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)

Experiment 2

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

Part 1

Part 2

  • 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)
  • 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

Psychological Harm

  • 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
  • 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