Week 1
Chapter 6
6.1 INTRODUCTION
The chapter opens by referencing the recent Paris terror attacks,
where 130 people lost their lives, and 350 were injured. Witness
accounts are crucial in understanding the unfolding of these events.
Witness Accounts Variability:
o Different survivors reported varying details: some said the
attackers were silent, while others heard them shout "It's for
Syria."
o Discrepancies in descriptions of the attackers: some said one
of the attackers was female, others only saw male attackers.
o Some victims could not recall specifics about the attackers due
to their focus on the trauma around them.
The chapter examines key factors affecting witness memory, such
as:
o Attention during the event
o Stress and weapon exposure influencing memory storage
o The delay between events and police testimonies
o The impact of media reports on memory accuracy
Witness Testimony:
o Plays a crucial role in criminal investigations and court
decisions. The accuracy of witness memory has been
extensively studied, with historical reference to Hugo
Münsterberg’s 1908 book On the Witness Stand, which laid the
foundation for experimental psychology in evaluating
testimony.
o Inaccurate testimony is a leading cause of wrongful
convictions, underscoring the importance of studying memory
accuracy in criminal investigations.
6.2 THE MEMORY PROCESS
Stages of Memory:
o Encoding: The process of creating a memory, which can be
impaired if the observer is distracted.
o Storage: Retaining the memory for later recall. External
influences, such as hearing others' incorrect descriptions, can
contaminate stored memories.
o Retrieval: Accessing the memory. The context, such as stress
or an unfamiliar setting (e.g., a police station), can affect the
accuracy of retrieval.
Example of Encoding Impact:
o If someone witnesses a crime while distracted (e.g., focused
on an essay), they may not clearly encode the event, affecting
later recall.
Memory Accuracy in Real-Life vs. Lab Settings:
, o Real-life crime memories may be more accurate than those
from lab simulations. A study by Yuille and Cutshall (1986) on
witnesses to a fatal shooting found that their memories were
largely accurate even months after the event.
6.3 ESTIMATOR VS. SYSTEM VARIABLES
Eyewitness Testimony:
o Vital in criminal cases, influencing judicial decisions. It's
important to understand the factors that affect its accuracy.
Types of Variables:
o Estimator Variables: Factors beyond the control of the legal
system that affect encoding and storage. Examples include
stress, distance from the event, lighting conditions, and
memory contamination by external sources.
o System Variables: These relate to retrieval and can be
controlled by the justice system, such as the type of questions
asked during police interviews. Careful handling of system
variables can prevent further memory distortion.
6.4 ENCODING FACTORS
Factors Affecting Encoding: Various factors can influence how
accurately a witness encodes a memory. These include:
o Stress: High stress can impair encoding quality, but the
relationship is complex.
o Weapon Presence: Witnesses may focus more on the
weapon and less on other details of the event.
o Change Blindness: A phenomenon where witnesses fail to
notice changes in their environment.
o Stereotyping: Prejudices or stereotypes may distort how
events are encoded.
o Intoxication: Alcohol or drugs can impair the encoding
process.
o Witness Characteristics: Stable traits like age can also
influence memory accuracy.
6.4.1 Stress
Stress and Memory:
o High stress levels during a crime can impact memory
accuracy, often making it more difficult to recall peripheral
details but enhancing the recall of central aspects.
o Yerkes-Dodson Law (1908): Suggests an inverted U-shape
curve, where memory performance is optimal under moderate
stress but declines under extreme stress.
Studies on Stress:
o Research by Valentine and Mesout (2009) showed that higher
stress (measured by heart rate) led to fewer correct
descriptors and more incorrect ones when describing events.
, o Morgan et al. (2013) found that military personnel in stressful
environments (e.g., mock prisoner of war camps) were more
susceptible to misinformation.
Contradictory Findings:
o In a real-life study (Yuille & Cutshall, 1986), witnesses under
higher stress remembered the event more accurately than
those less stressed.
o Stress may narrow attention to central details of an event,
enhancing recall of those aspects, while peripheral details may
be forgotten.
