• Fosters a relative judgment strategy
• Sequential Lineup
• Faces presented one at a time
• Absolute yes or no for each face

15
System Variable Post event information

• Information given to the eyewitness after the
  event occurs
• Loftus Palmer (1974)
• Does post-event information
• alter memory for the original event?
• Background
• Humans are not good at estimating numerical
  quantities (time, speed, distance, angle)

16
Loftus Palmer (1974) Procedure

• How fast were the vehicles
• going when they
• Group 1 smashed into each other?
• Group 2 collided?
• Group 3 bumped into each other?
• Group 4 hit each other?
• Group 5 contacted?

17
Loftus Palmer (1974) Results
18
Loftus Palmer (1974) Conclusion

• Post-event leading questions
• clearly influence memory for the original event.
• can bias numerical estimates.
• Original information and post-information are
  integrated into a single memory
• People no longer discriminate between original
  and post-event information.

19
System Variable Post Identification Feedback

• Information that is conveyed to the
• eyewitness after he or she identified
• a perpetrator from a lineup

20
Wells Bradfield (1998)

• Participants watched a brief clip of a crime
• Then, they picked a suspect from a photospread
• The suspect wasnt present
• Some were given confirming feedback
• Good, you identified the suspect
• Confirmation increased certainty, self-reports of
  viewing quality, memory clarity, speed of
  identification.

21
Effects on Confidence
11-12 years old
(Hafstad, Memon, Logie, 2004)
22
Effects on Clarity of Memory
23
Interpretation of Effects

• Could this be hindsight bias?
• Told the correct answer, witness assumes they
  knew it all along?
• Is the post-id feedback effect similar to the
  post-event misinformation effect?

24
Part 2

• How Memory Works

25
What is memory?

• Memory
• the persistence of learning over time through
  the storage and retrieval of information

26
Information Processing

• Encoding
• We get info into our brain
• Storage
• We keep that information
• Retrieval
• We get it back out later

27
Model of Memory
External events
storage
Sensory memory
Long-term memory
Short-term memory
encoding
retrieval
28
Working Memory

• Processing images and words at the same time

29
Interesting Memory Phenomena

• The next-in-line effect
• Learning right before sleep
• Learning during sleep

30
The rioter threw?

• Our memory system processes info not just by
  repetitive rehearsal but also by coding its
  significant features
• We remember what we encoded, not necessarily
  exactly what happened

31
Encoding Verbal Info

• Semantic encoding (meaning)
• Acoustic encoding (sound)
• Visual encoding (images)
• Information encoded semantically is more easily
  retrieved because it is processed at a deeper
  level.

32
Encoding Imagery

• Computer
• Empty
• Bicycle
• Inherent
• Fire
• Behavior

33
Storing Memories

• Sensory memory
• Information first enters the memory system
  through the senses. We register and briefly store
  visual images and sounds
• Short-term memory
• The span for information just presented is very
  limited--a seconds-long retention of up to about
  seven items, depending on the info and how it is
  presented
• Long-term memory
• Our capacity for storing information permanently
  is essentially unlimited

34
Storing Memories in the Brain

• The Hippocampus
• Brain scans reveal activity in the hippocampus
  and certain areas of the frontal lobe when a
  memory is created
• The Cerebellum
• Memories for skills and conditioned associations

35
Retrieval

• Getting information out
• Aided by cues
• Associations
• Contexts

36
Context Effects
Percentage of Words Recalled
Same Contexts for hearing recall
Different Contexts for hearing recall
37
Moods and Memories

• Mood-congruent memory
• the tendency to recall experiences that are
  consistent with ones current good or bad mood

38
Forgetting

• Encoding failures
• the info never gets in
• Storage failures
• fading of the memory record
• Retrieval failures
• from lack of retrieval cues or from the
  interfering effects of other learning

39
The End