Lindsay,
D.S., Allen, B.P., Chan, C.K. & Dahl, L.C. (2004). Eyewitness suggestibility and source similarity:
Intrusions of detail from one event into reports of another event. Journal of Memory and Language, 50,
96-111.
The overall purpose of this study was to determine the
effects on misinformation from changes in the similarity of narratives
presented along with a witnessed event.
The authors also included discussion of results and their prediction
compared to the source-monitoring framework previously described in similar
studies.
Experiments 1A and 1B
These
two experiments were identical except that 1A was conducted on the internet and
1B was conducted in the lab. The goals
of these experiments were as follows:
Methods
The witnessed event for both experiments was presented in
a slide and text format, with color slides showing a picture of the event and a
text description of the action occurring on the slide. The slides showed a man searching for a gold
coin in a house. As the man searches for
the missing item he encounters other items in proximity. These items provided the details for the
intrusion of information. The same-event
narrative described the man’s search but included some false items. The dissimilar-event narrative described a
parallel event of a girl cleaning the house.
The same false items were included, but these items were encountered in
a different order. Additionally, half of
the participant were warned that the information given
in the narratives may not have been included in the slide and that they should
answer based only on the slides.
Results and Discussion
Results for both of these experiments were nearly
identical, suggesting that web-based research may be reasonable. These experiments did replicate Allen and
Lindsay (1998), i.e. there was significant suggestibility present in the memory
of the participants. This intrusion of
detail did occur reliably in the dissimilar-event condition, although it
occurred significantly more frequently in the same-event narrative
condition. Interestingly there was not a
significant difference between the warning conditions, suggesting that the
participants were not knowingly answering the questions based on the same-event
narrative.
Experiment 2
The
second experiment was conducted to follow two aims that came out of experiments
1A and 1B. The first goals was to
replicate the result of 1A and 1B using new materials, including a video
instead of slides. Additionally, the
experiment tested for differences in intrusion rates when the narrative
followed a similar them versus a dissimilar theme.
Methods
This experiment used an 8-minute segment of the Blake
Edwards classic Return of the Pink
Panther as the witnessed event. The sound was replaced by and new audio
track created by the experimenters describing the events taking place. There were three postevent
narratives. The same-event narrative
described the actual event. The
similar-event narrative described a burglary that happened in a palace (the
original took place in a museum). The dissimilar-event
narrative described a school trip to a palace.
Each of these narrative included sets of suggestions that might
potentially make there way into memory.
Results and Discussion
The same-event and similar-event conditions replicated
the findings of 1A and 1B.
Interestingly, there was no difference in the number of intrusion from
the similar-event and dissimilar-event conditions. This would go against the SM prediction that
similarity would increase intrusions.
The experimenters propose that this finding may be due to the
possibility that participants see the source as related on a generic level and
based on temporal proximity. Thus…
Experiment 3
The experimenters wished to test for effects of disguising
the relationship between witnessed event and similar- or dissimilar-event
narratives.
Methods
To accomplish this disguise, the narratives and video
were presented in separates session described as separate experiment 24 hours
apart. In the first session participants
listened to the narrative and in the second session the video was watched. The
video was the same as the previous experiment.
The similar-event narrative described a burglary in a palace and the
dissimilar-event narrative described a school trip to a palace, as in
experiment 2.
Results and Discussion
The intrusion rates for the similar-event condition were
significantly higher than the rate for the dissimilar-event condition.
Experiment 4
The
purpose of this fourth experiment was to compare the results of experiments 2
and 3, using the same materials and method to avoid a cross experiment
comparison.
Methods
The materials from experiment 3 were used in this
experiment. Participants were assigned to either a 1 day condition (simulating
experiment 2) or a 2 day condition (simulating experiment 3).
Results and Discussion
Not surprisingly, the 1 day condition replicated the
results of experiment 2 and the 2 day condition replicated the results of
experiment 3. It appears that the close
proximity of presentation in the 1 day condition counteracts the effects of
thematic similarity. Additionally, there
was more false recall in the 2 day condition than the 1 day condition. This is explained as due to the recency and memory strength related to the information in
the 1 day condition. The Ps have just received this information and can better discern
its source.
General Discussion
The main conclusion are that details from a narrative can
intrude into the memories for details of another even, although this happens
less frequently when the narrative does not describe the exact witnessed event.
In addition, the intrusions are more likely from similarly themed narratives
than different narrative, when the two are sufficiently disguised. This issue is important, as witnesses in the
real world may hear other narratives of the crime or may have experienced
similar happening in the past.