Traumatic Memories:
o Extremely stressful, traumatic memories are often very
accurate due to their emotional significance. However, trauma
can also cause narrowing of focus, leading to gaps in memory
for non-central details.
Study by Hope et al. (2015):
o In a scenario involving an armed assailant, police officers with
higher stress (due to being armed) remembered central
features of the event less accurately than those with lower
stress (the observers).
6.4.2 Weapon Focus
In crimes involving violence, weapons like guns or knives often play
a central role.
Research suggests that witnesses may focus on the weapon due to
fear or surprise, often forgetting other details.
Laboratory studies show a "weapon focus" effect, but real-life
evidence is less clear (Cutshall & Yuille, 1989; Behrman & Davey,
2001).
A review found that weapon focus is an important factor in
eyewitness memory accuracy (Fawcett et al., 2013).
Longer exposure to the perpetrator reduces weapon focus, shifting
attention to the perpetrator instead.
Two main explanations:
o Threat hypothesis: People focus on the weapon due to the
threat it poses (Easterbrook, 1959).
o Unusualness hypothesis: Weapons capture attention
because they are unusual in everyday life.
Being aware of weapon focus can help people recall more details of
a crime (Pickel, Ross, & Truelove, 2006).
6.4.3 Change Blindness
Change blindness occurs when witnesses fail to notice changes while
shifting their attention.
In a study, 61% of participants didn’t notice the identity of a burglar
changing during a crime video (Davies & Hine, 2007).
Change blindness happens because of a lack of a clear mental
representation, leading to memory errors.
More research is needed to explore how change blindness affects
eyewitness testimony in real-life crimes (Laney & Loftus, 2010).
6.4.4 Stereotyping
, Crime events can be complicated, leading people to rely on schemas
or stereotypes to fill in memory gaps.
Stereotypes can affect memory by making people more likely to
remember details that fit their expectations.
A study showed that participants remembered more incriminating
details when a suspect was described as a drug addict, especially
under high cognitive load (Van Knippenberg et al., 1999).
Older adults may rely more on stereotypes and schemas, potentially
leading to memory errors (García-Bajos et al., 2012).
Information consistent with stereotypes might be remembered
better, but repressing stereotypical thinking can lead to more errors
(Peters et al., 2006).
6.4.5 Intoxication
Intoxicated witnesses or victims may have impaired memory due to
narrowed attention, focusing more on central details.
Studies suggest that intoxicated individuals recall fewer peripheral
details but may be accurate about central details (Schreiber Compo
et al., 2011).
Not all studies support this, and some suggest that beliefs about
alcohol's effects may be more harmful than alcohol itself (Assefi &
Garry, 2003).
Intoxicated witnesses might provide less information but can still be
accurate about what they remember (Flowe et al., 2015).
6.4.6 Age
Age influences memory accuracy, with young adults having the most
reliable memories.
Older adults may struggle with encoding due to age-related
cognitive decline (Li et al., 2005).
Older witnesses often recall fewer details or less accurate
information compared to younger adults (Aizpurua et al., 2009).
Children’s memories are less reliable due to limited life experience,
but their memory improves as they age (Baker-Ward et al., 1993).
6.5 STORAGE FACTORS
This section explores how various factors affect how events are stored in
memory, particularly in the context of eyewitness testimony.
6.5.1 Post-event Information
Witness separation: Often done by police to prevent conformity
and misremembering.
Witness discussions: Witnesses might talk about the event,
leading to incorporating details they didn’t actually observe.
Misinformation effect: When memory is altered by misleading
information (Loftus & Hoffman, 1989).
Case studies:
o Oklahoma City Bombing (1995): Witnesses initially
misremembered McVeigh’s accomplice after discussing with
others.
o Jill Dando Murder (1999): A witness changed their mind after
talking to others, influencing others’ memories.
