Transcript EWT - Enjoy Psych

Reliability of one
cognitive process
Eyewitness Testimony
Elizabeth Loftus
AIM
This aim of this study was to investigate
the effect of leading questions on
eyewitness accounts and also the effect
that leading questions might have on later
memory for what happened.
 Is eye witness testimony reliable?
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Method
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2 Lab experiments
Design: Both between subjects
 5 groups in experiment 1,
 3 groups in experiment 2
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Experiment 1 Hypothesis
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There will be differences in speed
estimates of a car crash dependant on the
verb used in the critical question

What would the null hypothesis be?
Experiment 1: How the data was
collected
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Sample: 45 University students. Mainly young
and white. Both sexes.

Situation: Several short clips of traffic accidents
from a safety film were shown on a television
Task: Participants were put into 5 different
groups depending on which verb they
would get in the critical question. They
then watched the clips.
 After each clip the participants were given
a questionnaire asking them to describe
what they had seen and then answer the
critical question “estimate how fast the
cars were going when [hit, smashed,
bumped, collided, contacted] each other”


Experimenter recordings: Recorded the
estimate of speed in MPH
Critical Question
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The five conditions
(verbs) were
CONTACTED
HIT
BUMPED
COLLIDED
SMASHED
What do you think their findings
were?
Experiment 1: Findings

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The experiment found that there was a
difference between the speed estimates of
the 5 groups.
The ‘smashed verb’ created the highest
speed estimate in mph which was
approximately 40mph
The ‘contacted verb’ created the lowest
speed estimate which was approximately
30mph
Experiment 1: Conclusion
The findings suggest that eye witnesses
recall of events can be influenced by
wording of a question.
 The influence can be due to response bias
at the time of the question or actual
altering of memory permanently. A second
experiment is required to answer this
question

Look carefully at the scene I’m
going to show you.
Did you see any broken glass
on the ground at crash scene?
Experiment 2
Hypothesis

Participants will more likely falsely recall
broken glass one week after watching
footage of a car crash if the verb used in
the question is stronger.
Experiment 2: How the data was
collected

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Participants 150 university students mainly young
and white of both genders. Split into 3 groups;
group one gets hit verb, group 2 gets smashed
verb, group 3 gets no question (control group)
situation: shown 1 minute clip of car accident on
television
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Task: After the footage the 2 verb groups of
participants were asked to describe what they had
seen and answer the critical question used in
experiment 1. The control group was asked
nothing. A week later the participants came back
and answered the question ‘did you see any broken
glass?’
Experimenter recordings: Recorded speed
estimates and whether the participant said yes or
no to the question ‘did you see broken glass?’.
Experiment 2 Results

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There was a difference between recall of
broken glass between the 3 conditions
The ‘smashed verb’ caused the greatest recall
of broken glass (approximately 20%)
There was little difference between the control
group and the ‘hit verb’ recall (over 90%)
Experiment 2: Conclusion
The semantics of the question becomes
integrated with the memory of the event,
thus changing the memory and causing a
false memory to be constructed.
 What happens after we have witnessed an
event can alter our memory of the event.
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3/31/2016
Evaluation of studies:
Limitations of the study

All Loftus & Palmer’s participants were
students. Their memories may have
been different to other groups of
people, because they have to learn lots
of things for their studies. This means
they may be a biased group.
Limitations of the study

Loftus & Palmer’s studies are not true
to life because they are conducted in a
lab setting. So for instance, watching
video clips of car accidents would lack
the emotional impact of seeing an
accident for real, and this could affect
accuracy of memory. We know that
emotion affects memory. This means
the findings can’t confidently be
generalised to real life.
Limitations of the study

Loftus & Palmer’s findings can’t
confidently be generalised to the whole
population, partly because their study
lacked ecological validity so it isn’t true
to life, and partly because they used a
biased sample.
Limitations of the study

Loftus & Palmer’s findings can’t
confidently be generalised to the whole
population, partly because their study
lacked ecological validity so it isn’t true
to life, and partly because they used a
biased sample.
Strengths of the study

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In a lab experiment, extraneous variables
are controlled. This means the procedure
is replicable, and it means that cause and
effect can be linked.
The video clips and the length of time they were seen
were controlled so that all participants had the same
extraneous variables – only the wording of the critical
question varied between participants.
Strengths of the study

The method used is true to life, so the
findings can be generalised beyond the
research setting to everyday life.

(It is possible that the participants could
witness a car crash.)
Strengths of the study

The findings can confidently be
generalised to more people than just the
participants.
The findings and
conclusion can be used
to somehow improve the
quality of life in the future.
Application to
everyday life
Can be used to
explain behaviour that
wasn’t previously
understood
Loftus & Palmer’s
findings can be used
to help police develop
improved interview
techniques that avoid
using leading
questions, therefore
increasing the
accuracy of
witnesses’
testimonies.
Loftus & Palmer’s findings
have helped us understand
why it is that eye witnesses
often make mistakes when
giving evidence.
Improving Loftus & Palmer’s method
As you will have seen, Loftus & Palmer’s experiments can be criticised in a variety of ways.
1.
Your job is to design an improved method for investigating the effect of leading questions on eyewitness
testimony. You need to write your suggested method on a piece of A3 paper. The points you must include are:
•The method (lab experiment, field experiment, or case study)
•The design (independent measures or repeated measures)
•The sampling method (opportunity, systematic, volunteer, or random)
•The IV
•The DV
•Possible extraneous variables, and how you will control them
•A bullet-pointed, step-by-step procedure
2.
Swap your A3 sheet with another group. Evaluate each other’s methods. Use as many evaluative points as you
like, but they must be applied to the method, not general.
3.
When it’s your turn, your group must describe the other group’s method to the whole class, and explain your
evaluation of it. You need to rate their suggested method on a scale of 1 to 5, where 1 = very poor method (lots of
errors or bias, possibly unethical) and 5 = excellent method (well controlled and ethical).