Forensic Psyc Eyewitness Memory

Question 1

Background

Answer 1

• Forensic investigations are an attempt
to reconstruct a past event
 Physical evidence (hair, fibers, fingerprints,
DNA)
 Eyewitness evidence (statements and
identification)
• Both forms of evidence are handled
very differently by the criminal justice
system

Question 2

Background

• Physical evidence

Answer 2

 Protocols for collecting,
preserving and interpreting
physical evidence are
dictated largely by forensic
scientists.
 Protocols have a scientific
foundation, grounded in
what experts suggest are
optimal ways to avoid
contamination.
 Physical evidence is often
‘circumstantial

Question 3

• Eyewitness Evidence

Answer 3

 Typically collected by non-specialists in human
memory.
 Protocols for collecting, preserving and interpreting
eyewitness evidence has not incorporated scientific
psychological research to the extent that it could.
 Often directly links suspect to crime.

Question 4

Why might the difference exist?

Answer 4

• Memory misconceptions: Loftus & Loftus
(1980), survey of 169 individuals: 84%
agreed with the statement;
• Metaphors of memory as like a videorecorder
- you just have to press ‘play’
and it all comes back to you…
“Everything we learn is permanently stored in
the mind, although sometimes particular details
are not accessible. With hypnosis, or other
special techniques, these inaccessible details
could eventually be recovered.”

• BUT psychologists know that memory is
fallible, malleable, reconstructive, susceptible
to suggestion, etc.
• So, it’s not surprising that eyewitness
testimony is amongst the least reliable forms
of evidence.

Question 5

How do we know eyewitness evidence is so

unreliable?

Answer 5

1. DNA exoneration case studies
   “Eyewitness misidentification is the single
   greatest cause of wrongful convictions [in the
   US], playing a role in nearly 75% of convictions
   overturned through DNA testing.” (www.innocenceproject.org)
    BUT these are examples rather than scientific
   evidence. They give a potentially misleading
   message.

2. Eyewitness research
Over 2000 publications to date
show that errors can occur at:
 Encoding (e.g., viewing
conditions)
 Storage (e.g., exposure to
post-event information)*
 Retrieval (e.g., interview
procedures; ID techniques)

Question 6

The Misinformation Effect

Answer 6

Exposure to incorrect information about
an event after it has occurred often
causes people to incorporate this
misinformation into their memories

Question 7

Three ways to encounter post-event

information:

Answer 7

1. Leading questions about the event
   (e.g., by police officer or
   therapist); Covered in Psyc1001
2. Hearing about the event from the
   media
3. Hearing about the event from
   other witnesses

Question 8

1. Leading Questions: Research

Answer 8

• 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

Question 9

2. Media Report: Research (Wright & Stroud, 1998)

Answer 9

• Showed Ps pictures of a shoplifting
incident.
• Ps then read a brief summary of the
crime, which included some incorrect
details.
• Results indicated that Ps incorporated
the incorrect details from the summary
into their memories

Question 10

Co-witnesses Talk

• Eyewitness Survey (Paterson & Kemp, 2006a)

Answer 10

– Majority of witnesses report discussing the event
with a co-witness
– Main reason for discussing the event with a cowitness:
Providing information
– More witnesses reported that they had been
encouraged by the police to discuss the event
with co-witnesses than discouraged

Question 11

The Legal Perspective

Answer 11

Hearsay: “a witness’s assertions of relevant facts
should be based upon his or her own experiences”
and not those of another (Forbes, 2003, p. 59).
• American, British, (and Australian?) guidelines
discourage discussion between witnesses

Question 12

Police Survey (Paterson & Kemp, 2005)

Answer 12

• 74% of police reported receiving instructions to
prevent discussion
• Police reported benefits of discussion
– Refresh and reinforce memory
– Recovery from trauma
– Witnesses with different stories impeded court
– Police officers discuss with one another
• Police reported impracticalities of preventing it
– Discussion prior to arrival
– Impossible to prevent
– Mother and child

Question 13

Comparing Ways to Encounter

Misinformation (Paterson & Kemp, 2006b)

Answer 13

Purpose
• To investigate the relative impact of different
methods of encountering postevent information.
Participants
• 105 undergraduate psychology students
(81 females, 24 males)

Procedure
1) Stimulus: Crime video
2) 1st Delay: 1 week
3) Postevent Information:
 Leading questions
 Media report
 Indirect co-witness information
 Co-witness discussion with confederate
 Control
4) 2nd Delay: 20 minutes
5) Individual Memory Task: Free recall, short
answer, and recognition questionnaire