Chapter 6
6.1 INTRODUCTION
The chapter opens by referencing the recent Paris terror attacks,
where 130 people lost their lives, and 350 were injured. Witness
accounts are crucial in understanding the unfolding of these events.
Witness Accounts Variability:
o Different survivors reported varying details: some said the
attackers were silent, while others heard them shout "It's for
Syria."
o Discrepancies in descriptions of the attackers: some said one
of the attackers was female, others only saw male attackers.
o Some victims could not recall specifics about the attackers due
to their focus on the trauma around them.
The chapter examines key factors affecting witness memory, such
as:
o Attention during the event
o Stress and weapon exposure influencing memory storage
o The delay between events and police testimonies
o The impact of media reports on memory accuracy
Witness Testimony:
o Plays a crucial role in criminal investigations and court
decisions. The accuracy of witness memory has been
extensively studied, with historical reference to Hugo
Münsterberg’s 1908 book On the Witness Stand, which laid the
foundation for experimental psychology in evaluating
testimony.
o Inaccurate testimony is a leading cause of wrongful
convictions, underscoring the importance of studying memory
accuracy in criminal investigations.
6.2 THE MEMORY PROCESS
Stages of Memory:
o Encoding: The process of creating a memory, which can be
impaired if the observer is distracted.
o Storage: Retaining the memory for later recall. External
influences, such as hearing others' incorrect descriptions, can
contaminate stored memories.
o Retrieval: Accessing the memory. The context, such as stress
or an unfamiliar setting (e.g., a police station), can affect the
accuracy of retrieval.
Example of Encoding Impact:
o If someone witnesses a crime while distracted (e.g., focused
on an essay), they may not clearly encode the event, affecting
later recall.
Memory Accuracy in Real-Life vs. Lab Settings:
, o Real-life crime memories may be more accurate than those
from lab simulations. A study by Yuille and Cutshall (1986) on
witnesses to a fatal shooting found that their memories were
largely accurate even months after the event.
6.3 ESTIMATOR VS. SYSTEM VARIABLES
Eyewitness Testimony:
o Vital in criminal cases, influencing judicial decisions. It's
important to understand the factors that affect its accuracy.
Types of Variables:
o Estimator Variables: Factors beyond the control of the legal
system that affect encoding and storage. Examples include
stress, distance from the event, lighting conditions, and
memory contamination by external sources.
o System Variables: These relate to retrieval and can be
controlled by the justice system, such as the type of questions
asked during police interviews. Careful handling of system
variables can prevent further memory distortion.
6.4 ENCODING FACTORS
Factors Affecting Encoding: Various factors can influence how
accurately a witness encodes a memory. These include:
o Stress: High stress can impair encoding quality, but the
relationship is complex.
o Weapon Presence: Witnesses may focus more on the
weapon and less on other details of the event.
o Change Blindness: A phenomenon where witnesses fail to
notice changes in their environment.
o Stereotyping: Prejudices or stereotypes may distort how
events are encoded.
o Intoxication: Alcohol or drugs can impair the encoding
process.
o Witness Characteristics: Stable traits like age can also
influence memory accuracy.
6.4.1 Stress
Stress and Memory:
o High stress levels during a crime can impact memory
accuracy, often making it more difficult to recall peripheral
details but enhancing the recall of central aspects.
o Yerkes-Dodson Law (1908): Suggests an inverted U-shape
curve, where memory performance is optimal under moderate
stress but declines under extreme stress.
Studies on Stress:
o Research by Valentine and Mesout (2009) showed that higher
stress (measured by heart rate) led to fewer correct
descriptors and more incorrect ones when describing events.
, o Morgan et al. (2013) found that military personnel in stressful
environments (e.g., mock prisoner of war camps) were more
susceptible to misinformation.
Contradictory Findings:
o In a real-life study (Yuille & Cutshall, 1986), witnesses under
higher stress remembered the event more accurately than
those less stressed.
o Stress may narrow attention to central details of an event,
enhancing recall of those aspects, while peripheral details may
be forgotten.
