Transcript Eyewitness Testimony

Eyewitness Testimony
Elizabeth Loftus
Aims/Objectives:
Aim: To start looking at memory in everyday life:
Objectives:
• To be able to understand the basis of EWT (Eyewitness
Testimony).
• To begin to understand the various stages of EWT
• To begin looking at factors that effect EWT
Task:
•Fill in the handouts. You have 5
minutes to do this.
Answers to tasks:
VISUO-SPATIAL
SKETCHPAD
HOLDS VISUAL MEMORIES
EG: FACES
EPISODIC BUFFER
ADDED IN 2000 (BADDELEY)
INTEGRATES INFORMATION from
the central executive, the visuospatial sketchpad and phonological
loop
LIMITED CAPACITY
CENTRAL
EXECUTIVE
MODALITY -FREE.
ROUGHLY THE SAME AS
ATTENTION
ALLOCATES RESOURCES TO
OTHER COMPONENTS
Application of memory
Memory research has valuable application
• Can you think of some examples?
• One relevance to real / day to day life is
eyewitness testimony (EWT)
How good is memory?
• You may be surprised how difficult it is to remember
what a 10p looks like without having one in front of
you
• There will be a number of inaccuracies
• We do not need to have 100% recall for all
information we use everyday. For example we only
need to know the shape of coins and notes to be able
to use them correctly.
TASK: pg 48 in your packs…
In pairs and without looking anything up, try to do the
following 2 tasks.
1. Draw a picture of a 10p coin, front and back.
2. Write down the person on the front of a £5 note. Write
down the words written at the top of the front of the
note of any denomination (i.e. £5, £10, £20, £50).
• Watch the clip carefully
• Half way through I will stop the video and you
must write down all the changes you saw in the
clip. Over all there are 21. You have 3 minutes!
• Test Your Awareness : Whodunnit? - YouTube
Schemas
• Knowledge packages built up through our experience of
the world. They also help us to interpret new experiences.
• For example-knowing that there will be tables and chairs
in a restaurant. This would be your restaurant schema.
• They help to fill in gaps in knowledge we have.
• However they can lead to distortions when new
information doesn’t fit properly into our existing
knowledge.
• Cultural experiences and stereotypes affect memory.
• These distortions are particularly interesting when we
look at EWT.
Research findings on the role of
schemas:
•
Brewer and Treyens (1981) looked at the
effects of schemas on visual memory.
•
•
They asked 30 p’s, one at a time, to wait in a
room that had been set up to look like an
office for 35 seconds.
In the room there were objects such as a desk,
chair, calendar and typewriter
•
These objects were compatible with an
office schema
•
However there were a few items that
were non-compatible, such as a skull, a
pair of pliers and a brick.
Continued:
In an unexpected recall task the following results were found:
• P’s recalled the obvious office items that fitted with schema
expectancy, but were less successful at recalling the strange
items
• 8 p’s, however, recalled the really bizarre item-the skull
• Most errors in recall were substitutions.
• For example p’s would add in items that weren’t there such as pens,
books, and a telephone, which would have a high schema expectancy but
weren’t there on this occasion.
TASK…
1.
Why do you think that some p’s recalled seeing a skull in the
office (Brewer and Treyens, 1981)?
You have 3 minutes to answer the question. Prepare to feedback.
EWT Stages:
1. The witness encodes info into LTM (the event
and the person involved)
may be partial as the event occurs quickly, at night and
accompanied by rapid, violent, complex action
2. Witness retains info for a time.
Memories may be lost or modified during retention, other
activities may interfere with the memory itself
3. Witness retrieves memory from storage.
What happens next is there may be a presence or absence of
info that may affect the accuracy of the memory.
Factors affecting EWT:
• Turning to the person next to you, identify at least 5 factors that
you think could affect an eyewitness’s account
• Consider why and how these factors could affect
• You have 5mins – be prepared to feed back to the class 
The main factors affecting accuracy of memory can be placed into two
categories:
1. Witness factors: age, race, gender and individual response to
anxiety or stress.
2. Event factors: duration of event and level of violence witnessed.
We will be looking at age, anxiety and the effect of misleading
information.
Misleading Information
1 - Leading Questions
2 - Post Event Information
Loftus
Factors affecting eyewitness testimony:
• Elizabeth Loftus is a psychologist who argues that
eyewitness testimony in court is very unreliable.