Results
• No effect of Postevent Information Type on
memory accuracy for control items

For accurate information, direct and indirect co-witness conditions more accurate

For misleading information direct and indirect co-witness conditions less accurate

Question 14

Social Contagion of Memory

Answer 14

• Research has consistently shown that participants
often report misinformation that was previously
stated by a co-witness during discussion
• This phenomenon has become known as:
 “Social contagion of memory” (Roediger et al., 2001)
 “Memory conformity” (Wright, Self, & Justice, 2000)

Question 15

Warnings about Misinformation

Paterson, Kemp, & McIntyre, 2011

Answer 15

Purpose
• To determine whether the detrimental effects of
co-witness misinformation can be decreased by
warning participants about misinformation.
Participants
• 119 undergraduate psychology students
(97 females, 22 males)

Procedure
1) Stimuli: crime video (two versions)
2) 1st Delay: 20 minutes
3) Memory Elaboration:
 Different-video group (Misled)
 Same-video group (Non-misled)
 No Discussion
4) 2nd Delay: 1 week
5) Warning: (general, specific, or none)
6) Individual Memory Task: Free recall,
recognition questionnaire, and identification 

• For misled items, misled participants are less accurate than other conditions

For neutral items, misled participants are more accurate than other conditions

Misled participants reported more accurate propositions than non-misled participants

Warning had no effect on the recognition questionnaire or the free recall

Results
• Discussion Type and Warning had no effect
on eyewitness identification accuracy or
confidence

Question 16

Why does the misinformation effect occur?

Main theories explaining the misinformation effect:

Answer 16

1. Modification of the memory
   a) Alteration theories
   b) Coexistence theories
2. Social and demand factors (McCloskey & Zaragoza, 1985)
   The different theories for the misinformation effect
   have different practical implications

Question 17

Why does the misinformation effect
occur?
1a. Alteration hypothesis:

Answer 17

Original
information does not exist because:
i. Vacant slot explanation (Wright, 1995)
 Misinformation is accepted because
individual failed to encode original
information
ii. Overwriting explanation (e.g., Loftus, 1979)
 Postevent information overwrites the
original memory
iii. Blend explanation (e.g., Loftus, 1985)
 Ps encode misinformation in same cognitive
structure as the original information which
results in a blend (e.g., colours, numbers).

Question 18

Why does the misinformation effect
occur?
1b. Co-existence hypothesis:

Answer 18

Both
memory for original event and
misinformation are stored and each
memory is capable of being recovered.
Original memory is not replaced, but is
less accessible than the subsequent
misleading information, perhaps owing
to:
Recency effect (Murdock, 1962)
Retroactive interference (McGeoch, 1932)

Question 19

Why does the misinformation effect
occur?
2. Response bias

Answer 19

in favour of postevent information
Due to recognition test procedure
Ps who don’t remember/notice the
critical detail in the original event and
are not given any misinformation reply
at chance rate.
Ps who don’t remember/notice the
critical detail in the original event and
receive misinformation have no reason
to doubt misinformation presented to
them (e.g, McCloskey & Zaragoza, 1985).

Question 20

Factors influencing susceptibility to the

misinformation effect

Answer 20

People will be less susceptible to
misinformation if:
 They first make a public statement
about what they witnessed (Loftus, 1977)
 There is less time between witnessing
the event and the presentation of
misinformation (Loftus et al., 1978)
 The misinformation blatantly contradicts
what was originally witnessed (Loftus, 1979)
 Source of the misinformation in not
credible

 They are forewarned that they may
encounter misinformation (Greene, Flynn, & Loftus, 1982)
However, warning them that they have
encountered information a week after the
fact, doesn’t help combat the
misinformation effect (Paterson, Kemp, & McIntyre, 2011)

Factors that increase susceptibility to the
misinformation effect:
 Age (young and old)
 Hypnosis
 Suggestibility (Gudjonsson Suggestibility
Scale)
 Misinformation is repeated
 Misinformation is peripheral

Question 21

Limitations of research on the

misinformation effect

Answer 21

• Ethical constraints of laboratory research
• Ecological validity of lab findings
 Yuille & Cutshall (1986) investigated real
homicide with 20 witnesses (13
interviewed)
– Reports were accurate and detailed 5-6 months
after
– Witnesses were not susceptible to misinformation