D
2.8
Loftus and Palmer (1974)
Study in detail: To investigate the effect of leading questions on eyewitness recall ability
Aims
The aims of Loftus and Palmer (1974) were to see what the effect of leading questions were on eyewitnesses’ ability to
recall information. The study consisted of two separate experiments. The first, and more famous one, showed various
participants video clips of car crashes and they were asked to estimate the speed the cars were travelling at upon collision
dependent upon the phrasing of the question asked by experimenters.
Experiment 1: Procedure
45 student participants were put into groups and shown short films involving car accidents. After each film they were
shown, they were given a questionnaire to fill in, where only one question was critical: estimation of the speed that the
cars were travelling at. There were five different conditions for this experiment, which differed only by the phrasing of the
critical question. In one group, participants were asked “how fast do you think the cars were travelling when they hit each
other”, and another was asked “how fast do you think the cars were travelling when they smashed into each other”. The
only word that differed between the groups was the choice of verb. Apart from ‘hit’ and ‘smashed’, the words ‘collided’,
‘bumped’ and ‘contacted’ were used also.
Altogether, there were seven films shown to the participants. In order to get a precise series of results, the average
estimation was taken for each participant group. Four of the films were staged crashes, so the researchers knew the
actual speeds of those cars (one film used cars travelling at 20mph, another at 40mph and two at 30mph), but the other
three films showed real car crashes where the speed was not certain.
Experiment 1: Findings
Loftus and Palmer (1974) found significant jumps between average estimations depending upon the severity of the verb:
 ‘smashed’ gave an average estimate of 40.8mph
 ‘collided’ gave an average estimate of 39.3mph
 ‘bumped’ gave an average estimate of 38.1mph
 ‘hit’ gave an average estimate of 34.0mph
 ‘contacted’ gave an average estimate of 31.8mph
Evidently, the more “extreme” the verb was in the question, the higher the average estimation of the cars’ travelling
speeds. This allowed Loftus and Palmer to conclude whether or not leading questions had an effect on eyewitnesses.
Experiment 1: Conclusions
Loftus and Palmer concluded that the phrasing of the questions had a clear effect on witnesses’ answers, and therefore
that leading questions can affect the way that eyewitnesses respond in a real situation. However, Loftus and Palmer were
not sure if the choice of verb in the leading question was the factor affecting recall, or if perhaps the participants
purposely used the phrasing of the question to help them estimate an accurate speed (as the researchers agreed it might
be difficult to accurately distinguish speeds between 20 and 40mph).
Experiment 2: Procedure
In this second experiment, a sample of 150 student participants were shown a clip of a car collision. This clip was four
seconds long, and different to any of those used in the first experiment. There was no broken glass as a result of the crash
in the clip. The participants were then asked questions about the brief video they had seen.
The participants were divided into three condition groups. The same critical question as before, “how fast do you think
the cars were travelling when they (insert verb) each other?” was asked to two of the three groups, where group one was
given the verb ‘smashed’ and group two given ‘hit’. The third group however, was not asked about speed.
One week later, the participants were given a second questionnaire to fill in. This included the same critical question
about speed that they were given before (i.e. group one were asked the ‘smashed’ question, group two the ‘hit’ question)
and group three not asked the critical question. All groups, though, were asked “did you see any broken glass?”
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Experiment 2: Findings
The answers to the question “did you see
any broken glass?” from the second
questionnaire are shown to the right.
response:
yes
no
‘smashed’
16
34
‘hit’
7
43
control
6
44
total
29
121
The averages were statistically different at p<0.05. A Chi-squared test was carried out and the result was 7.76, which is
significant to p<0.025.
Experiment 2: Conclusions
It was concluded that memory is fed by the event and by external information also provided afterwards. Over time, both
sources are integrated into one memory. The findings of this second experiment support those of other similar
experiments, including Loftus and Palmer’s (1974) first laboratory experiment, which have also shown that external forces
can affect witness recall.
Evaluation
Strengths
 Both parts of Loftus and Palmer (1974) are laboratory experiments with strong, scientific controls (for example, they
all watched the same film and were asked identical questions – except for the verb change), which means the study is
replicable and can be repeated to test for reliability
 The use of estimates of speed in both experiments and the ‘yes’/’no’ question of the second experiment yielded
quantitative data which meant there was no subjective interpretation of the data – therefore it can be said that the
experiments have objectivity
Weaknesses
 The validity of the task is questionable, as the student participants are not likely to have been under the same
emotional strain a real eyewitness of a horrific accident would have been, likewise they only watched video clips of
the car crashes and did not witness them first-person, which may have affected their responses
 Students were used only, so the findings of the experiments may not be necessarily generalisable to the population as
a whole until repeated on other groups
 The student participants may have figured out what the purpose of the study was and tried to amend their answers to
help out the researchers accordingly, there may have been demand characteristics
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