• She looked at:
• whether people reconstruct memory,
• whether the memory persists (stays) or
• whether they can be ‘led’ in to answering in a certain way.
Loftus and Leading Questions
How does information
presented after an event
affect a witness’s memory
for that event?
Procedure
Experiment 1
45 participants took part.
• They all saw a video of a traffic accident.
• After the video they were all asked the same questions about the
accident.
• Apart from 1 question which was about the speed the cars were going
‘About how fast were the cars going when they ________ each
other’
Each group was given a different verb to fill in the blank. These
verbs were ‘smashed, collided, bumped, hit or contacted’.
Therefore the independent variable was the verb used.
The dependent variable was the estimate of speed given by the
participants
Results
Experiment 1
Verb
Smashed
Collided
Bumped
Hit
Contacted
Mean Speed
Estimates
40.8
39.3
38.1
34.0
31.8
What do these results show?
• How the question was
phrased influenced the
participants’ speed
estimates
• When the verb
‘smashed’ was used,
participants estimated
that the cars were
travelling much faster
than when the verb
‘contacted’ was used.
Conclusion
We can conclude that people’s memory for an event can be
influenced by the questions they are asked about it and those
questions can distort (change) our long term memory for an event
We don’t know whether the reported speed was due to a genuine
change in the participant’s memory, or through demand
characteristics (participants guessing the true nature of the
experiment)
Procedure
Experiment 2
150 student participants were shown a short film that showed a multivehicle car accident and then they were asked questions about it.
The participants were split into 3 groups (with 50 in each group)
1. One group was asked:
‘How fast were the cars going when they hit each other?’
2. The second was asked:
‘How fast were the cars going when they smashed into each other?’
3. The third group was not asked about the speed of the vehicles
One week later, all participants returned and were asked:
‘Did you see any broken glass?’
There was no broken glass in the film.
Results
Experiment 2
Did you see any broken glass?
Response
Yes
No
Smashed
16
34
Hit
7
43
Control
6
44
What do these results show?
The results show that the verb used in the original question influenced
whether the participants thought they had seen broken glass.
Conclusion
There seems to be evidence that suggests post event misleading
questions can have an adverse effect on EWT.
Task: using your text books and this PP complete pgs50-54 in your packs.
Research methods check:
• Do you think that demand characteristics may have affected the
results of Loftus and Palmers study? Explain your answer.
• What extraneous variables could have effected the results of the
study?
• What method was used? And how might that have effected the
results?
Work in pairs to answer the questions. You have 5 minutes.
Now, complete a GRAVE!
Questions to consider:
• How useful was the research?
(How can the results of the study be Applied to other situations?)
• How realistic were the studies?
(Think about the differences between the tasks the participants did, and real life situations
where you need to remember what you have seen)
• Who were the participants?
(Could the results be Generalised to other people?)
• Any other issues
(Think about the type of tasks, the content of the video, etc)
• What differences would there be in ‘real life situations?’
• How easy is it to estimate speed?
• What if the car had been a Porsche or a Smart Car?
• Was the memory really changed?
2 - Post event Discussion / Information
If you witness a crime and then discuss it with another person,
what could happen?
CONTAMINATION!!!
GABBERT (2003)
P - Pairs of p’s watched a video of the same crime but
filmed from different viewpoints
• Each P therefore had different elements of the event
• Both p’s then discussed with their partner before
individually answering questions
R - 71% p’s mistakenly recalled aspects of the event that
they did not see
• They had picked this info up through discussion
• Control group – no discussion – 0%
C - Witnesses go along with each other
Why??!! Is there any other explanation we have looked
at that could explain this?
SOCIAL
APPROVAL?
THEY BELIEVE
THE OTHER
PERSON IS
CORRECT – ISI???
MEMORY
CONFORMITY!!
Complete pg 55 in your pack
Ticket to leave….
• One thing I have learned….
• One question I still have….
Question 1
What are the two types of
cue in the cue-dependent
theory of forgetting?
Question 2
Name two psychologists
who have studied memory
and say which theory/topic
it relates to.
Question 3
Give one fact about the
participants in Loftus and
Palmer’s study.
Question 4
Explain in your own words,
what a memory trace is.
Question 6
Give two features about the
short-term memory store.
Question 7
Name three of the verbs
used in Loftus and Palmer’s
study.