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Classic Evidence: Loftus & Palmer (1974) - Coggle Diagram
Classic Evidence: Loftus & Palmer (1974)
Methodology
Consists of two experiment conducted in a laboratory using an independent groups design
Each experiment conducted with a different set of pps:
Exp 1: 45 student pps
Exp 2: 150 student pps
Procedures
Experiment 1
45 pps asked to watch 7 film clips depicting a traffic accident. The clips ranged from 5-30 seconds (4/7 filns were staged)
They were then asked to fill in a questionnaire
Pps were separated into 5 groups and each group was then asked about how fast the vehicles were going when they 'hit/smashed/bumped/contacted/collided' with each other
The films were presented in a different order to each group
The experiment lasted 1hr 30min
One collision took place at 20mph, one at 30mph & the other 2 at 40mph
Experiment 2
Part 1
pps (150) asked to watch a traffic accident & then asked to fill in a questionnaire
the film depicted multiple car accidents less than 4 seconds
the pps were split into three groups: Group 1 - how fast when hit, Group 2 - how fast when smashed, Group 3 - no questions about speed (each group had 50pps)
Part 2
One week later all the pps were asked 'did you see any broken glass
There was no broken glass in the film but it was presumed those who said the car was going fast saw some broken glass
The question was embedded in a list of 10 & in a random position
Findings
Experiment 1
9 pps per verb:
Smashed - 40.8mph mean speed estimate
Collided - 39.3mph
Bumped - 38.1mph
Hit - 34.0mph
Contacted - 31.8mph
Two interpretations of these findings:
1 - Differential speed estimated results from response bias factors
2 - The form of the question causes a change in the subjects memory representation of the accident
Experiment 2
Part 1
Smashed mean estimate = 10.46mph
Hit mean estimate = 8mph
Pps gave higher speed estimates in the 'smashed condition just like in experiment 1
Part 2 (Broken Glass)
Smashed:
16 yes
34 no
Hit:
7 yes
43 no
Control:
6 yes
44 no
Conclusions
The form of a question can markedly & systematically affect a witness's answer to a question. Loftus & Palmer propose 2 explanation for this result
1 - Response Bias Factors: the different speed estimates occur because the critical word influences or biases a persons response
2- The memory representation is altered: the critical word changes a person's memory perception of the accident. Some critical words would lead to someone to have a perception of the accident having been more serious
If 2 is true than it is expected pps would 'remember' other details that are not true
This was tested in exp 2: in the 'smashed' condition, the 2 pieces of info combine to form memory of an accident that appears quite severe & therefore generates certain expectations (such as broken glass)
The findings from exp 2 suggest leading questions alter the memory a person has before the event
The findings can be understood in relation to research on the effects of verbal labels on to be remembered forms
Carmichael et al (1932) - verbal labels cause a shift in the way information is represented in memory in the direction of being more similar to the suggestion given by the verbal label
pps shown a s et of drawings & then provided with a verbal description
pps later asked to redraw images & the original object was affected by the verbal label
Evaluation
Methodology & Procedures
Controlled Experiment:
Loftus & Palmer conducted their research using experiments
an advantage of experimental design is that it demonstrates a causal relationship by deliberately manipulating the IV so the effect on the DV can be seen and a causal conclusion can be drawn
This is true in a lab study where potentially confounding variable are carefully controlled so any change in the DV is due to the IV & no other factor
Ecological Validity:
The pps watched the film clips of an accident which is not the same as watching a real accident
People don't take the task seriously/they are not emotionally affected in the way a real accident would affect them
Foster et al (1994): if pps thought they were watching a real robbery & their responses would influence a trial, the robber identification was more successful
Buckout et al (1980): a short film was shown on prime TV. Later a identity parade was shown & viewers were invited to phone in their choice of suspects - 14% were correct
The Sample:
pps were US college students
other groups may be more/less prone to being affected by misleading information
Age Differences:
consequences of source monitoring
an eye-witness typically acquires in for from 2 sources: observing & subsequent questions
studies found compared to younger subjects, elderly have difficulty remembering the source of their information even though their memory for the info itself is impaired -> become prone to misleading info
Alternative Evidence
Loftus conducted a study involving a cardboard cut-out of Bugs Bunny (Braun et al, 2002):
college students were asked to evaluate advertising material about Disneyland
In this material was misleading info about Bugs Bunny or Ariel (neither seen at Disneyland due to bugs not being Disney & Ariel not being introduced at that time)
pps assigned to the Bugs, Ariel/ Control Group
All visited Disneyland, pps in Bugs/Ariel more likely to report having shaken hands with them -> this shows how misleading info can create false memory
Ethical Issues & Social Implications
Lack of Valid Consent
Valid consent was not given from the pps as they were unaware of the aims of the study
However this would have affected the responses as they would have known the questions were leading and therefore behaviour would not reflect EWT in everyday life & not provide useful insights
Issue: whether deceptioin is acceptable? Can the researchers justify it in terms of importance & it had profound effects on understanding of EWT. PPS view of deception maybe mild. They were not psychologically harmed
Psychological Harm
Criticism of the study is that a real accident was not witnessed therefore PPS may not have responded the way an EW would in a real accident
An alternative may have been to expose PPS to a real accident but this may have been disstressing leading to psychological harm
The study avoided ethical issue of psychological harm by using film clips