Loftus & Palmer's study of distortion on witness memory

General aim:

• To test whether phrasing of questions about a car accident could alter participant's memory of events. 

Experiment 1 Aim:

• To see whether different verbs to describe a collision would affect the estimates of car speed.

Experiment 2 Aim:

• To investigate whether the estimates of speed were the result of memory distortion.

Experiment 1 Participants:

• Forty five students took part.

Experiment 2 Participants:

• One hundred and fifty students took part. 

Experiment 1:

• It was au lab experiment using independent measures design.
• Participants were shown 7 films of car crashes used by the Seattle police department.
• After watching the films, participants were asked to write an account of the accident and then answer a series of questions, in which all of them were fillers except for 1. 
• The IV was the verb used in the critical question.
• The DV was the estimated speed of car. 

Experiment 2:

• This was also a lab experiment using independent measures design.
• All particiants were given a questionaire that asked them to decribe the crash, then to answer a series of questions.
• 50 participants received a question asking how fast the cars were going when they 'smashed'
• 50 participants received a question asking how fast they were going when they 'hit'
• and a control group of 50 received questions that didn't ask about the speed.

Experiment 1:

• Quantitative data 
• Estimates of speeds were not affected by the actual speed.

• Film Number

  Actual speed (mph)

  Estimated speed (mph)

  1

  20

  37.7

  2

  30

  36.2

  3

  40

  39.7

  4

  40

  36.1

  
  

  Verb used

  Estimated speed (mph)

  Smashed

  41

  Collided

  39

  Bumped

  38

  Hit

  34

  Contacted

  32

Experiment 2:

• Particiapants who heard 'smashed' estimated higher speeds.
• More than twice as many people incorrectly remembered seeing broken glass hearing 'smashed'

Experiment 1:

• Estimates of the speed varied depending on the verb used, this could be becuase of:
• Response Bias - When unclear, participants were given hints to whether it was higher or lower.
• Memory Distortion - The verb used actually altered memry of the crash.

Experiment 2:

• Wording of questions actually distorts memory.