reconstruction of automobile destruction elizabeth f. loftus and john c. palmer (1974)

Reconstruction of Automobile destruction

Elizabeth F. Loftus and John C. Palmer (1974)

Please read the title and look at the picture

Try to remember both

Curtains in a window

Bottle

Crescent moon

Beehive

Eye-glass

Seven

Ship’s wheel

Hour glass

Kidney bean

Pine tree

Gun

Two

Please read the title and look at the picture

Try to remember both

Diamond in a rectangle

Stirrup

Letter “C”

Hat

Dumbbells

Four

Sun

Table

Canoe

Trowel

Broom

Eight

Please draw as many of the pictures as you can

• Please write ‘1st group’ or ‘2nd group’ on your paper

Experiment

• Please hand your drawing to a member of the other group

• Check to see whether the drawing looks like one of a pair of objects

Curtains in a window or Diamond in a rectangle

Bottle or stirrup

Crescent moon or letter “C”

Beehive or hat

Eye-glass or Dumbbells

Seven or Four

Ship’s wheel or Sun

Hour glass or Table

Kidney bean or Canoe

Pine tree or Trowel

Gun or Broom

Two or Eight

Reconstruction of Automobile destruction

Elizabeth F. Loftus and John C. Palmer (1974)

Theory

• People are not good at reporting numerical details, such as time, speed and distance (Bird 1927).

• Marshall (1969) found that participants gave speed estimates ranging between 10 and 50 mph for a car travelling at 12mph!

Theory

• (Block 1974) Because people are poor at estimating they can be easily influenced by questioning, for example. In courts of law leading questions can not be asked.

• Fillmore (1971) found that the words `hit' and `smashed' could affect the estimated speed.

Experiment 1Method

• 45 students in groups of various sizes

• Would the results generalise?

• Are they just trying to please their teacher?

7 films from the local safety council and police

• 5 - 30 second film clips, of car accidents.

• Not really like a real accident, therefore lacks ecological validity

• After a written account of each accident was given by each student, a series of questions was asked.

• The critical question was one about the estimated speed of the vehicles.

Experiment 1 - Method

• What was the purpose of the written account?

• Did this affect the results?

• Loftus & Palmer fail to report any details of what was written

• What data could have been obtained from these accounts?

Experiment 1 - Method

• 5 groups of 9 students.

• Group sizes rather small

• Between 15 and 20 in each group is usually sufficient

• Each group had a different version of the critical question.

Experimental Conditions

• 1. About how fast were the cars going when they hit each other?

• 2. About how fast were the cars going when they smashed each other?

• 3. About how fast were the cars going when they collided with each other?

• 4. About how fast were the cars going when they bumped into each other?

• 5. About how fast were the cars going when they contacted with each other?

Independent Variable

• Different wording of the questions

Dependent Variable

• Speed estimates

Experiment 1 - method

• The time taken to conduct the experiment was about one hour and a half.

• Films were presented to the participants in different orderings

Experiment 1 - Results

Verb Mean speed estimate (mph)

Smashed 40.8

Collided 39.3

Bumped 38.1

Hit 34.0

Contacted 31.8

Experiment 1 - Results

• These differences are significant at p is less than 0.005.

• This means that less than five in every thousand times this experiment is run could the results possibly be owing to chance factors

• As chance results are unlikely we reject our null hypothesis

Experiment 1 - Hypothesis

• It is predicted that there will be a significant difference between speed estimates depending upon the verb used in the question about speed.

• This is known as a two-tailed experimental hypothesis because we are just predicting a difference without saying which verb has the greatest effect on speed estimation.

Experiment 1 - Did the actual speed of the cars affect the

estimateActual speed (mph) Mean estimates (mph)

20 37.7

30 36.2

40 39.7

40 36.1

Experiment 1 - Discussion

– 1. The participant is not sure of the speed so the verb provides the answer.

– 2. The verb changes the memory representation.

The results of experiment 1 suggest a research question for

experiment 2.

– If the memory representation is changed then we might expect the participant to ‘see’ other things that were not actually there.

Experiment 2 - Method

• 150 students were shown a film of a multiple car crash

• The film lasted one minute, but the action was just 4 seconds long.

• Three groups of 50 students were used.

• All students were asked to give a written description of the car accident

• A series of questions was asked

Experiment 2 - Critical questions

One group was asked: `About how fast were the cars going when they smashedsmashed into each other?'

The second group was asked `About how fast were the cars going when they hithit each other?'

The third group were not asked about the speed.

One week later

• The participants returned

• They did not see the film again

• They were again asked a series of ten questions about the film

• The critical question was “Did you see any broken glass?”

• The participants checked a box labelled ‘yes’ or a box labelled ‘no’.

Experiment 2 - Method

• The critical question appeared randomly in different positions

• There was no broken glass in the film

Experiment 2 - Results

Verb Mean Estimated speed mph

Smashed 10.46

Hit 8.00

Significant at p<0.05

Experiment 2 - Results

Verb condition

Response Smashed Hit Control

Yes 16 7 6

No 34 43 44

Significant at p<0.025

Probability of saying that there was broken glass

Speed estimate (mph)

Verb condition 1-5 6-10 11-15 16-20

Smashed .09 .27 .41 .62

Hit .06 .09 .25 .50

The verb ‘smashed’ affects speed estimate in a way that lies beyond saying that because ‘smashed’ suggests the cars were going fast when

they crashed there must have been glass.

Experiment 2 - Discussion

• Over time, perhaps, we are unable to tell the difference between information processed during perception and information received later.

Implications

• If eye witnesses are so inaccurate then we must not allow a person to be convicted just on the basis of an eye witness report.

• Leading questions in court should also be avoided.

Criticisms

• Lacks ecological validity - not a real crash, paying attention

• Participants - students, young and intelligent, eager to please their lecturers

• Demand characteristics - they knew they were being studied

• May not be memory but just guess work based on information supplied