Traumatic Memories:
o Extremely stressful, traumatic memories are often very
accurate due to their emotional significance. However, trauma
can also cause narrowing of focus, leading to gaps in memory
for non-central details.
Study by Hope et al. (2015):
o In a scenario involving an armed assailant, police officers with
higher stress (due to being armed) remembered central
features of the event less accurately than those with lower
stress (the observers).
6.4.2 Weapon Focus
In crimes involving violence, weapons like guns or knives often play
a central role.
Research suggests that witnesses may focus on the weapon due to
fear or surprise, often forgetting other details.
Laboratory studies show a "weapon focus" effect, but real-life
evidence is less clear (Cutshall & Yuille, 1989; Behrman & Davey,
2001).
A review found that weapon focus is an important factor in
eyewitness memory accuracy (Fawcett et al., 2013).
Longer exposure to the perpetrator reduces weapon focus, shifting
attention to the perpetrator instead.
Two main explanations:
o Threat hypothesis: People focus on the weapon due to the
threat it poses (Easterbrook, 1959).
o Unusualness hypothesis: Weapons capture attention
because they are unusual in everyday life.
Being aware of weapon focus can help people recall more details of
a crime (Pickel, Ross, & Truelove, 2006).
6.4.3 Change Blindness
Change blindness occurs when witnesses fail to notice changes while
shifting their attention.
In a study, 61% of participants didn’t notice the identity of a burglar
changing during a crime video (Davies & Hine, 2007).
Change blindness happens because of a lack of a clear mental
representation, leading to memory errors.
More research is needed to explore how change blindness affects
eyewitness testimony in real-life crimes (Laney & Loftus, 2010).
6.4.4 Stereotyping
, Crime events can be complicated, leading people to rely on schemas
or stereotypes to fill in memory gaps.
Stereotypes can affect memory by making people more likely to
remember details that fit their expectations.
A study showed that participants remembered more incriminating
details when a suspect was described as a drug addict, especially
under high cognitive load (Van Knippenberg et al., 1999).
Older adults may rely more on stereotypes and schemas, potentially
leading to memory errors (García-Bajos et al., 2012).
Information consistent with stereotypes might be remembered
better, but repressing stereotypical thinking can lead to more errors
(Peters et al., 2006).
6.4.5 Intoxication
Intoxicated witnesses or victims may have impaired memory due to
narrowed attention, focusing more on central details.
Studies suggest that intoxicated individuals recall fewer peripheral
details but may be accurate about central details (Schreiber Compo
et al., 2011).
Not all studies support this, and some suggest that beliefs about
alcohol's effects may be more harmful than alcohol itself (Assefi &
Garry, 2003).
Intoxicated witnesses might provide less information but can still be
accurate about what they remember (Flowe et al., 2015).
6.4.6 Age
Age influences memory accuracy, with young adults having the most
reliable memories.
Older adults may struggle with encoding due to age-related
cognitive decline (Li et al., 2005).
Older witnesses often recall fewer details or less accurate
information compared to younger adults (Aizpurua et al., 2009).
Children’s memories are less reliable due to limited life experience,
but their memory improves as they age (Baker-Ward et al., 1993).
6.5 STORAGE FACTORS
This section explores how various factors affect how events are stored in
memory, particularly in the context of eyewitness testimony.
6.5.1 Post-event Information
Witness separation: Often done by police to prevent conformity
and misremembering.
Witness discussions: Witnesses might talk about the event,
leading to incorporating details they didn’t actually observe.
Misinformation effect: When memory is altered by misleading
information (Loftus & Hoffman, 1989).
Case studies:
o Oklahoma City Bombing (1995): Witnesses initially
misremembered McVeigh’s accomplice after discussing with
others.
o Jill Dando Murder (1999): A witness changed their mind after
talking to others, influencing others’ memories.
